Classical Greece was a period of around 200 years (5th and 4th centuries BC) in Greek culture.[1] This Classical period saw the annexation of much of modern-day Greece by the Persian Empire[2] and its subsequent independence. Classical Greece had a powerful influence on the Roman Empire and on the foundations of Western civilization. Much of modern Western politics, artistic thought (architecture, sculpture), scientific thought, theatre, literature, and philosophy derives from this period of Greek history. In the context of the art, architecture, and culture of Ancient Greece, the Classical period[3] corresponds to most of the 5th and 4th centuries BC (the most common dates being the fall of the last Athenian tyrant in 510 BC and the death of Alexander the Great in 323 BC). The Classical period in this sense follows the Archaic period and is in turn succeeded by the Hellenistic period.
5th century BC

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This century is essentially studied from the Athenian outlook because Athens has left us more narratives, plays, and other written works than the other ancient Greek states. From the perspective of Athenian culture in Classical Greece, the period generally referred to as the 5th century BC extends slightly into the 4th century BC. In this context, one might consider that the first significant event of this century occurs in 508 BC, with the fall of the last Athenian tyrant and Cleisthenes' reforms. However, a broader view of the whole Greek world might place its beginning at the Ionian Revolt of 500 BC, the event that provoked the Persian invasion of 492 BC. The Persians were defeated in 490 BC. A second Persian attempt, in 481–479 BC, failed as well, despite having overrun much of modern-day Greece (north of the Isthmus of Corinth) at a crucial point during the war following the Battle of Thermopylae and the Battle of Artemisium.[2][4] The Delian League then formed, under Athenian hegemony and as Athens' instrument. Athens' excesses caused several revolts among the allied cities, all of which were put down by force, but Athenian dynamism finally awoke Sparta and brought about the Peloponnesian War in 431 BC. After both forces were spent, a brief peace came about; then the war resumed to Sparta's advantage. Athens was definitively defeated in 404 BC, and internal Athenian agitations mark the end of the 5th century BC in Greece.
Since its beginning, Sparta had been ruled by a diarchy. This meant that Sparta had two kings ruling concurrently throughout its entire history. The two kingships were both hereditary, vested in the Agiad dynasty and the Eurypontid dynasty. According to legend, the respective hereditary lines of these two dynasties sprang from Eurysthenes and Procles, twin descendants of Hercules. They were said to have conquered Sparta two generations after the Trojan War.
Athens under Cleisthenes

In 510 BC, Spartan troops helped the Athenians overthrow their king, the tyrant Hippias, son of Peisistratos. Cleomenes I, king of Sparta, put in place a pro-Spartan oligarchy headed by Isagoras. But his rival Cleisthenes, with the support of the middle class and aided by democrats, took over. Cleomenes intervened in 508 and 506 BC, but could not stop Cleisthenes, now supported by the Athenians. Through Cleisthenes' reforms, the people endowed their city with isonomic institutions — equal rights for all citizens (though only men were citizens)—and established ostracism.
The isonomic and isegoric (equal freedom of speech)[5] democracy was first organized into about 130 demes, which became the basic civic element. The 10,000 citizens exercised their power as members of the assembly (ἐκκλησία, ekklesia), headed by a council of 500 citizens chosen at random.
The city's administrative geography was reworked, in order to create mixed political groups: not federated by local interests linked to the sea, to the city, or to farming, whose decisions (e.g. a declaration of war) would depend on their geographical position. The territory of the city was also divided into thirty trittyes as follows:
ten trittyes in the coastal region (παρᾰλία, paralia)
ten trittyes in the ἄστυ (astu), the urban centre
ten trittyes in the rural interior, (μεσογεία, mesogia).
A tribe consisted of three trittyes, selected at random, one from each of the three groups. Each tribe therefore always acted in the interest of all three sectors.
It was this corpus of reforms that allowed the emergence of a wider democracy in the 460s and 450s BC.
The Persian wars

In Ionia (the modern Aegean coast of Turkey), the Greek cities, which included great centres such as Miletus and Halicarnassus, were unable to maintain their independence and came under the rule of the Persian Empire in the mid-6th century BC. In 499 BC that region's Greeks rose in the Ionian Revolt, and Athens and some other Greek cities sent aid, but were quickly forced to back down after defeat in 494 BC at the Battle of Lade. Asia Minor returned to Persian control.
In 492 BC, the Persian general Mardonius led a campaign through Thrace and Macedonia. He was victorious and again subjugated the former and conquered the latter,[6] but he was wounded and forced to retreat back into Asia Minor. In addition, a fleet of around 1,200 ships that accompanied Mardonius on the expedition was wrecked by a storm off the coast of Mount Athos. Later, the generals Artaphernes and Datis led a successful naval expedition against the Aegean islands.
In 490 BC, Darius the Great, having suppressed the Ionian cities, sent a Persian fleet to punish the Greeks. (Historians are uncertain about their number of men; accounts vary from 18,000 to 100,000.) They landed in Attica intending to take Athens, but were defeated at the Battle of Marathon by a Greek army of 9,000 Athenian hoplites and 1,000 Plataeans led by the Athenian general Miltiades. The Persian fleet continued to Athens but, seeing it garrisoned, decided not to attempt an assault.
In 480 BC, Darius' successor Xerxes I sent a much more powerful force of 300,000 by land, with 1,207 ships in support, across a double pontoon bridge over the Hellespont. This army took Thrace, before descending on Thessaly and Boeotia, whilst the Persian navy skirted the coast and resupplied the ground troops. The Greek fleet, meanwhile, dashed to block Cape Artemision. After being delayed by Leonidas I, the Spartan king of the Agiad Dynasty, at the Battle of Thermopylae (a battle made famous by the 300 Spartans who faced the entire Persian army), Xerxes advanced into Attica, and captured and burned Athens. The subsequent Battle of Artemisium resulted in the capture of Euboea, bringing most of mainland Greece north of the Isthmus of Corinth under Persian control.[2][4] However, the Athenians had evacuated the city of Athens by sea before Thermopylae, and under the command of Themistocles, they defeated the Persian fleet at the Battle of Salamis.

In 483 BC, during the period of peace between the two Persian invasions, a vein of silver ore had been discovered in the Laurion (a small mountain range near Athens), and the hundreds of talents mined there were used to build 200 warships to combat Aeginetan piracy. A year later, the Greeks, under the Spartan Pausanias, defeated the Persian army at Plataea. The Persians then began to withdraw from Greece, and never attempted an invasion again.
The Athenian fleet then turned to chasing the Persians from the Aegean Sea, defeating their fleet decisively in the Battle of Mycale; then in 478 BC the fleet captured Byzantium. At that time Athens enrolled all the island states and some mainland ones into an alliance called the Delian League, so named because its treasury was kept on the sacred island of Delos. The Spartans, although they had taken part in the war, withdrew into isolation afterwards, allowing Athens to establish unchallenged naval and commercial power.
The Peloponnesian war

Origins of the Delian League and the Peloponnesian League
In 431 BC war broke out between Athens and Sparta. The war was a struggle not merely between two city-states but rather between two coalitions, or leagues of city-states:[7]  the Delian League, led by Athens, and the Peloponnesian League, led by Sparta.
Delian league
The Delian League grew out of the need to present a unified front of all Greek city-states against Persian aggression. In 481 BC, Greek city-states, including Sparta, met in the first of a series of "congresses" that strove to unify all the Greek city-states against the danger of another Persian invasion.[8] The coalition that emerged from the first congress was named the "Hellenic League" and included Sparta. Persia, under Xerxes, invaded Greece in September 481 BC, but the Athenian navy defeated the Persian navy. The Persian land forces were delayed in 480 BC by a much smaller force of 300 Spartans, 400 Thebans and 700 men from Boeotian Thespiae at the Battle of Thermopylae.[9] The Persians left Greece in 479 BC after their defeat at Plataea.[10]
Plataea was the final battle of Xerxes' invasion of Greece. After this, the Persians never again tried to invade Greece. With the disappearance of this external threat, cracks appeared in the united front of the Hellenic League.[11] In 477, Athens became the recognised leader of a coalition of city-states that did not include Sparta. This coalition met and formalized their relationship at the holy city of Delos.[12] Thus, the League took the name "Delian League". Its formal purpose was to liberate Greek cities still under Persian control.[13] However, it became increasingly apparent that the Delian League was really a front for Athenian hegemony throughout the Aegean.[14]
Peloponnesian (or Spartan) league
A competing coalition of Greek city-states centred around Sparta arose, and became more important as the external Persian threat subsided. This coalition is known as the Peloponnesian League. However, unlike the Hellenic League and the Delian League, this league was not a response to any external threat, Persian or otherwise: it was unabashedly an instrument of Spartan policy aimed at Sparta's security and Spartan dominance over the Peloponnese peninsula.[15] The term "Peloponnesian League" is a misnomer. It was not really a "league" at all. Nor was it really "Peloponnesian".[15] There was no equality at all between the members, as might be implied by the term "league". Furthermore, most of its members were located outside the Peloponnese Peninsula.[15] The terms "Spartan League" and "Peloponnesian League" are modern terms. Contemporaries instead referred to "Lacedaemonians and their Allies" to describe the "league".[15]
The league had its origins in Sparta's conflict with Argos, another city on the Peloponnese Peninsula. In the 7th century BC, Argos dominated the peninsula. Even in the early 6th century, the Argives attempted to control the northeastern part of the peninsula. The rise of Sparta in the 6th century brought Sparta into conflict with Argos. However, with the conquest of the Peloponnesian city-state of Tegea in 550 BC and the defeat of the Argives in 546 BC, the Spartans' control began to reach well beyond the borders of Laconia.
The thirty years peace

As the two coalitions grew, their separate interests kept coming into conflict. Under the influence of King Archidamus II (the Eurypontid king of Sparta from 476 BC through 427 BC), Sparta, in the late summer or early autumn of 446 BC, concluded the Thirty Years Peace with Athens.  This treaty took effect the next winter in 445 BC[16]  Under the terms of this treaty, Greece was formally divided into two large power zones.[17] Sparta and Athens agreed to stay within their own power zone and not to interfere in the other's. Despite the Thirty Years Peace, it was clear that war was inevitable.[18]  As noted above, at all times during its history down to 221 BC, Sparta was a "diarchy" with two kings ruling the city-state concurrently.  One line of hereditary kings was from the Eurypontid Dynasty while the other king was from the Agiad Dynasty.  With the signing of the Thirty Years Peace treaty Archidamus II felt he had successfully prevented Sparta from entering into a war with its neighbours.[19]  However, the strong war party in Sparta soon won out and in 431 BC Archidamus was forced to go to war with the Delian League.  However, in 427 BC, Archidamus II died and his son, Agis II succeeded to the Eurypontid throne of Sparta.[20]
Causes of the Peloponnesian war
The immediate causes of the Peloponnesian War vary from account to account. However three causes are fairly consistent among the ancient historians, namely Thucydides and Plutarch. Prior to the war, Corinth and one of its colonies, Corcyra (modern-day Corfu), went to war in 435 BC over the new Corcyran colony of Epidamnus.[21]  Sparta refused to become involved in the conflict and urged an arbitrated settlement of the struggle.[22]  In 433 BC, Corcyra sought Athenian assistance in the war.  Corinth was known to be a traditional enemy of Athens.  However, to further encourage Athens to enter the conflict, Corcyra pointed out how useful a friendly relationship with Corcyra would be, given the strategic locations of Corcyra itself and the colony of Epidamnus on the east shore of the Adriatic Sea.[23] Furthermore, Corcyra promised that Athens would have the use of Corcyra's navy, the third-largest in Greece. This was too good of an offer for Athens to refuse. Accordingly, Athens signed a defensive alliance with Corcyra.
The next year, in 432 BC, Corinth and Athens argued over control of Potidaea (near modern-day Nea Potidaia), eventually leading to an Athenian siege of Potidaea.[24]  In 434–433 BC Athens issued the "Megarian Decrees", a series of decrees that placed economic sanctions on the Megarian people.[25] The Peloponnesian League accused Athens of violating the Thirty Years Peace through all of the aforementioned actions, and, accordingly, Sparta formally declared war on Athens.
Many historians consider these to be merely the immediate causes of the war. They would argue that the underlying cause was the growing resentment on the part of Sparta and its allies at the dominance of Athens over Greek affairs. The war lasted 27 years, partly because Athens (a naval power) and Sparta (a land-based military power) found it difficult to come to grips with each other.
The Peloponnesian war: Opening stages (431–421 BC)
Sparta's initial strategy was to invade Attica, but the Athenians were able to retreat behind their walls. An outbreak of plague in the city during the siege caused many deaths, including that of Pericles. At the same time the Athenian fleet landed troops in the Peloponnesus, winning battles at Naupactus (429) and Pylos (425). However, these tactics could bring neither side a decisive victory. After several years of inconclusive campaigning, the moderate Athenian leader Nicias concluded the Peace of Nicias (421).

The Peloponnesian war:  Second phase (418–404 BC)
In 418 BC, however, conflict between Sparta and the Athenian ally Argos led to a resumption of hostilities. Alcibiades was one of the most influential voices in persuading the Athenians to ally with Argos against the Spartans.[26] At the Mantinea Sparta defeated the combined armies of Athens and her allies. Accordingly, Argos and the rest of the Peloponnesus was brought back under the control of Sparta.[26]  The return of peace allowed Athens to be diverted from meddling in the affairs of the Peloponnesus and to concentrate on building up the empire and putting their finances in order. Soon trade recovered and tribute began, once again, rolling into Athens.[26] A strong "peace party" arose, which promoted avoidance of war and continued concentration on the economic growth of the Athenian Empire.  Concentration on the Athenian Empire, however, brought Athens into conflict with another Greek state.
The Melian expedition (416 BC)
Ever since the formation of the Delian League in 477 BC, the island of Melos had refused to join. By refusing to join the League, however, Melos reaped the benefits of the League without bearing any of the burdens.[27] In 425 BC, an Athenian army under Cleon attacked Melos to force the island to join the Delian League. However, Melos fought off the attack and was able to maintain its neutrality.[27] Further conflict was inevitable and in the spring of 416 BC the mood of the people in Athens was inclined toward military adventure. The island of Melos provided an outlet for this energy and frustration for the military party. Furthermore, there appeared to be no real opposition to this military expedition from the peace party. Enforcement of the economic obligations of the Delian League upon rebellious city-states and islands was a means by which continuing trade and prosperity of Athens could be assured. Melos alone among all the Cycladic Islands located in the south-west Aegean Sea had resisted joining the Delian League.[27] This continued rebellion provided a bad example to the rest of the members of the Delian League.
The debate between Athens and Melos over the issue of joining the Delian League is presented by Thucydides in his Melian Dialogue.[28] The debate did not in the end resolve any of the differences between Melos and Athens and Melos was invaded in 416 BC, and soon occupied by Athens. This success on the part of Athens whetted the appetite of the people of Athens for further expansion of the Athenian Empire.[29]  Accordingly, the people of Athens were ready for military action and tended to support the  military party, led by Alcibiades.
The Sicilian expedition (415–413 BC)

Thus, in 415 BC, Alcibiades found support within the Athenian Assembly for his position when he urged that Athens launch a major expedition against Syracuse, a Peloponnesian ally in Sicily.[30]  Segesta, a town in Sicily, had requested Athenian assistance in their war with another Sicilian town— the town of Selinus. Although Nicias was a sceptic about the Sicilian Expedition, he was appointed along with Alcibiades to lead the expedition.[31]

However, unlike the expedition against Melos, the citizens of Athens were deeply divided over Alcibiades' proposal for an expedition to far-off Sicily. In June 415 BC, on the very eve of the departure of the Athenian fleet for Sicily, a band of vandals in Athens defaced the many statues of the god Hermes that were scattered throughout the city of Athens.[32] This action was blamed on Alcibiades and was seen as a bad omen for the coming campaign.[33]  In all likelihood, the coordinated action against the statues of Hermes was the action of the peace party.[34]  Having lost the debate on the issue, the peace party was desperate to weaken Alcibiades' hold on the people of Athens. Successfully blaming Alcibiades for the action of the vandals would have weakened Alcibiades and the war party in Athens.  Furthermore, it is unlikely that Alcibiades would have deliberately defaced the statues of Hermes on the very eve of his departure with the fleet. Such defacement could only have been interpreted as a bad omen for the expedition that he had long advocated.
Even before the fleet reached Sicily, word arrived to the fleet that Alcibiades was to be arrested and charged with sacrilege of the statues of Hermes, prompting Alcibiades to flee to Sparta.[35]  When the fleet later landed in Sicily and the battle was joined, the expedition was a complete disaster. The entire expeditionary force was lost and Nicias was captured and executed. This was one of the most crushing defeats in the history of Athens.
Alcibiades in Sparta
Meanwhile, Alcibiades betrayed Athens and became a chief advisor to the Spartans and began to counsel them on the best way to defeat his native land. Alcibiades persuaded the Spartans to begin building a real navy for the first time— large enough to challenge the Athenian superiority at sea. Additionally, Alcibiades persuaded the Spartans to ally themselves with their traditional foes— the Persians.  As noted below, Alcibiades soon found himself in controversy in Sparta when he was accused of having seduced Timaea, the wife of Agis II, the Eurypontid king of Sparta.[20]  Accordingly, Alcibiades was required to flee from Sparta and seek the protection of the Persian Court.
Persia intervenes
In the Persian court, Alcibiades now betrayed both by helping Sparta build a navy commensurate with the Athenian navy. Alcibiades advised that a victory of Sparta over Athens was not in the best interest of the Persian Empire. Rather, long and continuous warfare between Sparta and Athens would weaken both city-states and allow the Persians to dominate the Greek peninsula.
Among the war party in Athens, a belief arose that the catastrophic defeat of the military expedition to Sicily in 415–413 could have been avoided if Alcibiades had been allowed to lead the expedition. Thus, despite his treacherous flight to Sparta and his collaboration with Sparta and later with the Persian court, there arose a demand among the war party that Alcibiades be allowed to return to Athens without being arrested. Alcibiades negotiated with his supporters on the Athenian-controlled island of Samos. Alcibiades felt that "radical democracy" was his worst enemy. Accordingly, he asked his supporters to initiate a coup to establish an oligarchy in Athens. If the coup were successful Alcibiades promised to return to Athens  In 411, a successful oligarchic coup was mounted in Athens, by a group which became known as "the 400". However, a parallel attempt by the 400 to overthrow democracy in Samos failed. Alcibiades was immediately made an admiral (navarch) in the Athenian navy. Later, due to democratic pressures, the 400 were replaced by a broader oligarchy called "the 5000". Alcibiades did not immediately return to Athens. In early 410, Alcibiades led an Athenian fleet of 18 triremes against the Persian-financed Spartan fleet at Abydos near the Hellespont. The Battle of Abydos had actually begun before the arrival of Alcibiades, and had been inclining slightly toward the Athenians. However, with the arrival of Alcibiades, the Athenian victory over the Spartans became a rout. Only the approach of nightfall and the movement of Persian troops to the coast where the Spartans had beached their ships saved the Spartan navy from total destruction.
Following Alcibiades' advice, the Persian Empire had been playing Sparta and Athens off against each other. However, as weak as the Spartan navy was after the Battle of Abydos, the Persian navy directly assisted the Spartans. Alcibiades then pursued and met the combined Spartan and Persian fleets at the Battle of Cyzicus later in the spring of 410, achieving a significant victory.
Lysander and the end of the war
Sparta then built a fleet, with the financial help of the Persians, to challenge Athenian naval supremacy, and found a new military leader in Lysander, who attacked Abydos and seized the strategic initiative by occupying the Hellespont, the source of Athens' grain imports.[36] Threatened with starvation, Athens sent its last remaining fleet to confront Lysander, but he decisively defeated it at Aegospotami (405 BC). The loss of her fleet threatened Athens with bankruptcy. In 404 BC Athens sued for peace, and Sparta dictated a predictably stern settlement: Athens lost her city walls, her fleet, and all of her overseas possessions. Lysander abolished the democracy and appointed in its place an oligarchy called the "Thirty Tyrants" to govern Athens.
Meanwhile, in Sparta, Timaea gave birth to a child. The child was given the name Leotychidas, after the great grandfather of Agis II— King Leotychidas of Sparta. However, because of Timaea's alleged affair with Alcibiades, it was widely rumoured that the young Leotychidas was fathered by Alcibiades.[20] Indeed, Agis II refused to acknowledge Leotychidas as his son until he relented, in front of witnesses, on his deathbed in 400 BC.[37]
Upon the death of Agis II, Leotychidas attempted to claim the Eurypontid throne for himself, but this was met with an outcry, led by Lysander, who was at the height of his influence in Sparta.[37] Lysander argued that Leotychidas was a bastard and could not inherit the Eurypontid throne;[37] instead he backed the hereditary claim of Agesilaus, son of Agis by another wife. With Lysander's support, Agesilaus became the Eurypontid king as Agesilaus II, expelled Leotychidas from the country, and took over all of Agis' estates and property.
4th century BC
Related articles: Spartan hegemony and Theban hegemony

The end of the Peloponnesian War left Sparta the master of Greece, but the narrow outlook of the Spartan warrior elite did not suit them to this role.[38] Within a few years the democratic party regained power in Athens and in other cities. In 395 BC the Spartan rulers removed Lysander from office, and Sparta lost her naval supremacy. Athens, Argos, Thebes, and Corinth, the latter two former Spartan allies, challenged Sparta's dominance in the Corinthian War, which ended inconclusively in 387 BC. That same year Sparta shocked the Greeks by concluding the Treaty of Antalcidas with Persia. The agreement turned over the Greek cities of Ionia and Cyprus, reversing a hundred years of Greek victories against Persia. Sparta then tried to further weaken the power of Thebes, which led to a war in which Thebes allied with its old enemy Athens.
Then the Theban generals Epaminondas and Pelopidas won a decisive victory at Leuctra (371 BC). The result of this battle was the end of Spartan supremacy and the establishment of Theban dominance, but Athens herself recovered much of her former power because the supremacy of Thebes was short-lived. With the death of Epaminondas at Mantinea (362 BC) the city lost its greatest leader and his successors blundered into an ineffectual ten-year war with Phocis. In 346 BC the Thebans appealed to Philip II of Macedon to help them against the Phocians, thus drawing Macedon into Greek affairs for the first time.[39]
The Peloponnesian War was a radical turning point for the Greek world. Before 403 BC, the situation was more defined, with Athens and its allies (a zone of domination and stability, with a number of island cities benefiting from Athens' maritime protection), and other states outside this Athenian Empire. The sources denounce this Athenian supremacy (or hegemony) as smothering and disadvantageous.[40]
After 403 BC, things became more complicated, with a number of cities trying to create similar empires over others, all of which proved short-lived. The first of these turnarounds was managed by Athens as early as 390 BC, allowing it to re-establish itself as a major power without regaining its former glory.
The fall of Sparta
This empire was powerful but short-lived. In 405 BC, the Spartans were masters of all – of Athens' allies and of Athens itself – and their power was undivided. By the end of the century, they could not even defend their own city.  As noted above, in 400 BC, Agesilaus became king of Sparta.[41]
Foundation of a Spartan empire
The subject of how to reorganize the Athenian Empire as part of the Spartan Empire provoked much heated debate among Sparta's full citizens. The admiral Lysander felt that the Spartans should rebuild the Athenian empire in such a way that Sparta profited from it. Lysander tended to be too proud to take advice from others.[42]  Prior to this, Spartan law forbade the use of all precious metals by private citizens, with transactions being carried out with cumbersome iron ingots (which generally discouraged their accumulation) and all precious metals obtained by the city becoming state property. Without the Spartans' support, Lysander's innovations came into effect and brought a great deal of profit for him – on Samos, for example, festivals known as Lysandreia were organized in his honour. He was recalled to Sparta, and once there did not attend to any important matters.

Sparta refused to see Lysander or his successors dominate. Not wanting to establish a hegemony, they decided after 403 BC not to support the directives that he had made.
Agesilaus came to power by accident at the start of the 4th century BC. This accidental accession meant that, unlike the other Spartan kings, he had the advantage of a Spartan education. The Spartans at this date discovered a conspiracy against the laws of the city conducted by Cinadon and as a result concluded there were too many dangerous worldly elements at work in the Spartan state.
Agesilaus employed a political dynamic that played on a feeling of pan-Hellenic sentiment and launched a successful campaign against the Persian empire.[43] Once again, the Persian empire played both sides against each other.  The Persian Court supported Sparta in the rebuilding of their navy while simultaneously funding the Athenians, who used Persian subsidies to rebuild their long walls (destroyed in 404 BC) as well as to reconstruct their fleet and win a number of victories.
For most of the first years of his reign, Agesilaus had been engaged in a war against Persia in the Aegean Sea and in Asia Minor.[44]  In 394 BC, the Spartan authorities ordered Agesilaus to return to mainland Greece.  While Agesilaus had a large part of the Spartan Army in Asia Minor, the Spartan forces protecting the homeland had been attacked by a coalition of forces led  by Corinth.[45]  At the Battle of Haliartus the Spartans had been defeated by the Theban forces.  Worse yet, Lysander, Sparta's chief military leader, had been killed during the battle.[46]   This was the start of what became known as the "Corinthian War" (395 BC – 387 BC).[43]  Upon hearing of the Spartan loss at Haliartus and of the death of Lysander, Agesilaus headed out of Asia Minor, back across the Hellespont, across Thrace and back towards Greece.  At the Battle of Coronea, Agesilaus and his Spartan Army defeated a Theban force. During the war, Corinth drew support from a coalition of traditional Spartan enemies— Argos, Athens and Thebes.[47]  However, when the war descended into guerilla tactics, Sparta decided that it could not fight on two fronts and so chose to ally with Persia.[47] The long Corinthian War finally ended with the Peace of Antalcidas or the King's Peace, in which the "Great King" of Persia, Artaxerxes II, pronounced a "treaty" of peace between the various city-states of Greece which broke up all "leagues" of city-states on Greek mainland and in the islands of the Aegean Sea. Although this was looked upon as "independence" for some city-states, the effect of the unilateral "treaty" was highly favourable to the interests of the Persian Empire.
The Corinthian War revealed a significant dynamic that was occurring in Greece.  While Athens and Sparta fought each other to exhaustion, Thebes was rising to a position of dominance among the various Greek city-states.
The peace of Antalcidas
In 387 BC, an edict was promulgated by the Persian king, preserving the Greek cities of Asia Minor and Cyprus as well as the independence of the Greek Aegean cities, except for Lymnos, Imbros and Skyros, which were given over to Athens.[48]  It dissolved existing alliances and federations and forbade the formation of new ones. This is an ultimatum that benefited Athens only to the extent that Athens held onto three islands. While the "Great King," Artaxerxes, was the guarantor of the peace, Sparta was to act as Persia's agent in enforcing the Peace.[49] To the Persians this document is known as the "King's Peace." To the Greeks, this document is known as the Peace of Antalcidas, after the Antalcidas who was sent to Persia as negotiator. Sparta had been worried about the developing closer ties between Athens and Persia. Accordingly, Antalcidas was directed to get whatever agreement he could from the "Great King". Accordingly, the "Peace of Antalcidas" is not a negotiated peace at all. Rather it is a surrender to the interests of Persia, drafted entirely for its benefit.[49]
Spartan interventionism
On the other hand, this peace had unexpected consequences. In accordance with it, the Boeotian League, or Boeotian confederacy, was dissolved in 386 BC.[50] This confederacy was dominated by Thebes, a city hostile to the Spartan hegemony.  Sparta carried out large-scale operations and peripheral interventions in Epirus and in the north of Greece, resulting in the capture of the fortress of Thebes, the Cadmea, after an expedition in the Chalcidice and the capture of Olynthos.  It was a Theban politician who suggested to the Spartan general Phoibidas that Sparta should seize Thebes itself. This act was sharply condemned, though Sparta eagerly ratified this unilateral move by Phoibidas.  The Spartan attack was successful and Thebes was placed under Spartan control.[51]
Clash with Thebes
In 378 BC, the reaction to Spartan control over Thebes was broken by a popular uprising within Thebes.  Elsewhere in Greece, the reaction against Spartan hegemony began when Sphodrias, another Spartan general, tried to carry out a surprise attack on Piraeus.[52] Although the gates of Piraeus were no longer fortified, Sphodrias was driven off before Piraeus. Back in Sparta, Sphodrias was put on trial for the failed attack, but was acquitted by the Spartan court. Nonetheless, the attempted attack triggered an alliance between Athens and Thebes.[52] Sparta would now have to fight them both together. Athens was trying to recover from its defeat in the Peloponnesian War at the hands of Sparta's "navarch" Lysander in the disaster of 404 BC. The rising spirit of rebellion against Sparta also fueled Thebes' attempt to restore the former Boeotian confederacy.[53]  In Boeotia, the Theban leaders Pelopidas and Epaminondas reorganized the Theban army and began to free the towns of Boeotia from their Spartan garrisons, one by one, and incorporated these towns into the revived Boeotian League.[49] Pelopidas won a great victory for Thebes over a much larger Spartan force in the Battle of Tegyra in 375 BC.[54]
Theban authority grew so spectacularly in such a short time that Athens came to mistrust the growing Theban power. Athens began to consolidate its position again through the formation of a second Athenian League.[55]  Attention was drawn to growing power of Thebes when it began interfering in the political affairs of its neighbor, Phocis, and, particularly, after Thebes razed the city of Plataea, a long-standing ally of Athens, in 375 BC.[56] The destruction of Plataea caused Athens to negotiate an alliance with Sparta against Thebes, in that same year.[56] In 371, the Theban army, led by Epaminondas, inflicted a bloody defeat on Spartan forces at Battle of Leuctra. Sparta lost a large part of its army and 400 of its 2,000 citizen-troops. The Battle of Leuctra was a watershed in Greek history.[56] Epaminondas' victory ended a long history of Spartan military prestige and dominance over Greece and the period of Spartan hegemony was over. However, Spartan hegemony was not replaced by Theban, but rather by Athenian hegemony.
The rise of Athens

Financing the league
It was important to erase the bad memories of the former league. Its financial system was not adopted, with no tribute being paid. Instead, syntaxeis were used, irregular contributions as and when Athens and its allies needed troops, collected for a precise reason and spent as quickly as possible. These contributions were not taken to Athens— unlike the 5th century BC system, there was no central exchequer for the league— but to the Athenian generals themselves.
The Athenians had to make their own contribution to the alliance, the eisphora. They reformed how this tax was paid, creating a system in advance, the Proseiphora, in which the richest individuals had to pay the whole sum of the tax then be reimbursed by other contributors. This system was quickly assimilated into a liturgy.
Athenian hegemony halted
This league responded to a real and present need. On the ground, however, the situation within the league proved to have changed little from that of the 5th century BC, with Athenian generals doing what they wanted and able to extort funds from the league. Alliance with Athens again looked unattractive and the allies complained.
The main reasons for the eventual failure were structural. This alliance was only valued out of fear of Sparta, which evaporated after Sparta's fall in 371 BC, losing the alliance its sole 'raison d'etre'. The Athenians no longer had the means to fulfill their ambitions, and found it difficult merely to finance their own navy, let alone that of an entire alliance, and so could not properly defend their allies. Thus, the tyrant of Pherae was able to destroy a number of cities with impunity. From 360 BC, Athens lost its reputation for invincibility and a number of allies (such as Byzantium and Naxos in 364 BC) decided to secede.
In 357 BC the revolt against the league spread, and between 357 BC and 355 BC, Athens had to face war against its allies—a war whose issue was marked by a decisive intervention by the king of Persia in the form of an ultimatum to Athens, demanding that Athens recognise its allies' independence under threat of Persia's sending 200 triremes against Athens. Athens had to renounce the war and leave the confederacy, thereby weakening itself more and more, and signaling the end of Athenian hegemony.
Theban hegemony – tentative and with no future
5th century BC Boeotian confederacy (447–386 BC)
This was not Thebes' first attempt at hegemony. It had been the most important city of Boeotia and the centre of the previous Boeotian confederacy of 447, resurrected since 386.
The 5th-century confederacy is well known to us from a papyrus found at Oxyrhynchus and known as "the Anonyme of Thebes". Thebes headed it and set up a system under which charges were divided up between the different cities of the confederacy. Citizenship was defined according to wealth, and Thebes counted 11,000 active citizens.
The confederacy was divided up into 11 districts, each providing a federal magistrate called a "boeotarch", a certain number of council members, 1,000 hoplites and 100 horsemen. From the 5th century BC the alliance could field an infantry force of 11,000 men, in addition to an elite corps and a light infantry numbering 10,000; but its real power derived from its cavalry force of 1,100, commanded by a federal magistrate independent of local commanders. It also had a small fleet that played a part in the Peloponnesian War by providing 25 triremes for the Spartans. At the end of the conflict, the fleet consisted of 50 triremes and was commanded by a "navarch".
All this constituted a significant enough force that the Spartans were happy to see the Boeotian confederacy dissolved by the king's peace. This dissolution, however, did not last, and in the 370s there was nothing to stop the Thebans (who had lost the Cadmea to Sparta in 382 BC) from reforming this confederacy.
Theban reconstruction
Pelopidas and Epaminondas endowed Thebes with democratic institutions similar to those of Athens, the Thebans revived the title of "Boeotarch" lost in the Persian King's Peace and – with victory at Leuctra and the destruction of Spartan power – the pair achieved their stated objective of renewing the confederacy. Epaminondas rid the Peloponnesus of pro-Spartan oligarchies, replacing them with pro-Theban democracies, constructed cities, and rebuilt a number of those destroyed by Sparta. He equally supported the reconstruction of the city of Messene thanks to an invasion of Laconia that also allowed him to liberate the helots and give them Messene as a capital.
He decided in the end to constitute small confederacies all round the Peloponnessus, forming an Arcadian confederacy (the King's Peace had destroyed a previous Arcadian confederacy and put Messene under Spartan control).
Confrontation between Athens and Thebes
The strength of the Boeotian League explains Athens' problems with her allies in the second Athenian League.  Epaminondas succeeded in convincing his countrymen to build a fleet of 100 triremes to pressure cities into leaving the Athenian league and joining a Boeotian maritime league. Epaminondas and Pelopidas also reformed the army of Thebes to introduce new and more effective means of fighting.  Thus, the Theban army was able to carry the day against the coalition of other Greek states at the battle of Leuctra in 371 BC and the battle of Mantinea in 362 BC.
Sparta also remained an important power in the face of Theban strength. However, some of the cities allied with Sparta turned against her, because of Thebes. In 367 BC, both Sparta and Athens sent delegates to Artaxerxes II, the Great King of Persia. These delegates sought to have the Artaxerxes, once again, declare Greek independence and a unilateral common peace, just as he had done in twenty years earlier in 387 BC.  As noted above, this had meant the destruction of the Boeotian League in 387 BC. Sparta and Athens now hoped the same thing would happen with a new declaration of a similar "Kings Peace". Thebes sent Pelopidas to argue against them.[57]  The Great King was convinced by Pelopidas and the Theban diplomats that Thebes and the Boeotian League would be the best agents of Persian interests in Greece, and, accordingly, did not issue a new "King's Peace."[50] Thus, to deal with Thebes, Athens and Sparta were thrown back on their own resources.  Thebes, meanwhile, expanded its influence beyond the bounds of Boeotia.  In 364 BC, Pelopidas defeated the Alexander of Pherae in the Battle of Cynoscephalae, located in south-eastern Thessaly in northern Greece.  However, during the battle, Pelopides was killed.[58]
The confederational framework of Sparta's relationship with her allies was really an artificial one, since it attempted to bring together cities that had never been able to agree on much at all in the past. Such was the case with the cities of Tegea and Mantinea, which re-allied in the Arcadian confederacy. The Mantineans received the support of the Athenians, and the Tegeans that of the Thebans.  In 362 BC, Epaminondas led a Theban army against a coalition of Athenian, Spartan, Elisian, Mantinean and Achean forces. Battle was joined at Mantinea.[50]  The Thebans prevailed, but this triumph was short-lived, for Epaminondas died in the battle, stating that "I bequeath to Thebes two daughters, the victory of Leuctra and the victory at Mantinea".
Despite the victory at Mantinea, in the end, the Thebans abandoned their policy of intervention in the Peloponnesus.  This event is looked upon as a watershed in Greek history.  Thus, Xenophon concludes his history of the Greek world at this point, in 362 BC. The end of this period was even more confused than its beginning. Greece had failed and, according to Xenophon, the history of the Greek world was no longer intelligible.
The idea of hegemony disappeared. From 362 BC onward, there was no longer a single city that could exert hegemonic power in Greece. The Spartans were greatly weakened; the Athenians were in no condition to operate their navy, and after 365 no longer had any allies; Thebes could only exert an ephemeral dominance, and had the means to defeat Sparta and Athens but not to be a major power in Asia Minor.
Other forces also intervened, such as the Persian king, who appointed himself arbitrator among the Greek cities, with their tacit agreement. This situation reinforced the conflicts and there was a proliferation of civil wars, with the confederal framework a repeated trigger for them. One war led to another, each longer and more bloody than the last, and the cycle could not be broken. Hostilities even took place during winter for the first time, with the invasion of Laconia in 370 BC.
Rise of Macedon

Thebes sought to maintain its position until finally eclipsed by the rising power of Macedon in 346 BC. The energetic leadership within Macedon began in 359 BC when Philip of Macedon was made regent for his nephew, Amyntas. Within a short time, Philip was acclaimed king as Philip II of Macedonia in his own right, with succession of the throne established on his own heirs.[59]  During his lifetime, Philip II consolidated his rule over Macedonia. This was done by 359 BC and Philip began to look toward expanding Macedonia's influence abroad. The dream of restoring Greece to its grandeur by liberating all Greek lands from Persian dominion was alive even in this early stage. This dream even included conquering Persia itself.[60]
Under Philip II, (359–336 BC), Macedon expanded into the territory of the Paeonians, Thracians, and Illyrians.[61] In 358 BC, Philip allied with Epirus in its campaign against Illyria. In 357 BC, Philip came into direct conflict with Athens when he conquered the Thracian port city of Amphipolis, a city located at the mouth of the Strymon River to the east of Macedonia, and a major Athenian trading port.  Conquering this city allowed Philip to subjugate all of Thrace.  A year later in 356 BC, the Macedonians attacked and conquered the Athenian-controlled port city of Pydna.  This brought the Macedonian threat to Athens closer to home to the Athenians. With the start of the Phocian War in 356 BC, the great Athenian orator and political leader of the "war party", Demosthenes, became increasingly active in encouraging Athens to fight vigorously against Philip's expansionist aims.[62]  In 352 BC, Demosthenes gave many speeches against the Macedonian threat, declaring Philip II Athens' greatest enemy.  The leader of the Athenian "peace party" was Phocion, who wished to avoid a confrontation that, Phocion felt, would be catastrophic for Athens.  Despite Phocion's attempts to restrain the war party, Athens remained at war with Macedonia for years following the original declaration of war.[63]  Negotiations between Athens and Philip II started only in 346 BC.[64]  The Athenians successfully halted Philip's invasion of Attica at Thermopylae that same year in 352 BC. However, Philip defeated the Phocians at the Battle of the Crocus Field. The conflict between Macedonia and all the city-states of Greece came to a head in 338 BC,[65] at the Battle of Chaeronea.
The Macedonians became more politically involved with the south-central city-states of Greece, but also retained more archaic aspects harking back to the palace culture, first at Aegae (modern Vergina) then at Pella, resembling Mycenaean culture more than that of the Classical city-states. Militarily, Philip recognized the new phalanx style of fighting that had been employed by Epaminondas and Phielopidas in Thebes.  Accordingly, he incorporated this new system into the Macedonian army.  Philip II also brought a Theban military tutor to Macedon to instruct the future Alexander the Great in the Theban method of fighting.[66]
Philip's son Alexander the Great was born in Pella, Macedonia (356–323 BC). Philip II brought Aristotle to Pella to teach the young Alexander.[67] Besides Alexander's mother, Olympias, Philip took another wife by the name of Cleopatra Eurydice.[68]  Cleopatra had a daughter, Europa, and a son, Caranus. Caranus posed a threat to the succession of Alexander.[69]  Cleopatra Eurydice was a Macedonian and, thus, Caranus was all Macedonian in blood.  Olympias, on the other hand, was from Epicurus and, thus, Alexander was regarded as being only half-Macedonian (Cleopatra Eurydice should not be confused with Cleopatra of Macedon, who was Alexander's full-sister and thus daughter of Philip and Olympias).
Philip II was assassinated at the wedding of his daughter Cleopatra of Macedon with King Alexander I of Epirus in 336 BC.[70]  Philip's son, the future Alexander the Great, immediately claimed the throne of Macedonia by eliminating all the other claimants to the throne, including Caranus and his cousin Amytas.[71]  Alexander was only twenty (20) years of age when he assumed the throne.[72]
Thereafter, Alexander continued his father's plans to conquer all of Greece. He did this by both military might and persuasion. After his victory over Thebes, Alexander traveled to Athens to meet the public directly. Despite Demosthenes' speeches against the Macedonian threat on behalf of the war party of Athens, the public in Athens was still very much divided between the "peace party" and Demosthenes' "war party."  However, the arrival of Alexander charmed the Athenian public.[73] The peace party was strengthened and then a peace between Athens and Macedonia was agreed.[74] This allowed Alexander to move on his and the Greeks' long-held dream of conquest in the east, with a unified and secure Greek state at his back.
In 334 BC, Alexander with about 30,000 infantry soldiers and 5,000 cavalry crossed the Hellespont into Asia. He never returned.[75]  Alexander managed to briefly extend Macedonian power not only over the central Greek city-states, but also to the Persian empire, including Egypt and lands as far east as the fringes of India.[61]  He managed to spread Greek culture throughout the known world.[76]  Alexander the Great died in 323 BC in Babylon during his Asian campaign of conquest.[77]
The Classical period conventionally ends at the death of Alexander the Great in 323 BC and the fragmentation of his empire, divided among the Diadochi,[78] which, in the minds of most scholars, marks the beginning of the Hellenistic period.
Legacy of classical Greece
The legacy of Greece was strongly felt by post-Renaissance European elite, who saw themselves as the spiritual heirs of Greece. Will Durant wrote in 1939 that "excepting machinery, there is hardly anything secular in our culture that does not come from Greece," and conversely "there is nothing in Greek civilization that doesn't illuminate our own".[79]
See also
Classical antiquity
Classics
Art in ancient Greece

Were there any major wars during the Classical period?


Surveying or land surveying is the technique, profession, and science of determining the terrestrial or three-dimensional positions of points and the distances and angles between them. A land surveying professional is called a land surveyor. These points are usually on the surface of the Earth, and they are often used to establish maps and boundaries for ownership, locations, such as building corners or the surface location of subsurface features, or other purposes required by government or civil law, such as property sales.
Surveyors work with elements of geometry, trigonometry, regression analysis, physics, engineering, metrology, programming languages, and the law. They use equipment, such as total stations, robotic total stations, theodolites, GPS receivers, retroreflectors, 3D scanners, radios, handheld tablets, digital levels, subsurface locators, drones, GIS, and surveying software.
Surveying has been an element in the development of the human environment since the beginning of recorded history. The planning and execution of most forms of construction require it. It is also used in transport, communications, mapping, and the definition of legal boundaries for land ownership. It is an important tool for research in many other scientific disciplines.
Definition
The International Federation of Surveyors defines the function of surveying as:[1]

A surveyor is a professional person with the academic qualifications and technical expertise to conduct one, or more, of the following activities;
to determine, measure and represent land, three-dimensional objects, point-fields and trajectories;
to assemble and interpret land and geographically related information,
to use that information for the planning and efficient administration of the land, the sea and any structures thereon; and,
to conduct research into the above practices and to develop them.

History

Ancient surveying

Surveying has occurred since humans built the first large structures. In ancient Egypt, a rope stretcher would use simple geometry to re-establish boundaries after the annual floods of the Nile River. The almost perfect squareness and north-south orientation of the Great Pyramid of Giza, built c. 2700 BC, affirm the Egyptians' command of surveying. The Groma instrument originated in Mesopotamia (early 1st millennium BC).[2] The prehistoric monument at Stonehenge (c. 2500 BC) was set out by prehistoric surveyors using peg and rope geometry.[3]
The mathematician Liu Hui described ways of measuring distant objects in his work Haidao Suanjing or The Sea Island Mathematical Manual, published in 263 AD.
The Romans recognized land surveying as a profession. They established the basic measurements under which the Roman Empire was divided, such as a tax register of conquered lands (300 AD).[4] Roman surveyors were known as Gromatici.
In medieval Europe, beating the bounds maintained the boundaries of a village or parish. This was the practice of gathering a group of residents and walking around the parish or village to establish a communal memory of the boundaries. Young boys were included to ensure the memory lasted as long as possible.
In England, William the Conqueror commissioned the Domesday Book in 1086. It recorded the names of all the land owners, the area of land they owned, the quality of the land, and specific information of the area's content and inhabitants. It did not include maps showing exact locations.
Modern surveying

Abel Foullon described a plane table in 1551, but it is thought that the instrument was in use earlier as his description is of a developed instrument.
Gunter's chain was introduced in 1620 by English mathematician Edmund Gunter. It enabled plots of land to be accurately surveyed and plotted for legal and commercial purposes.
Leonard Digges described a Theodolite that measured horizontal angles in his book A geometric practice named Pantometria (1571). Joshua Habermel (Erasmus Habermehl) created a theodolite with a compass and tripod in 1576. Johnathon Sission was the first to incorporate a telescope on a theodolite in 1725.[5]
In the 18th century, modern techniques and instruments for surveying began to be used. Jesse Ramsden introduced the first precision theodolite in 1787. It was an instrument for measuring angles in the horizontal and vertical planes. He created his great theodolite using an accurate dividing engine of his own design. Ramsden's theodolite represented a great step forward in the instrument's accuracy. William Gascoigne invented an instrument that used a telescope with an installed crosshair as a target device, in 1640. James Watt developed an optical meter for the measuring of distance in 1771; it measured the parallactic angle from which the distance to a point could be deduced.
Dutch mathematician Willebrord Snellius (a.k.a. Snel van Royen) introduced the modern systematic use of triangulation. In 1615 he surveyed the distance from Alkmaar to Breda, approximately 72 miles (116,1 kilometres). He underestimated this distance by 3.5%. The survey was a chain of quadrangles containing 33 triangles in all. Snell showed how planar formulae could be corrected to allow for the curvature of the earth. He also showed how to resection, or calculate, the position of a point inside a triangle using the angles cast between the vertices at the unknown point. These could be measured more accurately than bearings of the vertices, which depended on a compass. His work established the idea of surveying a primary network of control points, and locating subsidiary points inside the primary network later. Between 1733 and 1740, Jacques Cassini and his son César undertook the first triangulation of France. They included a re-surveying of the meridian arc, leading to the publication in 1745 of the first map of France constructed on rigorous principles. By this time triangulation methods were well established for local map-making.

It was only towards the end of the 18th century that detailed triangulation network surveys mapped whole countries. In 1784, a team from General William Roy's Ordnance Survey of Great Britain began the Principal Triangulation of Britain. The first Ramsden theodolite was built for this survey. The survey was finally completed in 1853. The Great Trigonometric Survey of India began in 1801. The Indian survey had an enormous scientific impact. It was responsible for one of the first accurate measurements of a section of an arc of longitude, and for measurements of the geodesic anomaly. It named and mapped Mount Everest and the other Himalayan peaks. Surveying became a professional occupation in high demand at the turn of the 19th century with the onset of the Industrial Revolution. The profession developed more accurate instruments to aid its work. Industrial infrastructure projects used surveyors to lay out canals, roads and rail.
In the US, the Land Ordinance of 1785 created the Public Land Survey System. It formed the basis for dividing the western territories into sections to allow the sale of land. The PLSS divided states into township grids which were further divided into sections and fractions of sections.
Napoleon Bonaparte founded continental Europe's first cadastre in 1808. This gathered data on the number of parcels of land, their value, land usage, and names. This system soon spread around Europe.

Robert Torrens introduced the Torrens system in South Australia in 1858. Torrens intended to simplify land transactions and provide reliable titles via a centralized register of land. The Torrens system was adopted in several other nations of the English-speaking world.
Surveying became increasingly important with the arrival of railroads in the 1800s. Surveying was necessary so that railroads could plan technologically and financially viable routes.
20th century

At the beginning of the century surveyors had improved the older chains and ropes, but still faced the problem of accurate measurement of long distances. Dr Trevor Lloyd Wadley developed the Tellurometer during the 1950s. It measures long distances using two microwave transmitter/receivers.[6]
During the late 1950s Geodimeter introduced electronic distance measurement (EDM) equipment.[7] EDM units use a multi frequency phase shift of light waves to find a distance.[8] These instruments saved the need for days or weeks of chain measurement by measuring between points kilometers apart in one go.
Advances in electronics allowed miniaturization of EDM. In the 1970s the first instruments combining angle and distance measurement appeared, becoming known as total stations. Manufacturers added more equipment by degrees, bringing improvements in accuracy and speed of measurement. Major advances include tilt compensators, data recorders, and on-board calculation programs.
The first satellite positioning system was the US Navy TRANSIT system. The first successful launch took place in 1960. The system's main purpose was to provide position information to Polaris missile submarines. Surveyors found they could use field receivers to determine the location of a point. Sparse satellite cover and large equipment made observations laborious, and inaccurate. The main use was establishing benchmarks in remote locations.
The US Air Force launched the first prototype satellites of the Global Positioning System (GPS) in 1978. GPS used a larger constellation of satellites and improved signal transmission to provide more accuracy. Early GPS observations required several hours of observations by a static receiver to reach survey accuracy requirements. Recent improvements to both satellites and receivers allow Real Time Kinematic (RTK) surveying. RTK surveys get high-accuracy measurements by using a fixed base station and a second roving antenna. The position of the roving antenna can be tracked.
21st century
The theodolite, total station, and RTK GPS survey remain the primary methods in use.
Remote sensing and satellite imagery continue to improve and become cheaper, allowing more commonplace use. Prominent new technologies include three-dimensional (3D) scanning and use of lidar for topographical surveys. UAV technology along with photogrammetric image processing is also appearing.
Surveying equipment

Hardware

The main surveying instruments in use around the world are the theodolite, measuring tape, total station, 3D scanners, GPS/GNSS, level and rod. Most instruments screw onto a tripod when in use. Tape measures are often used for measurement of smaller distances. 3D scanners and various forms of aerial imagery are also used.
The theodolite is an instrument for the measurement of angles. It uses two separate circles, protractors or alidades to measure angles in the horizontal and the vertical plane. A telescope mounted on trunnions is aligned vertically with the target object. The whole upper section rotates for horizontal alignment. The vertical circle measures the angle that the telescope makes against the vertical, known as the zenith angle. The horizontal circle uses an upper and lower plate. When beginning the survey, the surveyor points the instrument in a known direction (bearing), and clamps the lower plate in place. The instrument can then rotate to measure the bearing to other objects. If no bearing is known or direct angle measurement is wanted, the instrument can be set to zero during the initial sight. It will then read the angle between the initial object, the theodolite itself, and the item that the telescope aligns with.
The gyrotheodolite is a form of theodolite that uses a gyroscope to orient itself in the absence of reference marks. It is used in underground applications.
The total station is a development of the theodolite with an electronic distance measurement device (EDM). A total station can be used for leveling when set to the horizontal plane. Since their introduction, total stations have shifted from optical-mechanical to fully electronic devices.
Modern top-of-the-line total stations no longer need a reflector or prism to return the light pulses used for distance measurements. They are fully robotic, and can even e-mail point data to a remote computer and connect to satellite positioning systems, such as Global Positioning System. Real Time Kinematic GPS systems have increased the speed of surveying, but they are still only horizontally accurate to about 20mm and vertically to 30–40mm.[9]
GPS surveying differs from other GPS uses in the equipment and methods used. Static GPS uses two receivers placed in position for a considerable length of time. The long span of time lets the receiver compare measurements as the satellites orbit. The changes as the satellites orbit also provide the measurement network with well conditioned geometry. This produces an accurate baseline that can be over 20km long. RTK surveying uses one static antenna and one roving antenna. The static antenna tracks changes in the satellite positions and atmospheric conditions. The surveyor uses the roving antenna to measure the points needed for the survey. The two antennas use a radio link that allows the static antenna to send corrections to the roving antenna. The roving antenna then applies those corrections to the GPS signals it is receiving to calculate its own position. RTK surveying covers smaller distances than static methods. This is because divergent conditions further away from the base reduce accuracy.
Surveying instruments have characteristics that make them suitable for certain uses. Theodolites and levels are often used by constructors rather than surveyors in first world countries. The constructor can perform simple survey tasks using a relatively cheap instrument. Total stations are workhorses for many professional surveyors because they are versatile and reliable in all conditions. The productivity improvements from a GPS on large scale surveys makes them popular for major infrastructure or data gathering projects. One-person robotic-guided total stations allow surveyors to measure without extra workers to aim the telescope or record data. A fast but expensive way to measure large areas is with a helicopter, using a GPS to record the location of the helicopter and a laser scanner to measure the ground. To increase precision, surveyors place beacons on the ground (about 20km (12mi) apart). This method reaches precisions between 5–40cm (depending on flight height).[10]
Surveyors use ancillary equipment such as tripods and instrument stands; staves and beacons used for sighting purposes; PPE; vegetation clearing equipment; digging implements for finding survey markers buried over time; hammers for placements of markers in various surfaces and structures; and portable radios for communication over long lines of sight.
Software
Land surveyors, construction professionals and civil engineers using total station, GPS, 3D scanners and other collector data use Land Surveying Software to increase efficiency, accuracy and productivity. Land Surveying Software is a staple of contemporary land surveying.[11]
Surveying techniques

Surveyors determine the position of objects by measuring angles and distances. The factors that can affect the accuracy of their observations are also measured. They then use this data to create vectors, bearings, coordinates, elevations, areas, volumes, plans and maps. Measurements are often split into horizontal and vertical components to simplify calculation.
GPS and astronomic measurements also need measurement of a time component.
Distance measurement

Before EDM devices, distances were measured using a variety of means. These included chains with links of a known length such as a Gunter's chain, or measuring tapes made of steel or invar. To measure horizontal distances, these chains or tapes were pulled taut to reduce sagging and slack. The distance had to be adjusted for heat expansion. Attempts to hold the measuring instrument level would also be made. When measuring up a slope, the surveyor might have to "break" (break chain) the measurement- use an increment less than the total length of the chain. Perambulators, or measuring wheels, were used to measure longer distances but not to a high level of accuracy. Tacheometry is the science of measuring distances by measuring the angle between two ends of an object with a known size. It was sometimes used before to the invention of EDM where rough ground made chain measurement impractical.
Angle measurement
Historically, horizontal angles were measured by using a compass to provide a magnetic bearing or azimuth. Later, more precise scribed discs improved angular resolution. Mounting telescopes with reticles atop the disc allowed more precise sighting (see theodolite). Levels and calibrated circles allowed measurement of vertical angles. Verniers allowed measurement to a fraction of a degree, such as with a turn-of-the-century transit.
The plane table provided a graphical method of recording and measuring angles, which reduced the amount of mathematics required. In 1829 Francis Ronalds invented a reflecting instrument for recording angles graphically by modifying the octant.[12]
By observing the bearing from every vertex in a figure, a surveyor can measure around the figure. The final observation will be between the two points first observed, except with a 180° difference. This is called a close. If the first and last bearings are different, this shows the error in the survey, called the angular misclose. The surveyor can use this information to prove that the work meets the expected standards.
Levelling

The simplest method for measuring height is with an altimeterusing air pressure to find height. When more precise measurements are needed, means like precise levels (also known as differential leveling) are used. When precise leveling, a series of measurements between two points are taken using an instrument and a measuring rod. Differences in height between the measurements are added and subtracted in a series to get the net difference in elevation between the two endpoints. With the Global Positioning System (GPS), elevation can be measured with satellite receivers. Usually GPS is somewhat less accurate than traditional precise leveling, but may be similar over long distances.
When using an optical level, the endpoint may be out of the effective range of the instrument. There may be obstructions or large changes of elevation between the endpoints. In these situations, extra setups are needed. Turning is a term used when referring to moving the level to take an elevation shot from a different location. To "turn" the level, one must first take a reading and record the elevation of the point the rod is located on. While the rod is being kept in exactly the same location, the level is moved to a new location where the rod is still visible. A reading is taken from the new location of the level and the height difference is used to find the new elevation of the level gun. This is repeated until the series of measurements is completed. The level must be horizontal to get a valid measurement. Because of this, if the horizontal crosshair of the instrument is lower than the base of the rod, the surveyor will not be able to sight the rod and get a reading. The rod can usually be raised up to 25 feet high, allowing the level to be set much higher than the base of the rod.
Determining position
The primary way of determining one's position on the earth's surface when no known positions are nearby is by astronomic observations. Observations to the sun, moon and stars could all be made using navigational techniques. Once the instrument's position and bearing to a star is determined, the bearing can be transferred to a reference point on the earth. The point can then be used as a base for further observations. Survey-accurate astronomic positions were difficult to observe and calculate and so tended to be a base off which many other measurements were made. Since the advent of the GPS system, astronomic observations are rare as GPS allows adequate positions to be determined over most of the surface of the earth.
Reference networks

Few survey positions are derived from first principles. Instead, most surveys points are measured relative to previous measured points. This forms a reference or control network where each point can be used by a surveyor to determine their own position when beginning a new survey.
Survey points are usually marked on the earth's surface by objects ranging from small nails driven into the ground to large beacons that can be seen from long distances. The surveyors can set up their instruments on this position and measure to nearby objects. Sometimes a tall, distinctive feature such as a steeple or radio aerial has its position calculated as a reference point that angles can be measured against.
Triangulation is a method of horizontal location favoured in the days before EDM and GPS measurement. It can determine distances, elevations and directions between distant objects. Since the early days of surveying, this was the primary method of determining accurate positions of objects for topographic maps of large areas. A surveyor first needs to know the horizontal distance between two of the objects, known as the baseline. Then the heights, distances and angular position of other objects can be derived, as long as they are visible from one of the original objects. High-accuracy transits or theodolites were used, and angle measurements repeated for increased accuracy. See also Triangulation in three dimensions.
Offsetting is an alternate method of determining position of objects, and was often used to measure imprecise features such as riverbanks. The surveyor would mark and measure two known positions on the ground roughly parallel to the feature, and mark out a baseline between them. At regular intervals, a distance was measured at right angles from the first line to the feature. The measurements could then be plotted on a plan or map, and the points at the ends of the offset lines could be joined to show the feature.
Traversing is a common method of surveying smaller areas. The surveyor starts from an old reference mark or known position and places a network of reference marks covering the survey area. They then measure bearings and distances between the reference marks, and to the target features. Most traverses form a loop pattern or link between two prior reference marks so the surveyor can check their measurements.
Datum and coordinate systems
Many surveys do not calculate positions on the surface of the earth, but instead measure the relative positions of objects. However, often the surveyed items need to be compared to outside data, such as boundary lines or previous survey's objects. The oldest way of describing a position is via latitude and longitude, and often a height above sea level. As the surveying profession grew it created Cartesian coordinate systems to simplify the mathematics for surveys over small parts of the earth. The simplest coordinate systems assume that the earth is flat and measure from an arbitrary point, known as a 'datum' (singular form of data). The coordinate system allows easy calculation of the distances and direction between objects over small areas. Large areas distort due to the earth's curvature. North is often defined as true north at the datum.
For larger regions, it is necessary to model the shape of the earth using an ellipsoid or a geoid. Many countries have created coordinate-grids customized to lessen error in their area of the earth.
Errors and accuracy
A basic tenet of surveying is that no measurement is perfect, and that there will always be a small amount of error.[13] There are three classes of survey errors:
Gross errors or blunders: Errors made by the surveyor during the survey. Upsetting the instrument, misaiming a target, or writing down a wrong measurement are all gross errors. A large gross error may reduce the accuracy to an unacceptable level. Therefore, surveyors use redundant measurements and independent checks to detect these errors early in the survey.
Systematic: Errors that follow a consistent pattern. Examples include effects of temperature on a chain or EDM measurement, or a poorly adjusted spirit-level causing a tilted instrument or target pole. Systematic errors that have known effects can be compensated or corrected.
Random: Random errors are small unavoidable fluctuations. They are caused by imperfections in measuring equipment, eyesight, and conditions. They can be minimized by redundancy of measurement and avoiding unstable conditions. Random errors tend to cancel each other out, but checks must be made to ensure they are not propagating from one measurement to the next.
Surveyors avoid these errors by calibrating their equipment, using consistent methods, and by good design of their reference network. Repeated measurements can be averaged and any outlier measurements discarded. Independent checks like measuring a point from two or more locations or using two different methods are used. Errors can be detected by comparing the results of the two measurements.
Once the surveyor has calculated the level of the errors in his or her work, it is adjusted. This is the process of distributing the error between all measurements. Each observation is weighted according to how much of the total error it is likely to have caused and part of that error is allocated to it in a proportional way. The most common methods of adjustment are the Bowditch method, also known as the compass rule, and the principle of least squares method.
The surveyor must be able to distinguish between accuracy and precision. In the United States, surveyors and civil engineers use units of feet wherein a survey foot breaks down into 10ths and 100ths. Many deed descriptions containing distances are often expressed using these units (125.25ft). On the subject of accuracy, surveyors are often held to a standard of one one-hundredth of a foot; about 1/8inch. Calculation and mapping tolerances are much smaller wherein achieving near-perfect closures are desired. Though tolerances will vary from project to project, in the field and day to day usage beyond a 100th of a foot is often impractical.
Types of surveys

Local organisations or regulatory bodies class specializations of surveying in different ways. Broad groups are:
As-built survey: a survey that documents the location of recently constructed elements of a construction project. As-built surveys are done for record, completion evaluation and payment purposes. An as-built survey is also known as a 'works as executed survey'. As built surveys are often presented in red or redline and laid over existing plans for comparison with design information.
Cadastral or boundary surveying: a survey that establishes or re-establishes boundaries of a parcel using a legal description. It involves the setting or restoration of monuments or markers at the corners or along the lines of the parcel. These take the form of iron rods, pipes, or concrete monuments in the ground, or nails set in concrete or asphalt. The ALTA/ACSM Land Title Survey is a standard proposed by the American Land Title Association and the American Congress on Surveying and Mapping. It incorporates elements of the boundary survey, mortgage survey, and topographic survey.
Control surveying: Control surveys establish reference points to use as starting positions for future surveys. Most other forms of surveying will contain elements of control surveying.
Construction surveying
Deformation survey: a survey to determine if a structure or object is changing shape or moving. First the positions of points on an object are found. A period of time is allowed to pass and the positions are then re-measured and calculated. Then a comparison between the two sets of positions is made.
Dimensional control survey: This is a type of survey conducted in or on a non-level surface. Common in the oil and gas industry to replace old or damaged pipes on a like-for-like basis, the advantage of dimensional control survey is that the instrument used to conduct the survey does not need to be level. This is useful in the off-shore industry, as not all platforms are fixed and are thus subject to movement.
Engineering surveying: topographic, layout, and as-built surveys associated with engineering design. They often need geodetic computations beyond normal civil engineering practice.
Foundation survey: a survey done to collect the positional data on a foundation that has been poured and is cured. This is done to ensure that the foundation was constructed in the location, and at the elevation, authorized in the plot plan, site plan, or subdivision plan.
Hydrographic survey: a survey conducted with the purpose of mapping the shoreline and bed of a body of water. Used for navigation, engineering, or resource management purposes.
Leveling: either finds the elevation of a given point or establish a point at a given elevation.
LOMA survey: Survey to change base flood line, removing property from a SFHA special flood hazard area.
Measured survey: a building survey to produce plans of the building. such a survey may be conducted before renovation works, for commercial purpose, or at end of the construction process.
Mining surveying: Mining surveying includes directing the digging of mine shafts and galleries and the calculation of volume of rock. It uses specialised techniques due to the restraints to survey geometry such as vertical shafts and narrow passages.
Mortgage survey:  A mortgage survey or physical survey is a simple survey that delineates land boundaries and building locations. It checks for encroachment, building setback restrictions and shows nearby flood zones. In many places a mortgage survey is a precondition for a mortgage loan.
Photographic control survey: A survey that creates reference marks visible from the air to allow aerial photographs to be rectified.
Stakeout, layout or setout: an element of many other surveys where the calculated or proposed position of an object is marked on the ground. This can be temporary or permanent. This is an important component of engineering and cadastral surveying.
Structural survey: a detailed inspection to report upon the physical condition and structural stability of a building or structure. It highlights any work needed to maintain it in good repair.
Subdivision: A boundary survey that splits a property into two or more smaller properties.
Topographic survey: a survey that measures the elevation of points on a particular piece of land, and presents them as contour lines on a plot.
Plane and geodetic surveying
Based on the considerations and true shape of the earth, surveying is broadly classified into two types.
Plane surveying assumes the earth is flat. Curvature and spheroidal shape of the earth is neglected. In this type of surveying all triangles formed by joining survey lines are considered as plane triangles. It is employed for small survey works where errors due to the earth's shape are too small to matter.[14]
In geodetic surveying the curvature of the earth is taken into account while calculating reduced levels, angles, bearings and distances. This type of surveying is usually employed for large survey works. Survey works up to 100 square miles (260 square kilometers ) are treated as plane and beyond that are treated as geodetic.[15] In geodetic surveying necessary corrections are applied to reduced levels, bearings and other observations.[16]
Profession

The basic principles of surveying have changed little over the ages, but the tools used by surveyors have evolved. Engineering, especially civil engineering, often needs surveyors.
Surveyors help determine the placement of roads, railways, reservoirs, dams, pipelines, retaining walls, bridges, and buildings. They establish the boundaries of legal descriptions and political divisions. They also provide advice and data for geographical information systems (GIS) that record land features and boundaries.
Surveyors must have a thorough knowledge of algebra, basic calculus, geometry, and trigonometry. They must also know the laws that deal with surveys, real property, and contracts.
Most jurisdictions recognize three different levels of qualification:
Survey assistants or chainmen are usually unskilled workers who help the surveyor. They place target reflectors, find old reference marks, and mark points on the ground. The term 'chainman' derives from past use of measuring chains. An assistant would move the far end of the chain under the surveyor's direction.
Survey technicians  often operate survey instruments, run surveys in the field, do survey calculations, or draft plans. A technician usually has no legal authority and cannot certify his work. Not all technicians are qualified, but qualifications at the certificate or diploma level are available.
Licensed, registered, or chartered surveyors usually hold a degree or higher qualification. They are often required to pass further exams to join a professional association or to gain certifying status. Surveyors are responsible for planning and management of surveys. They have to ensure that their surveys, or surveys performed under their supervision, meet the legal standards. Many principals of surveying firms hold this status.
Licensing
Licensing requirements vary with jurisdiction, and are commonly consistent within national borders. Prospective surveyors usually have to receive a degree in surveying, followed by a detailed examination of their knowledge of surveying law and principles specific to the region they wish to practice in, and undergo a period of on-the-job training or portfolio building before they are awarded a license to practise. Licensed surveyors usually receive a post nominal, which varies depending on where they qualified. The system has replaced older apprenticeship systems.
A licensed land surveyor is generally required to sign and seal all plans. The state dictates the format, showing their name and registration number.
In many jurisdictions, surveyors must mark their registration number on survey monuments when setting boundary corners. Monuments take the form of capped iron rods, concrete monuments, or nails with washers.
Surveying institutions

Most countries' governments regulate at least some forms of surveying. Their survey agencies establish regulations and standards. Standards control accuracy, surveying credentials, monumentation of boundaries and maintenance of geodetic networks. Many nations devolve this authority to regional entities or states/provinces. Cadastral surveys tend to be the most regulated because of the permanence of the work. Lot boundaries established by cadastral surveys may stand for hundreds of years without modification.
Most jurisdictions also have a form of professional institution representing local surveyors. These institutes often endorse or license potential surveyors, as well as set and enforce ethical standards. The largest institution is the International Federation of Surveyors (Abbreviated FIG, for French: Fédération Internationale des Géomètres). They represent the survey industry worldwide.
Building surveying

Most English-speaking countries consider building surveying a distinct profession. They have their own professional associations and licensing requirements. Building surveyors focus on investigating the condition of buildings as well as legal compliance work.
Cadastral surveying
One of the primary roles of the land surveyor is to determine the boundary of real property on the ground. The surveyor must determine where the adjoining landowners wish to put the boundary. The boundary is established in legal documents and plans prepared by attorneys, engineers, and land surveyors. The surveyor then puts monuments on the corners of the new boundary. They might also find or resurvey the corners of the property monumented by prior surveys.
Cadastral land surveyors are licensed by governments.
The cadastral survey branch of the Bureau of Land Management (BLM) conducts most cadastral surveys in the United States.[17] They consult with Forest Service, National Park Service, Army Corps of Engineers, Bureau of Indian Affairs, Fish and Wildlife Service, Bureau of Reclamation, and others. The BLM used to be known as the General Land Office (GLO).
In states organized per the Public Land Survey System (PLSS), surveyors must carry out BLM cadastral surveys under that system.
Cadastral surveyors often have to work around changes to the earth that obliterate or damage boundary monuments. When this happens, they must consider evidence that is not recorded on the title deed. This is known as extrinsic evidence.[18]
Noteworthy surveyors
Three of the four U.S. Presidents on Mount Rushmore were land surveyors. George Washington, Thomas Jefferson, and Abraham Lincoln surveyed colonial or frontier territories prior to serving office.
David T. Abercrombie practiced land surveying before starting an outfitter store of excursion goods. The business would later turn into Abercrombie & Fitch lifestyle clothing store.
Percy Harrison Fawcett is a British surveyor that explored the jungles of South America attempting to find the Lost City of Z. His biography and expeditions were recounted in the book The Lost City of Z and were later adapted on film screen.
Inō Tadataka produced the first map of Japan using modern surveying techniques starting in 1800, at the age of 55.
See also

Cartography
Chartered Surveyor
International Federation of Surveyors
Prismatic compass (surveying)
Surveying in early America
Exsecant
Royal Institution of Chartered Surveyors

Further reading
Library resources about
 Main Page

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Keay J (2000), The Great Arc: The Dramatic Tale of How India was Mapped and Everest was Named, Harper Collins, 182pp, ISBN0-00-653123-7.
Pugh J C (1975), Surveying for Field Scientists, Methuen, 230pp, ISBN0-416-07530-4
Genovese I (2005), Definitions of Surveying and Associated Terms, ACSM, 314pp, ISBN0-9765991-0-4.

Public Land Survey System Foundation (2009) Manual of Surveying Instructions For the Survey of the Public Lands of the United States.

: Association de géometres pour aide au développement. NGO Surveyors without borders (in French)
 Community forum for Land Surveyors and Geomatics Professionals offering peer-to-peer support, education, networking and tales from the field.
 The Home of the National Museum of Surveying in Springfield, Illinois
 Global social support network featuring surveyor forums, instructional videos, industry news and support groups based on geolocation.
 Good overview of surveying with references to construction surveys, cadastral surveys, photogrammetry surveys, mining surveys, hydrographic surveys, route surveys, control surveys and topographic surveys

 The History of Surveying And Survey Equipment
 National Council of Examiners for Engineering and Surveying (NCEES)
 National Society of Professional Surveyors (NSPS)
 Using Ground Penetrating Radar for Land Surveying
 Global event and community of land surveyors.

What do you call a person who conducts surveys?