QuoVadis 6 works with a wide range of various map types:
With scanned raster maps and other bitmaps, e.g. internet downloads, it is essential that they can be georeferenced. For map calibration the following requirements must be fulfilled:
You will find an overview on the maps in our webshop at http://shop.quovadis-gps.com
In cartography, there are two basic map types which have fundamental technical differences: Raster and Vector maps.
These differences do not only apply to the techniques applied but also to the map design and the appearence in the map window.
While raster maps can be interprated as a type of digital photo, a vector map is more a mathematical term.
In other words: A raster maps consists of single pixels, each representing a given place on earth (coordinates) and haveing a clearly defined color and brightness. However, the software cannot know what kind of structure a given pixel represents. Thus, the software cannot define if a red pixel is part of a symbol, a label, a line or even a road of a certain class. Therefore it is not possible to implement any kind of routing functionality with a raster map. Another disadvantage of a raster map is that the image quality is strongyl influenced by the zoom factor. When viewing a ratser map at 100% zoom level, the image quality is optimal. Zooming in above this point will not improve the degree of details, the map image will only become “rusterized”. On the other hand, when zooming out, all details will be scalled down in a linear way. So when zooming out, you wont be able to read any kind of labels pretty soon. Thus, it is usually difficult to orientate in a raster map at small zoom scales, e.g. in cases where you need a good overv.
There are also substantial benefits of raster maps:
1) You get high quality raster maps for almost any part of the earth in varoius scales. You can even scan and georeference your own raster map and thus produce your “own” digital map.
2) High quality raster maps usually have a very realistic map design which gives a good impression on landscape characterstics and relief energy. Therefore, raster maps are suited much better for trip planning than vector maps, except if yiou are interested in the fastest or quickest route.
Below you find a typical example of a raster map at three different zoom levels:
Raster maps might be classified into 3 types:
These include general bitmap formats like PNG, JPG, BMP, etc. Such formats are generated when scanning paper maps. Such bitmaps files have to be calibrated in QV manually in order to use them as a map.
Remark: Standard raster maps must always be loaded into the PC's RAM as a whole. Thus, depending on your hardware specification, the maximum map size will be limited. So, the more RAM you have installed to your PC the better. In this context, raster maps in the TIF format make an exception: QV can also load them in parts.
Some special raster formats have been developed which include the calibration information in the file:
BSB (KAP), GeoGrid, GeoTIFF, etc. During import, these maps are automatically georeferenced in QV.
Raster maps always encounter the problem that the image quality will vary with the zoom scale. Some optimized raster formats are available which compensate for this loss in quality by implementing different zoom scales in a preprocessed inscription to the file format. The performance and quality during zooming is remarkably increased.
These optimised geo-raster formats include: SID, ECW, BAYO and the proprietary QV format QBR.
Raster maps in one of these formats offer optimum performance and are usually calibrated and ready for use.
In contrast to that, Vector Maps consist of pure point coordinates and a specification on what element the point coordinate belongs to and how it should be plotted. Such a point might be just the center of a settlemet, a mountain peak or a part of a river, railway or road. In terms of roads, the huge benefit is that the road can be calssified according to road category (highway, interstate, country road, track, etc.) and the topology of the whole road network is stored. So vector maps are an essential requirement for routing functionalities: Usiually they provide a database which allow for adress queries. Another advantage of vector maps is that, according to theit internal structure, the degree of detail can be adapted to the zooml level. For example you can eliminate roads of lower categrories when zooming out. Thus you always have a good overview when zooming in vector maps. The design of a vector map in the map window is defined by a rendering process. For this purpose, various point, line and label styles are attributed to the corresponding structures and polygones like forests will be filled with a defined pattern. However the internal structur of such a polygone is always homogenous, so no internal differenciation can be recognized.
Of course ther also some drwabacks of vector maps:
1) It is a very huge effort to produce them, so they are only available for areas with a high commercial value.
2) They are always concentrated on specific topics like roads. Concerning other topics, their usability is typically very limited. Exampel: if you are off the road network in a street map, you are in the middle of nowhere and won't find valuable information for orientation.
3) Usually, the map design is relatively poor and does not deliver anything like landscape characteristics. Although this has greatly improved with some latest-generation topomaps, even such high-quality vector maps cannot compete with high quality raster maps in terms of degree of detail and plasticity.
4) Vector maps are always compiled for a specific software product. So they can only be used on the platform for ehich they have been optimized.
Below you find a typical example of a vector map at two different scales:
A careful calibration assumed, QQV will give you more accurate coordinates than you would be able to extract from a map by other means. However note, that the following factors will influence accuracy:
The earth is not a perfect sphere but an ellipsoid, and even this is not symmetric.
In contrast to this, latitudes and longitudes refer to symmetric mathematically defined circles which are evenly distributed over the sphere. However, the earth's radius is not a constant but varies for different places on earth.
To cope with this problem, a radius will be defined when creating a map which fits best to a specific geographic area. And, as the surface of the earth is a spheroid, 2 different radii (semi-major and semi-minor axes) have to be considered.
The map reference system or map datum defines a specific set of earth radii and thus to a specific ellipsoid.
On the basis of this ellipsoid, a map will be created. Also a GPS receiver has to refer to a specific ellipsoid in order to calculate a position. Several map reference systems with their specific advantages and disadvantages are in use, not only for different geographic areas but also within the same country.
As a direct consequence, the coordinates of two maps which cover the same region and which are compiled with different map reference systems, the same point will have different coordinates.
Or, if you switch your GPS unit to another map datum, the coordinates will change although your location is exactly the same.
Therefore, if you want to specify your position with a GPS receiver in a map, you have to know the map reference system and configure your GPS unit accordingly.
Meanwhile, the map reference system WGS 84 has been widely accepted as a global, international standard but there are many maps which refer to another map datum. In general, local maps will not refer to WGS 84.
QV will facilitate all the troubles encountered with different map reference systems a lot.
As all GPS units and QV will work internally based on WGS 84, you do not need to convert your GPS unit but retain the basic WGS 84 settings, regardless of the map datum being used in a QV map. The required coordinate conversion will be handled by QV together with your GPS unit.
When calibrating your scanned map, you should enter the map datum whenever available (unfortunately it is not often the case).
Then, when you save coordinates in QV and transfer them to the GPS unit, QV will automatically convert them to WGS 84.
And if you extract coordinates from your map, they will also be automatically converted to the map reference system which you have currently set.
If the datum is not specified on your map, it is often worth asking the map manufacturer. The accuracy of QV may remarkably increase by setting the adequate map datum! Most map publishers will give you this information.
German maps are usually based on the Potsdam map datum, French IGN maps on New French triangulation.
If you save waypoints in the QV map display, the necessary conversions are performed automatically. When manually entering waypoint coordinates, you can select the map datum to which the coordinates refer in the dialog input box.