 geo_point field does not support GeoJson which can be a PITA if your data is in such a format. Indexing it as a geo_shape is an option but very wasteful.
server/src/main/java/org/elasticsearch/common/geo/GeoUtils.java
public static final double MAX_LAT = 90.0;
    
    public static final double MIN_LAT = -90.0;
    
    public static final double MAX_LON = 180.0;
    
    public static final double MIN_LON = -180.0;
    public static final String LATITUDE = "lat";
    public static final String LONGITUDE = "lon";
    public static final String GEOHASH = "geohash";
    
    public static final double EARTH_SEMI_MAJOR_AXIS = 6378137.0;      
    
    public static final double EARTH_SEMI_MINOR_AXIS = 6356752.314245; 
    
    public static final double EARTH_MEAN_RADIUS = 6371008.7714D;      
    
    public static final double EARTH_AXIS_RATIO = EARTH_SEMI_MINOR_AXIS / EARTH_SEMI_MAJOR_AXIS;
    
    public static final double EARTH_EQUATOR = 2 * Math.PI * EARTH_SEMI_MAJOR_AXIS;