All map elements require at least one <point> element which defines a geographical position on the map. In general a geographical point is defined as a latitude/longitude pair. If cartesian X/Y attribute values are used, the point is calculated using the <origin> given in the FIR configuration file (config.fir).
Cartesian coordinates are also used when defining symbols in symbols.xml where the final position of the symbol will be the Cartesian origin point.
When a map is loaded all points defined as a latitude/longitude pair are transformed to cartesian X/Y values relative to the system origin point and stored as such internally. So using cartesian X/Y might slightly improve startup speed but keep in mind that in that case the system origin point cannot be changed.
The Cartesian X or Y value is defined as a float in Nautical miles.
<point x="124.35" y="-20.565" /> <point x="-0.601415" y="-0.132565" /> <point x="0.601393" y="-0.133375" />