Crs.MetersXY Method
Returns local conversion factors between true meters and the length unit of the projection.
MetersXY(Point point)
Returns local conversion factors between true meters and the length unit of the projection.Syntax
public Point MetersXY (
Point point
)Parameters
Return Value
Remarks
This method gives the relation between Crs coordinates and true meters near a given (projected) point, which depends on both the local scale factors and the choice of length unit in the projection. (But it does not depend on the current scale: Crs coordinates are unchanged during a zoom, unlike pixel coordinates.) The method returns an x value and a y value (as parts of a Point). To convert a short distance, parallel to the x-axis (or the y-axis) of the Crs and near the given point, to meters, you can multiply the distance (expressed in Crs coordinates) by the returned x value (or the y value).
For an oblique distance, you can use the theorem of Pythagoras, which says that the distance = sqrt(dx*dx+dy*dy), but only if the x- and y-directions are at right angles in real life (not just on the map). This is true for conformal projections, and for cylindrical projections in equatorial aspect, but not generally: it is false for the OrthographicProjection, for example. But to compute distances, it is easier to use the Length method; MetersXY is appropriate if you need the local scale factors at a given point.
With metersXY, the scale can be calculated if the ratio between presented length and length in the reference system in known.
Platforms
Windows, Linux, Android