Meter per pixel

[pusia1]

Hello.
Can I get meters per pixel with latitude and screen distance?

[gwaldron]

One approach is to pick two points that are one meter apart and convert them both into window coordinates.

• Take you lat/long point and convert it to ECEF coordinates (meters).
• Transform that point into window coordinates (pixels) by multiplying it by (view matrix * projection matrix * window matrix).
• Pick a second point 1 meter away from the first point and repeat.
• The distance between the 2 points in window coordinates is the number pixels per meter.
• Invert that and you have meters/pixel, more or less.

You can also refer to the algorithm in OSG that calculates an approximate pixel size for a bounding sphere:
https://github.com/openscenegraph/OpenSceneGraph/blob/master/include/osg/CullingSet#L174

Good luck.