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As you know we have two kinds of coordinate systems in GIS : Geographic coordinate systems and projected coordinate systems
consider these situations:

  • I have a shapefile that has projected coordinate system, I mean the coordinates of the vertexes are in PCS, so there's no problem I can extract vertices with GDAL/OGR library and then show them in OpenGL with orthographic projection. since the coordinates are in meters and they're projected on a 2D plane, there will be no problem I think.

  • The datasource has a geographic coordinate system and I just want to render it in a projected coordinate system, so I have to do the transformation with PROJ.4 library and then render the transformed coordinates in OpenGL. Again I think there will be no problem, since the coordinates I want to show areb projected on a 2D plane.

  • The datasource has a geographic coordinate system and I want to render them in the the same GCS on an OpenGL window. So I extract coordinates with GDAL/OGR in geographic coordinate system and without any transformations, I'll render them in OpenGL. How can I achieve this? I mean how can I set up an ellipsoidal plane in an OpenGL window just like ArcGIS does renders data in geographic coordinate system?

Sepideh Abadpour
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  • Are you trying to display coordinates from different coordinate systems at the same time? Or just geographic coordinates? If the former, you have to project at least some of them so all coordinates are in the same SR. If the latter....why not just display it as x-y data? – Juffy Sep 17 '13 at 00:40
  • No, For the first two paragraphs I don't have any problem. In the third of course all of the layers that are going to be shown at a time are in the same geographic coordinate system, but as you know geographic coordinates are on an ellipsoid, I just want to khnow how can I make I OpenGL to show such coordinates on a flat monitor. Remember whenwver I move the mouse on the screen I want original coordinates be shown on the status bar in decimal degrees. thanks @Juffy for your paying attention – Sepideh Abadpour Sep 17 '13 at 05:23
  • " I just want to khnow how can I make I OpenGL to show such coordinates on a flat monitor." - I guess I don't see what the problem is. Either render them using decimal degrees as your x-y units as you would with a PCS (the lazy way :) ) or you'll have to project it one way or another. That's what a projection is - making a 3D surface look flat. – Juffy Sep 17 '13 at 23:56

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