[GIS] albers projection to Lat, Lon

cartographycoordinate systemtranslation

Thanks in advance for helping me with my issue. This GIS stuff is using parts of my brain that have remained idle since high school, and some parts are working faster than others.

I have land data stored as Albers projection and I want it converted to Lat, Lon so I can display it on Bing maps. The prj.adf file in the folder containing my data is this:

Projection    ALBERS    
Datum         NAD83    
Spheroid      GRS80    
Units         METERS    
Zunits        NO    
Xshift        0.0       
Yshift        0.0

Parameters    
  29 30  0.0 /* 1st standard parallel    
  45 30  0.0 /* 2nd standard parallel    
 -96  0  0.0 /* central meridian    
  23  0  0.0 /* latitude of projection's origin    
  0.0 /* false easting (meters)    
  0.0 /* false northing (meters)

I have been searching the web for said transformations, and have come close with the article by James Murtha (http://www.delphi3000.com/articles/article_4479.asp), but this apparently maps Lat Lon to his 1000 scale map, which is not the same scale as my data. The units described in my prj file show "Meters" – so do I need to calculate the number of meters between the 1st and 2nd standard parallel and assume that this is my unit size in the y direction?

Does anyone have any formulas (or links to information) that I can apply to map between (Lat, Lon) and the Albers (X,Y) projections? Sorry, but I do not have ARCGIS or any other tools to help me so I have to do this in native code without the conversion libraries in these tools.

Thanks – Steve Tufty

Best Answer

You can use the Proj.4 library to convert coordinates from one projection to another. (However Proj.4 will not read your dataset - that is up to you) If you can't link to the library, then a stroll through the source code might get you the formula you are looking for.

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