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I am trying to create a geotiff and the software (raster design) is asking for a code that I thought was EPSG code. however while trying to find out what epsg = us48 I noticed that the dialog actually says geotiff code. Now I am really in a loop. autocad map contains a coordinate system that is named us48 albers equal area, nad 27 meter orig lat 23, orig long -96, northern standard par 45.5, southern standerd par 29.5 ESRI difines the same system as...

'PROJCS["USA_Contiguous_Albers_Equal_Area_Conic_USGS_version",GEOGCS["GCS_North_American_1983",DATUM["D_North_American_1983",SPHEROID["GRS_1980",6378137.0,298.257222101]],PRIMEM["Greenwich",0.0],UNIT["Degree",0.017453292519943295]],PROJECTION["Albers"],PARAMETER["False_Easting",0.0],PARAMETER["False_Northing",0.0],PARAMETER["Central_Meridian",-96.0],PARAMETER["Standard_Parallel_1",29.5],PARAMETER["Standard_Parallel_2",45.5],PARAMETER["Latitude_Of_Origin",23.0],UNIT["Meter",1.0]]'>

and it says USGS after it. This is the same as EPSG 6703, I cannot find anything that matches in the raster design code. I found USA US National Atlas Equal Area but it is lambert azimuthal 45, -100 the code for it in raster design is 2163 Apparently the autodesk version is supposed to be the same as epsg as desribed in this document... http://svn.osgeo.org/fdo/trunk/Providers/GenericRdbms/com/ExtendedCoordSys.txt/

The values in this document are what I am using in the raster design dialog that I thought were epsg. Can someone straighten me out? I want an epsg code for US48

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3 Answers

up vote 2 down vote accepted

Pasting your code in to http://prj2epsg.org gives an EPSG code of 5070 http://prj2epsg.org/epsg/5070

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So you have two different sources, ESRI and Autocad, with very different definitions of what "us48" means. You definitely don't want to mix NAD27 and NAD83, there are significant differences between them and data from mixed sources will not line up. Basically you have to throw out the name "us48" and work backwards from the parameters and find the matching EPSG from those. SpatialReference.org is your friend here.

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My solution was pretty simple. I was able to export the geotiff with no projection. When I added it to a project with the correct crs in arcmap it came in at the right place. So then I used the georeferencing tool and updated the georeferencing. quick and dirty. It got me what I needed.

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