mapserver tif projections

[Frank Warmerdam]

On 7/28/05, Douglass Davis <douglass_davis at earthlink.net> wrote:
>  
>  Hello All,
>  
>  I just got an elevation tif file (w/aux,prj, and tfw) from the seamless
> data distribution center: http://seamless.usgs.gov/.  I am still trying to
> understand projections, I read through the tutorial and user manual and
> looked through the proj4 documentation, but I am still not really sure how
> to do this.
>  
>  Now, I know it uses Lambert Azimuthal Equal Area Projection. But, how do I
> represent this projection in a map file, and pass the needed parameters into
> proj4?  
>  
>  I tried putting this in my Raster tif layer:
>  
>      PROJECTION
>        "proj=laea"
>        "lon_0=100.00w"
>        "lat_0=45.00n"
>      END
>  
>  But it didn't work.  Can some one help me with getting the correct
> parameters to put in the map file?
...
> Ellipsoid_Name: Sphere Semi-major_Axis: 6370997.0
> Denominator_of_Flattening_Ratio: 1.0 

Douglass, 

In what way did it not work? 

Try adding "ellps=sphere" to your definition.  Your current definition has
no earthmodel definition and depending on your setup there may be no
default. 

Note that most projections on a sphere don't map well to conventional
ellpisoid coordinate systems.  You may find you need to use "ellps=WGS84"
instead to get good correspondence. 

Good luck,
  
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