[Proj] Azimuthal Equidistant question

[support.mn at elisanet.fi]

Hello,

without going any deep in your question ..

if you are far away from what is expected
you might need some additional parameters
to the projection setup... either lat_0, lon_0 needs
some initialization value or x_0 or y_0 is
missing something.. or some other parameter
with that projection .. if that does not help then
the projection might be wrong... etc. etc..

regards: Janne.

-------------------------------------------------------------

Joseph White [JWhite at terragotech.com] kirjoitti: 
> Hi, all,
> 
> I'm trying to track down an issue I'm seeing with Azimuthal Equidistant
> values when compared to ESRI.  The ESRI coordinate system I'm using is
> World Azimuthal Equidistant.  I'm using some sample data that is in the
> Tucson AZ area.
> 
>  
> 
> The coordinate strings we're passing into PROJ to set up the transform
> are:
> 
> Src: +proj=aeqd +lat_0=0 +lon_0=0  +x_0=0 +y_0=0 +datum=WGS84 +units=m
> +no_defs
> 
> Dest: +proj=longlat +datum=WGS84 +no_defs
> 
>  
> 
> I pass in the following coordinates (Easting,Northing):
> 
> 1.        -9939304, 6673447
> 
> 2.       -9930938, 6684888
> 
>  
> 
> I get this result:
> 
> 1.        -69d 0' 0.12", 32d 15' 14.159"
> 
> 2.       -68d 59' 24.215", 32d 19' 5.934"
> 
> Needless to say, this isn't anywhere near Tucson, and is about 31-32
> degrees off longitudinally.
> 
>  
> 
> When I try using a sphere (I've tried both semi major axis and
> equal-area), the values are much closer, but still off.  
> 
> Src: +proj=aeqd +lat_0=0 +lon_0=0  +x_0=0 +y_0=0 +a=6378137.0
> +b=6378137.0 +units=m +no_defs
> 
> Dest: +proj=longlat +a=6378137.0 +b=6378137.0 +no_defs
> 
>  
> 
> 1.        -110d 50' 50.416", 32d 6' 24.361"
> 
> 2.       -110d 51' 24.032", 32d 10' 15.985"
> 
>  
> 
> Src: +proj=aeqd +lat_0=0 +lon_0=0  +x_0=0 +y_0=0 +a=6371007.1809
> +b=6371007.1809 +units=m +no_defs
> 
> Dest: +proj=longlat +a=6371007.1809 +b=6371007.1809 +no_defs
> 
>  
> 
> 1.        -110d 59' 11.622", 32d 4' 58.135"
> 
> 2.       -110d 59' 45.523", 32d' 8' 49.575"
> 
>  
> 
> Does anyone out there have any idea why this is happening?  I'm at my
> wits end to explain it.
> 
>  
> 
> Thanks
> 
>  
> 
> Joe White
> 
>  
> 
>  
> 
> 
> _______________________________________________
> Proj mailing list
> Proj at lists.maptools.org
> http://lists.maptools.org/mailman/listinfo/proj