[Proj] Changing Radius of the Earth?
Jose Gonçalves
jagoncal at gmail.com
Tue Apr 10 09:14:23 PDT 2012
For Mars use its ellipsoid axis: +a=3396200 +b=3376189
or the mean sphere: +R=3389508
Data from http://www.hnsky.org/iau-iag.htm
Regards
José Gonçalves
Em 10 de abril de 2012 16:16, Fischer, Robert P. (GISS-6110)[COLUMBIA
UNIVERSITY] <robert.p.fischer-1 at nasa.gov> escreveu:
> How do I change the radius of the (spherical) Earth in proj.4? I'm using
> the proj.4 string:
>
> " +proj=laea +lon_0=-40.000000 +lat_0=74.000000 +x_0=1000000
> +y_0=1700000 +ellps=sphere"
>
> ..and have discovered that proj.4 assumes a radius of exactly 6370997m
> (from pj_ellps.c):
>
> "sphere", "a=6370997.0", "b=6370997.0", "Normal Sphere (r=6370997)",
>
> We are running code on a spherical Earth, with a radius (slightly)
> different from that above. For consistency sake, proj.4 will need to use
> the same Earth radius as the code that calls it. How do I set up a
> projection on a spherical Earth with a custom radius?
>
> Also... if someone wanted to use proj.4 for mapping on Mars, how would
> they do that?
>
> Thanks,
> -- Bob
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