[Proj] Difference in Orthographic projection between Proj4 and Global Mapper

[Kristian Evers]

No, it is the same as using +ellps=sphere – as was already tried. By doing a bit of manual bisection on the radius I came up with the following that more or less matches the results from GM:

> echo -3.1 52.1 | proj +proj=ortho +lat_0=52 +lon_0=-3 +a=6367440 +units=m +no_defs
-6826.72        11117.97

I have no idea if that works for other coordinates though! Probably not…

Kristian

Fra: proj-bounces at lists.maptools.org [mailto:proj-bounces at lists.maptools.org] På vegne af Thomas Knudsen
Sendt: 7. juli 2016 11:32
Til: PROJ.4 and general Projections Discussions
Emne: Re: [Proj] Difference in Orthographic projection between Proj4 and Global Mapper

Does this solve the problem? (taking the radius from the remotesensing page you referred to):

$ echo -3.1 52.1 | proj +proj=ortho +lat_0=52 +lon_0=-3 +x_0=0 +y_0=0 +a=6370997 +f=0 +units=m +no_defs

Output:

-6830.53        11124.18

/Thomas
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