[Proj] Extracting the to_meter parameter from a projection
Hearne, Michael (US SSA)
michael.hearne at baesystems.com
Tue Nov 15 14:18:53 EST 2005
I'm working on a piece of software that uses proj4 as a library. I have
it working, and for the most part, understand how to get it to do what I
want. What I cannot quite figure out, however, is how to determine the
units of a given projection. I did a little digging through the source,
trying to find this, and the closest I could come to this was the
"PJconsts" struct defined in projects.h. This structure contains
parameters "to_meter" and "from_meter", which presumably are values that
one could use to convert whatever units the projected values are in to
or from meters.
I have not been able to find anything that would tell me how to
instantiate a "PJconsts" structure.
If my usage to create a projection is something like this:
inProj = pj_init(nParams,(char**)params);
then is there a function (or chain of functions) that I can call that
will get me either the units of the projection, or the "to_meter" and
I've already experimented with pj_get_def, and I get a string like this:
" +proj=utm +datum=WGS84 +ellps=WGS84 +towgs84=0,0,0"
which has no information about the units or how to convert from whatever
the units might be.
More generally, is there any documentation (a la doxygen) on the Proj4
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