[GRASS5] Re: [GRASSLIST:8031] Re: Oblique Mercator Projection in GRASS

Paul Kelly paul-grass at stjohnspoint.co.uk
Wed Aug 24 09:12:17 EDT 2005

Hello Morten

On Wed, 24 Aug 2005, Morten Hulden wrote:

> I just tested an omerc_michigan PROJ_INFO file with the alternative 
> projection parameters and it does not work - the alpha: key-value pair 
> mysteriously disappers somewhere in the subroutines that construct the proj 
> command.
> As a matter of fact /any/ key-value pair in the PROJ_INFO file starting with 
> either "a" or "f" will fail to show up in the constructed proj commmand, 
> except "a:" and "f: of course". Could this have something to do with the 
> routines extracting ellipse parameters? Like discarding or not looking 
> further into the projinfo stucture if first char of a key is "a" or "f"?

Yes indeed I think you're right---and it looks like this bug has been 
there for 10-15 years!
The problem is the use of strncmp() in lib/proj/get_proj.c which only 
checks the first few characters of a string for a match--resulting in a 
matching any parameter beginning with a, etc.

I have committed a fix to CVS; please test.


> name: Oblique Mercator
> datum: nad83
> towgs84: 0.000,0.000,0.000
> proj: omerc
> ellps: grs80
> a: 6378137.0000000000
> es: 0.0066943800
> f: 298.2572221010
> lat_0: 45.3091666667
> lonc: -86.0000000000
> alpha: 337.25556
> k_0: 0.9996000000
> x_0: 2546731.496
> y_0: -4354009.816
> no_rot: defined
> no_uoff: defined
> rot_conv: defined

More information about the grass-dev mailing list