[Proj] Lambert Azimuthal Equal Area scale

Charles Karney charles.karney at sri.com
Thu Jun 11 07:34:48 PDT 2015


Evidently the 4.8.x version of geod is inaccurate.  I'm surprised...  I
didn't know it was quite this bad on relatively short lines.

The 4.9.x version of geod gives the right answer.

On 06/11/15 10:22, Lourens Veen wrote:
> On 10/06/15 17:41, Lourens Veen wrote:
>> I'll check everything again tomorrow, this time with lon and lat in the
>> right order for invgeod to understand it correctly. I agree that geod
>> should be fixed, both geod and proj are libproj utilities, they should
>> correctly interpret each other's default output format.
>
> Well, I reversed lat and lon, and I'm getting much more reasonable
> results now. I'm still getting a discrepancy between GeographicLib and
> proj though:
>
> proj 4.8.0:	(Ubuntu package)
>
> $ invgeod +ellps=WGS84 +units=m
> 43.948780899203733 -153.87240094587023 44.036369120054417
> -153.93214592316059
> -26d7'4.466"	153d50'26.145"	10861.026
>
> GeographicLib-1.42	(from source)
> $ GeodSolve -i
> 43.948780899203733 -153.87240094587023 44.036369120054417
> -153.93214592316059
> -26.19689664 -26.23839343 10848.141
>
> For my purposes, a 15m difference is not such a problem, but I'd like to
> be sure that this is a precision issue, rather than a mistake on my part
> somewhere. Perhaps this is why there's a new backend in 4.9.0?
>
> Thanks,
>
> Lourens
>



More information about the Proj mailing list