[Proj] Conic projection, but centric (gnomonic)

[Andre Joost]

Am 10.11.2017 um 15:07 schrieb Lukasz Komsta:
> Dear Steve,
>
>> Lukasz, if you are trying to transform from this projection to wgs84 or GPS,
>> you will need to add a +towgs84 or +nadgrids component. I think developing a
>> nadgrids gridshift file to accompany this would be the best solution, since
>
> Thank you, in my version of cs2cs (and also online calculators), adding
> towgs84 would change the result (but increasing error), whereas adding
> nadgrids does not change anything at all (it seems that ellps=sphere
> forces this behavior).
>

+nadgrids expects a gridf shift file which you have to create on your 
own. It shifts the unprojected coordinates (i.e. degrees), regardless of 
the projection. I doubt this is of any use for you.

HTH,
André Joost