[GRASSLIST:4913] Re: Problems with importing polar data

Glynn Clements glynn.clements at virgin.net
Fri Nov 8 21:53:57 EST 2002

Anton B. Ivanov wrote:

>   I am new to the GRASS program and it seems to be VERY powerful. However,
> I have been a little frustrated trying to import my polar data into it. 
>   Here's a problem : I have data (images) projected into a polar
> stereographic projection (using some camera speicific software). I import
> them using r.in.bin and set up proper lat/lon bounds for these images. The
> projection setup is as ups (see PROJ_INFO file below). 
>   However, when I'm trying display data, put a grid on it or make a
> postscript map, the output projection look like a simple cylindrical or
> latititude/longitude. 

Is the data which you imported really in UPS, and not Lat/Lon?

>   How do I tell GRASS to display my data in polar stereographic projection
> and overlay grid on it?

GRASS displays data "as is"; none of the display commands will attempt
to project it. The *only* commands which project data are r.proj,
v.proj and s.proj. Most of the other commands simply work with
arbitrary X/Y coordinates, without any consideration as to what those
coordinates actually represent (apart from a few commands which take
account of the units, e.g. feet/metres).

>   Another problem is to project data from simple cylindrical projection
> into polar stereographic (using r.proj) . I have no luck there either. 

If you have Lat/Lon data, import it into a Lat/Lon location. Then
create a UPS location, and run r.proj from that location.

>   Any help will be highly appereciated!!!!
>   Thanks a lot in advance
>   Anton Ivanov
> PS. here's PROJ_INFO and PROJ_UNITS pair for my location. I work with
> Martian data, so geoid is that of Mars and no datum has been specified.  
>  ---------------------------------- 
> name: Universal Polar Stereographic 
> proj: ups 

Again, is the data which you are importing really in UPS? The GRASS
import utilities don't perform any projection of the data; you have to
import it into a location whose projection matches the data.

Glynn Clements <glynn.clements at virgin.net>

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