[GRASS-user] geogrid not smooth in ps.map output

Moritz Lennert mlennert at club.worldonline.be
Thu Feb 11 01:45:12 PST 2016

On 08/02/16 16:48, Tyler Smith wrote:
> On Sun, Feb 7, 2016, at 05:17 PM, Markus Neteler wrote:
>> On Fri, Feb 5, 2016 at 8:08 PM, Tyler Smith <tyler at plantarum.ca> wrote:
>>> How can I plot geographic grids as smooth curves with ps.map?
>> What about using v.mkgrid and then reprojection it using vertex
>> densification as provided by v.proj?
> Thanks Markus,
> That sounds reasonable. However, based on your and Alex's comments, I
> did some digging into ps.map. It appears the resolution of grid lines is
> hardcoded to use 10 vertices across the length of each grid line, via:
>    #define SEGS 10
> in do_geogrid.c. I changed this to 100 and recompiled, and now I have
> nice smooth grids. This suggests that perhaps a permanent fix would be
> to replace the SEGS macro with an additional argument to the geogrid
> command in the ps.map instruction set. That way users could tune the
> value to suit the map they are preparing. Alternatively, some more
> sophisticated calculation could be used to determine the number of
> segments. Or it could just be set to a sufficiently high number.
> I can look into one or more of these options if it sounds generally
> useful; I don't yet understand how the ps.map arguments are parsed, but
> it looks to be within my capabilities to make the change.

Try attached diff as a starting point. Certainly needs some more 
clean-up and inclusion in the documentation in ps.map.html.

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