[GRASS-dev] latlon support

[Hamish]

Glynn Clements wrote:
> AFAICT, the most important case to solve is when the region is set to
> the Bering strait, and a vector map has Alaska at ~180W and Sibera at
> ~180E. Some of the data will need a 360-degree shift to obtain the
> correct relative position.


the same problem applies to data which is not land based!
fwiw, my longitude >170 and in my oceanography work I wrap past 180 on
a fairly regular basis. (~90% is raster for me, certainly others work
with point data, ship tracks, 200nm buffer zones, and sonar swaths)


I fully understand that it is a total pain in the neck to program the
longitude wrap-around successfully, but to the end users who have to
deal with it it's a real godsend and a real draw-card for GRASS. Not
much other GIS software can do it nearly as well as GRASS 5/6's raster
map libs, Xmonitors, d.zoom, etc. And so I would argue it is well worth
the (albeit large) effort to keep the libraries wrapping. The current
raster map code works remarkably well for most tasks.


see also the earlier bug reports for lat/lon wrap support for the vector
libs and r.resamp.(?? whatever one Glynn was fighting with some months
ago which exposed the neighbors' complication).


Markus Metz wrote:
> Restrict both raster and vector maps to the 180 degree lon

note that the planetary science people prefer to keep lon as 0-360,
not -180 thru 180. (search ML archives for "Mars")


Also, AFAIR, for vector maps d.what.vect report correct land areas for
lat/lon polygons. So the vector lib isn't completely lat/lon braindead.


Hamish