[GRASS5] Reading Projections

[Morten Hulden]

On Thu, 21 Sep 2000, Frank Warmerdam wrote:

> It seems to me that the location's default projection might be
> different than the projection of a particular raster in that location
> ... is that right?

No. Every raster or vector map in a particular location share the same
projection (described in PROJ_INFO). Maps, like regions within a grass
location, can have different borders and even different resolutions
(descrbed in WIND or DEFAULT_WIND) but they are all based on same
projection.

Whether this restriction will be necessary in the future I am not sure.
The speed of today's hardware and software may already allow 'dynamic'
projections so each region/map is projected on the fly. We could then have
a DEFAULT_PROJ_INFO for the location, and a PROJ_INFO file for each region
or map within that location, just like we have DEFAULT_WIND and WIND. This
would make it unnecessary to define several locations for the same
geographic area, which only differ in projection and save a lot of disk
space. Maybe this is something GRASS6 or later ...

Morten Hulden



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