[GRASSLIST:9687] Re: This is NOT ARCINFO :) r.proj - OK - thx Markus, Ian

[Glynn Clements]

Robert Kuszinger wrote:

> yes, g.region affects all operations, and not only on the source -
> logical :) !!!

As a general rule:

1. Raster output maps have their bounds and resolution equal to those
of the current region.

2. Raster input maps are automatically cropped/padded and rescaled
(using nearest-neighbour resampling) to match the current region.

There are a few exceptions to this:

r.in.* programs read the data cell-for-cell, with no resampling. When
reading non-georeferenced data, the imported map will usually have its
lower-left corner at (0,0) in the location's coordinate system; you
need to use r.region to "place" the imported map.

Some programs which need to perform specific types of resampling (e.g. 
r.resamp.rst) read the input maps at their original resolution then do
the resampling themselves.

r.proj has to deal with two regions (source and destination)
simultaneously; both will have an impact upon the final result.

-- 
Glynn Clements <glynn at gclements.plus.com>