[GRASSLIST:3449] Re: defining default region for importing data

[Roger Miller]

On Thursday 04 April 2002 19:52, Bill Rising wrote:

> Then... the dialog comes up for the default region, and I haven't a clue
> what to specify. Where would I look to find this information?

You may be making this more difficult then it needs to be.  Normally the 
values you use to define the default region are the extents of the region 
you're concerned with; the largest easting for the east, the smallest easting 
for the west, the largest northing for the north and the smallest northing 
for the south.  The resolution needs to be set to a reasonably small fraction 
of the N-S and E-W dimension, say about 1/1000th or so.

It isn't always convenient to know those values ahead of time.  In that case 
you can set the; values to arbitrarily high or low values.  In some cases 
I've just set west and south to 0  and east and north to 1.

That said, it is important to realize that the area displayed on the GRASS 
monitor is defined by the current region and at the outset that region is set 
to the default region.  If you then display something that is either outside 
the current region or much, much smaller then the current region then you may 
not see anything at all.

When you first display something you can  get around the problem of not 
knowing what the correct region is by setting your current region to the 
region covered by the map your trying to display.  If you display a raster 
map then the command is

g.region rast=<file name>

for a vector file it would be

g.region vect=<file name>

and for a sites file it would be

g.region sites=<file name>

It is good to have a reasonable default region, but not necessary.  You can 
set the default region after you find out what you want the region to be.


Roger Miller