[GRASS-user] How to Import and Export Maps Using Grass

GRASS GRASS user
1

I am programming a flight simulator and need to create landscape imagery. I
have downloaded the New York State orthoimagery available at
http://www.nysgis.state.ny.us/gateway/mg/2006/onondaga/

I now need to combine several image tiles into one, reduce their resulting
size, etc. How can I do this with Grass? I have never used Grass, but hope
somebody could point me to some applicable tutorials or outline the major
steps.

Basically, I'd like to be able to view the imagery as a set of combined
images and then be able to output areas at specific pixel resolutions.
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2

On Sat, Jan 16, 2010 at 3:46 PM, David Benman <dave@dbenman.com> wrote:

I am programming a flight simulator and need to create landscape imagery. I
have downloaded the New York State orthoimagery available at
http://www.nysgis.state.ny.us/gateway/mg/2006/onondaga/

I now need to combine several image tiles into one,

This would be the r.patch command:
http://grass.osgeo.org/grass64/manuals/html64_user/r.patch.html

Procedure:
g.region rast=map1,map2,map3[,map4...] -p
r.patch input=map1,map2,map3[,map4...] output=hugemap

reduce their resulting size

That's r.resamp.stats - Resamples raster map layers to a coarser grid
using aggregation.
http://grass.osgeo.org/grass64/manuals/html64_user/r.resamp.stats.html

g.region res=xx
# with xx a number which is the destination pixel resolution
r.resamp.stats input=hugemap output=hugemap_lowres

Then export (e.g. GeoTIFF):
r.out.gdal input=hugemap_lowres output=hugemap_lowres.tif

, etc. How can I do this with Grass? I have never used Grass, but hope
somebody could point me to some applicable tutorials or outline the major
steps.

Hope above gives an indication. Otherwise there is material here to read:
http://grass.osgeo.org/gdp/

Markus

3

David Benman wrote:

I am programming a flight simulator and need to create
landscape imagery. I have downloaded the New York State
orthoimagery available at
http://www.nysgis.state.ny.us/gateway/mg/2006/onondaga/

(see also the now mostly defunct (mature?) terragear project at
http://terragear.org/ which supplies the SRTM landscapes for FlightGear)

I now need to combine several image tiles into one,

see the g.region and r.patch modules:

g.region rast=map1,map2,map3,...
r.patch in=map1,map2,map3,... out=patched map

reduce their resulting size, etc.

see the 'g.region res=' and r.resamp.* modules.

Basically, I'd like to be able to view the imagery as a set
of combined images and then be able to output areas at specific
pixel resolutions.

sure, sounds perfectly reasonable.

Hamish