Nikos Alexandris wrote:
On Mon, 2009-02-16 at 11:35 +0000, John Stevenson wrote:
Hi,
I have two questions, first a specific one, secondly a more general one.
1) I have some aerial photos that I want to mosaic. I am able to do
this with r.patch. However, the photos only cover about half of the
region. In the remainder of the region, I would like to show a shaded
relief map as a background to give context to the photos. When I
include the shaded relief map in the list to patch, it comes out as
varying shades of red. My question is therefore, what do I have to do
to the shaded relief map to turn it into an 'rgb image' that I can
include in r.patch.
Do you really want to patch the "shaed relief" map along with the
orthophotos in one map? What about r.blend?
If you insist on patching, then, I think, you would need to create 3 new
versions of your shaded map which will correspond to R(ed), G(reen) and
B(lue), rescale them to 0,255 (r.rescale). Then you patch them with the
R, G and B mosaic's of the orthophotos and compose (r.composite) an RGB
map.
I would expect the shaded part to look grey-scaled since you will have
the same pixel value in all of the R, G and B layers. But I am 100% sure
that it will work.
Thanks Nikos,
In the end, I made a composite from the original shaded relief:
r.composite red="nesja_shade" green="nesja_shade"
blue="nesja_shade" levels=32 output="elev_shade_comp"
then patched it with the photos:
r.patch
input="p43_trimmed,p44_trimmed,p33_trimmed,elev_shade_comp"
output="aerial"
This gave me coloured aerial photos where the data exist, and a grey
shaded relief map where they don't.
2) More generally, what is the best way of converting a good-looking
map into a georeferenced image e.g. by converting the elevation data
into rgb pixel colour data. Currently I would use d.out.file then
gdal_translate, but that is dependent on the screen resolution.
What about "d.out.file in=YourMap out=YourMap resolution=2 # or
resolution=4" ?
Good point.
Cheers
John
Kind regards, Nikos
--
Dr John Stevenson
Postdoctoral Research Associate
School of Earth, Atmospheric and Environmental Sciences
Williamson Building (Room 2.42)
University of Manchester
Manchester M13 9PL, UK
tel. +44(0)161 306 6585; fax. +44(0)161 306 9361;
[email protected]
_______________________________________________
grass-user mailing list
[email protected]
http://lists.osgeo.org/mailman/listinfo/grass-user
