Ladies and Gentlemen,
I hope someone can help me.
I have some raster (cell) data files in a lat-lon projection, and would
like to extract relevant sections and convert to UTM and save into an
appropriate UTM mapset.
The problem is that I can't remember how to do this (or even if I have
been able to do so in the past...age has its difficulties!), nor can I
find any GRASS commands which seem to fit the bill.
Any help or advice will be gratefully appreciated.
Cheers,
--
Terry Duell, Senior Mobility Engineer
Army Technology & Engineering Agency
Maribyrnong, Victoria, Australia
ph:61-3-93195837 fax:61-3-93195830
Terry Duell wrote:
Ladies and Gentlemen,
I hope someone can help me.
I have some raster (cell) data files in a lat-lon projection, and would
like to extract relevant sections and convert to UTM and save into an
appropriate UTM mapset.
The problem is that I can't remember how to do this (or even if I have
been able to do so in the past...age has its difficulties!), nor can I
find any GRASS commands which seem to fit the bill.
Any help or advice will be gratefully appreciated.
Cheers,
--
Terry Duell, Senior Mobility Engineer
Army Technology & Engineering Agency
Maribyrnong, Victoria, Australia
ph:61-3-93195837 fax:61-3-93195830
The only method I can think of is to convert the raster to a vector
using r.poly, then use v.proj to do the projection converstion to UTM.
Before using v.proj, however, be sure you have a DATUM_INFO file in the
PERMANENT mapsets of both locations. Here's the contents of DATUM_INFO
for the clarke66 spheroid in the continental US:
datum: nad27
region: conus
You will have to change these values appropriately. Then convert your
vector back to raster using v.to.rast.
Method 2: I remember some talk about a command r.proj a couple years
ago, but I don't know if it was ever done. I believe Dr. Simon Cox,
also from Australia, was working on it. Any other old-timers remember
this?
On Thu, 17 Sep 1998, Bruce Nielsen wrote:
(lines deleted)
Method 2: I remember some talk about a command r.proj a couple years
ago, but I don't know if it was ever done. I believe Dr. Simon Cox,
also from Australia, was working on it. Any other old-timers remember
this?
Simon wrote a shell script called r.proj, which I will be glad to pass
along in its 1997 flavor. Below is a brief description of it. I also
checked the ftp site on the moon (moon.cecer.army.mil) and found a
different r.proj, written by Martin Schroeder of the University of
Heidelberg, which claims to work under floating-point GRASS only.
Please note Simon's disclaimer regarding _large_ ascii intermediate
files! Make sure that you consider the consequences of going from a
run-length encoded binary file to an uncompressed ascii file. Also note
that you must have s.sample on your system.
Regards,
-Malcolm Williamson
-------
# r.proj
# copies a cell-map from one GRASS location to another
# using the PROJ_INFO parameters to re-project the map
# and the current region settings to determine the location, size and
resolut
ion
#
# The user must have write permissions in a couple of places
#
# r.proj is a script: it uses
# Gerry Evenden's PROJ program to convert the target cell-locations
to
# the source projection
# Darrell McCauley's s.sample program to resample the source map at
the
# target cell-locations;
# defaults to nearest-neighbour resampling
# (appropriate for "category" maps)
# but can also use bilinear or cubic interpolation
# (appropriate for "continuous" maps)
#
# Only tested for a limited range of projections.
# The intermediate file is ascii so can be very large.
# The s.sample stage takes a while (!) if the map is large.