[GRASS-dev] datums not recognized by g.proj?

[Michael Barton]

Just tested on GRASS 7 and it looks like it works very well.

PROJ.INFO file created using projection and datum selection in location wizard BEFORE updating

name: Universal Transverse Mercator
proj: utm
ellps: international
zone: 29
no_defs: defined

PROJ.INFO file recreated by g.proj AFTER updating

name: Universal Transverse Mercator
proj: utm
ellps: international
zone: 29
no_defs: defined
datum: eur50
towgs84: -131,-100.3,-163.4,-1.244,-0.020,-1.144,9.39

Using the new g.proj with datumtrans=-1 brings up the list of datum transforms for "eur50" as it should. 

I will update the location wizard code in trunk shortly to take advantage of this. If others can then test, we should backport to 6.4.3.

Thanks so much. Serious problem identified over the weekend and fixed by Monday night. I can tell my class tomorrow. Wow.

Michael

____________________
C. Michael Barton
Director, Center for Social Dynamics & Complexity 
Professor of Anthropology, School of Human Evolution & Social Change
Arizona State University

voice: 	480-965-6262 (SHESC), 480-727-9746 (CSDC)
fax:          480-965-7671 (SHESC),  480-727-0709 (CSDC)
www: http://www.public.asu.edu/~cmbarton, http://csdc.asu.edu











On Oct 1, 2012, at 2:44 PM, Paul Kelly <paul-grass at stjohnspoint.co.uk> wrote:

> Markus Neteler wrote:
>> 
>> I do agree that getting the datum lost is bad. Perhaps we could enhance
>> g.proj to write it to PROJ_INFO when using the "Select coordinate system" way
>> of creating locations. Proof of concept:
>> 
>> GRASS 6.4.3svn (newLocation2):~ > eval `g.gisenv`
>> 
>> GRASS 6.4.3svn (newLocation2):~ > echo "datum: eur50" >>
>> $GISDBASE/$LOCATION_NAME/$MAPSET/PROJ_INFO
> 
> I have just committed r53297 to trunk, which adds a new datum= option to g.proj, which does something very similar to this. If a GRASS datum code is given for the datum= option, it will override any datum in the input co-ordinate system (or add one if it is missing).
> 
> So you can now do something like:
> g.proj -c loc=spain proj4="+proj=utm +zone=30 +ellps=intl" \
> datum=eur50 datumtrans=-1
> which will correctly prompt for all the datum transformation options for eur50. You can also do
> g.proj datum=list
> to get a list of all supported datums like g.setproj does, but in a more easily parseable format similar to the output from datumtrans=-1.
> 
> Hope that helps a bit.
> 
> Paul