[GRASS-user] European Datum 1950 is not saved in the region information

GRASS GRASS user
1

Hi,
I've set up a location (GRASS 6.4.2. RC1487 15M (2011)), using the Location
wizard, by selecting the coordinate system parameters as so:

projection: UTM
datum with ellipsoid: projection zone 30N
datum code: eur50 (European datum 1950)

when I run g.region -p I get the following:

projection: 1 (UTM)
zone: 30
datum: ** unknown (default: WGS84) **
ellipsoid: international

Is it a problem that the datum has not been saved as European datum 1950?

The reason I'm asking is that when I pull a vector map from this location
into a location with the following projection parameters
projection: 3 (Latitude-Longitude)
zone: 0
datum: wgs84
ellipsoid: wgs84

I get slightly different re-projected coordinates than a colleague who does
the same process in ArcGIS. I would like to confirm that the UTM location is
set up correctly.

Many thanks for your help,

Sophie

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2

On Thu, Nov 3, 2011 at 1:45 PM, thirza <sophiav@gmail.com> wrote:

Hi,
I've set up a location (GRASS 6.4.2. RC1487 15M (2011)), using the Location
wizard, by selecting the coordinate system parameters as so:

projection: UTM
datum with ellipsoid: projection zone 30N
datum code: eur50 (European datum 1950)

when I run g.region -p I get the following:

projection: 1 (UTM)
zone: 30
datum: ** unknown (default: WGS84) **
ellipsoid: international

Is it a problem that the datum has not been saved as European datum 1950?

Yes, this is to be fixed in GRASS.

@devs: I tried

[neteler@north grass64]$ svn diff lib/proj/
Index: lib/proj/convert.c

--- lib/proj/convert.c (revision 49030)
+++ lib/proj/convert.c (working copy)
@@ -724,6 +724,8 @@
     "WGS_1984",
     "World_Geodetic_System_1972",
     "WGS_1972",
+ "eur50",
+ "European_1950",
     "European_Terrestrial_Reference_System_89",
     "European_Terrestrial_Reference_System_1989",
     "European_Reference_System_1989",

... to no avail. Any idea?

Markus

3

Thank you for investigating.

I have the same problem with another projection for the Finland Uniform
Coordinate System:

I've set up a location by selecting the EPSG code 2393 and when I run
g.region -p I get the following:

projection: 99 (Transverse Mercator)
zone: 0
datum: ** unknown (default: WGS84) **
ellipsoid: international

I get the same result if I create the location using a .prj file:

PROJCS["KKJ / Finland Uniform Coordinate
System",GEOGCS["KKJ",DATUM["D_KKJ",SPHEROID["International_1924",6378388,297]],PRIMEM["Greenwich",0],UNIT["Degree",0.017453292519943295]],PROJECTION["Transverse_Mercator"],PARAMETER["latitude_of_origin",0],PARAMETER["central_meridian",27],PARAMETER["scale_factor",1],PARAMETER["false_easting",3500000],PARAMETER["false_northing",0],UNIT["Meter",1]]

Is there any way to set the datum once the location has been created?

Many thanks for your help,

Sophie

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4

Sophia wrote:

I have the same problem with another projection for the
Finland Uniform Coordinate System:

I've set up a location by selecting the EPSG code 2393 and
when I run g.region -p I get the following:

projection: 99 (Transverse Mercator)
zone: 0
datum: ** unknown (default: WGS84) **
ellipsoid: international

I get the same result if I create the location using a .prj
file:

PROJCS["KKJ / Finland Uniform Coordinate
System",GEOGCS["KKJ",DATUM["D_KKJ",SPHEROID["International_1924",6378388,297]],PRIMEM["Greenwich",0],UNIT["Degree",0.017453292519943295]],PROJECTION["Transverse_Mercator"],PARAMETER["latitude_of_origin",0],PARAMETER["central_meridian",27],PARAMETER["scale_factor",1],PARAMETER["false_easting",3500000],PARAMETER["false_northing",0],UNIT["Meter",1]]

Is there any way to set the datum once the location has
been created?

do you use proj4 version 4.7.1svn? If so, please try version 4.7.0
& let us know what you learn please :slight_smile:

thanks,
Hamish

5

hamish-2 wrote:

do you use proj4 version 4.7.1svn? If so, please try version 4.7.0

Sorry, can you give me information on how to use version 4.7.0. I've
downloaded the zip file from http://trac.osgeo.org/proj/ but I'm not sure
what to do with the files. I assuem I must compile it.

I was able to set the datum using g.setproj, then g.proj -p shows the datum
and towgs84 params correctly:

-PROJ_INFO-------------------------------------------------
name : Universal Transverse Mercator
datum : eur50
towgs84 : -87.000,-98.000,-121.000
proj : utm
ellps : international
a : 6378388.0000000000
es : 0.0067226700
f : 297.0000000000
zone : 30
-PROJ_UNITS------------------------------------------------
unit : meter
units : meters
meters : 1.0

However, when I try the same for the Finland Uniform Coordinate System
(created through the wizard selecting EPSG code 2393) g.setproj doesn't find
the D_KKJ datum,

Thanks, Sophie

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6

Hamish wrote:

> do you use proj4 version 4.7.1svn? If so, please try
> version 4.7.0

Sophia:

Sorry, can you give me information on how to use version
4.7.0. I've downloaded the zip file from http://trac.osgeo.org
/proj/ but I'm not sure what to do with the files. I assuem I
must compile it.

actually you just have to replace the "epsg" file with an older
copy,

rename the file C:\Program Files\GRASS 6.4.SVN\proj\epsg
to something like "epsg.471dev"

then download the older 4.7.0 copy from here:
http://trac.osgeo.org/proj/export/2118/tags/4.7.0/proj/nad/epsg

and put it in the same place as "epsg" & hope for the best.

I was able to set the datum using g.setproj, then g.proj -p
shows the datum and towgs84 params correctly:

-PROJ_INFO-------------------------------------------------
name : Universal Transverse
Mercator
datum : eur50
towgs84 : -87.000,-98.000,-121.000
proj : utm
ellps : international
a : 6378388.0000000000
es : 0.0067226700
f : 297.0000000000
zone : 30
-PROJ_UNITS------------------------------------------------
unit : meter
units : meters
meters : 1.0

Yes, g.setproj uses GRASS's internal datum tables to set things
up, so it isn't affected by the epsg file problems & works ok.
On the downside, g.setproj doesn't know about EPSG codes and
so can't expand from them.

However, when I try the same for the Finland Uniform
Coordinate System (created through the wizard selecting EPSG
code 2393) g.setproj doesn't find the D_KKJ datum,

the location wizard doesn't use g.setproj, it is a work-alike.
the location wizard uses "g.proj -c" which relies on PROJ.4
for the datum and ellipsoid options, and that's the one which
is not happy right now.

for more details see http://trac.osgeo.org/proj/ticket/122

Hamish