[GRASS-user] Identification of projectiopn?

Tue Jul 5 07:17:50 EDT 2011

On Tue, Jul 5, 2011 at 1:05 PM, Daniel Lee <lee at isi-solutions.org> wrote:

> That really is a guessing game, because even if someone finds the
> coordinates that the map could fit into, it still doesn't mean that they're
> correct. Do you have a reason to think that the datum is WGS84? I think
> South Africa probably uses a more accurate regional datum for local maps -
> that makes a lot more sense unless you're working directly with web mapping
> applications or you want to use GPS data directly.
>

Yes - everybody is using WGS84, because it comes from a GPS - and
reprojection usually is to be avoided because it is difficult to understand
(I am allowed this statement - I have lived in SA and really loved it
there!).

> Isn't there any metadata provided with the shapefiles? I didn't know that
> it was possible to have a shapefile without any kind of spatial reference
> stored in the metadata. You could try making a location based on the
> shapefile as a georeferenced file.
>

Well - as far as I know, the projection info comes in a .prj file (missing)
and the .shp file efectively contains the points, dbf the attribute table
and the shx the spatial index - no metadata.
All the data I have is the data - no metadata.
Here is the output from ogrinfo:

$ ogrinfo kcla_boundary.shp
INFO: Open of `kcla_boundary.shp'
      using driver `ESRI Shapefile' successful.
1: kcla_boundary (Line String)
rkrug at ecolmod:~/Documents/Projects/HakeaLandscape/trunc/GIS/locations/Keurboom/region$
ogrinfo -al kcla_boundary.shp
INFO: Open of `kcla_boundary.shp'
      using driver `ESRI Shapefile' successful.

Layer name: kcla_boundary
Geometry: Line String
Feature Count: 1
Extent: (17001.174423, -3754438.151804) - (37019.926542, -3743929.774592)
Layer SRS WKT:
(unknown)
ID: Integer (8.0)
OGRFeature(kcla_boundary):0
  ID (Integer) = 0
  LINESTRING (36961.220524529955583
-3748802.374081357847899,34701.038833641323436
-3749477.493287727236748,30885.147667205979815
-3747804.371776290237904,26218.019240565823566
-3746336.721327661070973,21316.066742145034368
-3743929.774591909721494,19877.769302488635731
-3745749.661148209590465,18821.060979475769273
-3745544.19008540129289,17470.822566737107991
-3746160.603273825719953,17001.174423175834818
-3748362.078946769237518,21169.301697282135137
-3750152.612494096625596,24368.77967529331363
-3750181.965503069106489,26276.725258510985441
-3751855.087014506105334,28360.788895564135601
-3753234.678436217363924,30591.617577480181353
-3754438.151804093271494,32323.44510686238209
-3753674.973570805974305,27715.022698167384078
-3751708.321969643235207,27509.55163535932661
-3750739.672673548106104,30180.675451864066417
-3750035.200458206236362,34025.919627271992795
-3751737.6749786157161,37019.92654247511382 -3748861.080099302809685)

Thanks,

Rainer

> Best,
> Daniel
>
> --
> B.Sc. Daniel Lee
> Geschäftsführung für Forschung und Entwicklung
> ISIS - International Solar Information Solutions
>
> Deutschhausstr. 10
> 35037 Marburg
> Festnetz: +49 6421 379 6256
> Mobil: +49 176 6127 7269
> E-Mail: Lee at isi-solutions.org
> Web: http://www.isi-solutions.org
> Am 05.07.2011 12:59 schrieb "Rainer M Krug" <r.m.krug at gmail.com>:
>
> > Hi
> >
> > I have two shape files of which I do not know the projection (and it
> seems
> > that the person I got them from does not know either...). The maps are
> from
> > the Keurboom nature reserve area in South Africa (
> > http://plak.co.za/moreinfo.php?id=347) and the two shp files have the
> > folowing bounding boxes:
> >
> >
> > In layer spatial reference system units : xMin,yMin 21340.4,-3755528.75 :
> > xMax,yMax 34244.9,-3749187.87
> >
> > In layer spatial reference system units : xMin,yMin 17001.2,-3754438.15 :
> > xMax,yMax 37019.9,-3743929.77
> >
> >
> > I know this is a guessing game, but it must be a common projection - the
> map
> > datum is very likely (almost certainly) WGS84.
> >
> >
> > Any suggestions welcome,
> >
> >
> > Rainer
> >
> >
> > --
> > Rainer M. Krug, PhD (Conservation Ecology, SUN), MSc (Conservation
> Biology,
> > UCT), Dipl. Phys. (Germany)
> >
> > Centre of Excellence for Invasion Biology
> > Stellenbosch University
> > South Africa
> >
> > Tel : +33 - (0)9 53 10 27 44
> > Cell: +33 - (0)6 85 62 59 98
> > Fax (F): +33 - (0)9 58 10 27 44
> >
> > Fax (D): +49 - (0)3 21 21 25 22 44
> >
> > email: Rainer at krugs.de
> >
> > Skype: RMkrug
>

-- 
Rainer M. Krug, PhD (Conservation Ecology, SUN), MSc (Conservation Biology,
UCT), Dipl. Phys. (Germany)

Centre of Excellence for Invasion Biology
Stellenbosch University
South Africa

Tel :       +33 - (0)9 53 10 27 44
Cell:       +33 - (0)6 85 62 59 98
Fax (F):       +33 - (0)9 58 10 27 44

Fax (D):    +49 - (0)3 21 21 25 22 44

email:      Rainer at krugs.de

Skype:      RMkrug
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