[Gfoss] Re: [postgis-users] Question on datum names

Sempre a proposito di CRS e datum, segnalo questo interessante thread.
Comments welcome.

-------- Messaggio originale --------
Oggetto: Re: [postgis-users] Question on datum names
Data: Wed, 30 May 2012 00:47:43 +0200
Mittente: Peter Baumann <p.baumann@jacobs-university.de>
Rispondi-a: PostGIS Users Discussion <postgis-users@postgis.refractions.net>
Organizzazione: Jacobs University Bremen
A: PostGIS Users Discussion <postgis-users@postgis.refractions.net>


in OGC (www.opengeospatial.org) we are just about to establish a standard for
such conventions in a machine-readable way. This is a so-called "CRS Name Type
Specification" defines URLs as identifiers for CRSs and CRS axes for now. More
ingredients, such as datums, probably will follow in future. This standard will
allow for a uniform, interoperable addressing scheme.

If you are interested I can post some preliminary information. The candidate OGC
CRS resolver, SECORE, is in beta accessible at http://www.earthlook.org/ ->
demos -> CRS resolver. It is Open Source as part of the array analytics server,
rasdaman (www.rasdaman.org).


On 05/29/2012 11:45 PM, Peter N. Schweitzer wrote:

On the web site from which I distribute spatial data, I provide shapefiles
with projection information as a .prj file. I've drawn the contents of
these prj files from the srtext field of the spatial_ref_sys table.

A user has pointed out to me that this is inconvenient for people running
ArcGIS because ArcGIS expects to see different values as the name of the
coordinate system and the datum. I have not seen a standard that specifies
these names. Is there one?

It looks like I could change my .prj files to fit ArcGIS without much trouble.
But would this change break other applications? Are there GIS applications
other than ArcGIS that rely strongly on these names? How do others support
portability of projection information in downloadable data using the shapefile


Dr. Peter Baumann
- Professor of Computer Science, Jacobs University Bremen
   mail: p.baumann@jacobs-university.de
   tel: +49-421-200-3178, fax: +49-421-200-493178
- Executive Director, rasdaman GmbH Bremen (HRB 26793)
   www.rasdaman.com, mail: baumann@rasdaman.com
   tel: 0800-rasdaman, fax: 0800-rasdafax, mobile: +49-173-5837882
"Si forte in alienas manus oberraverit hec peregrina epistola incertis ventis
dimissa, sed Deo commendata, precamur ut ei reddatur cui soli destinata, nec
preripiat quisquam non sibi parata." (mail disclaimer, AD 1083)

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On Wed, May 30, 2012 at 8:01 AM, Paolo Cavallini <cavallini@faunalia.it> wrote:

Sempre a proposito di CRS e datum, segnalo questo interessante thread.
Comments welcome.

E' un servizio apparentemente "useless" - provate con Gauss-Boaga:
--> mi sembra che manchi il datum geodetco (towgs84), allora è
      pericoloso basarsi su servizi come questo.

Per esempio, GRASS GIS chiede all'utente quale datum geodetico
usare: http://grass.osgeo.org/screenshots/images/grass64_location_wiz3.png

Servizi (e alcuni GIS) non sono in grado di gestire più di un datum
geodetico per codice EPSG.