[Proj] Proj Digest, Vol 58, Issue 10

[Stephan Holl]

Hallo Richard,

Richard Greenwood <richard.greenwood at gmail.com>, [20090312 - 06:54:22]

> On Thu, Mar 12, 2009 at 2:24 AM, Stephan Holl
> <stephan.holl at intevation.de> wrote:
> > Hello Richard,
> >
> > proj-request at lists.maptools.org, [20090311 - 12:00:02]
> >
> >> Date: Wed, 11 Mar 2009 06:34:19 -0600
> >> From: Richard Greenwood <richard.greenwood at gmail.com>
> >> Subject: Re: [Proj] Errors between proj 4.5 and 4.6.1 with
> >> epsg:31467 To: "PROJ.4 and general Projections Discussions"
> >>       <proj at lists.maptools.org>
> >> Message-ID:
> >>       <ae9185aa0903110534lef72ea1n6ccd516277a78497 at mail.gmail.com>
> >> Content-Type: text/plain; charset=ISO-8859-1
> >>
> >> On Wed, Mar 11, 2009 at 4:07 AM, Stephan Holl
> >> <stephan.holl at intevation.de> wrote:
> >> > Dear proj-users,
> >> >
> >> > a customer has updated a test-server from proj 4.5.0 to 4.6.1
> >> > linked to a PostGIS-DB and a UMN MapServer with a WMS on top.
> >> >
> >> > The result of the identical WMS-request on a server working with
> >> > proj 4.5.0 and 4.6.1 have different results in their accurancy,
> >> > about a 100m north-shift.
> >> >
> >> > Did anybody came accross this problem?
> >> >
> >> > I tried to scan the ChangeLog of 4.6.1 but did not find any
> >> > relevant entries which might be the cause of this change.
> >> >
> >> > TIA.
> >>
> >> Stephan,
> >>
> >> >From PROJ 4.6.0 on datum shifts are only applied if datum
> >> >information
> >> for both the source and destination coordinate systems is defined.
> >> EPSG:31467 defines a datum. I am guessing that is the coordinate
> >> system of your source data. Do you know what coordinate system the
> >> WMS request is asking for, and does that coordinate system have a
> >> datum defined, or twgs84 parameters?
> >
> > Thanks for your quick answer. This is good news, but I am not quite
> > sure which values to add so that the results will be identical of
> > the proj 4.5.0-version.
> >
> > I do have a source-projection of epsg:25832 which is defined (in
> > both pproj4.5.0 and 4.6.1) as
> > # ETRS89 / UTM zone 32N
> > <25832> +proj=utm +zone=32 +ellps=GRS80 +units=m +no_defs  <>
> >
> > So towgs84 is missing here and I have to add this here in my
> > MapFile?
> >
> > So adding a +datum=wgs84 will suffice?
> >
> > TIA
> >
> >        Stephan
> >
> > --
> > Stephan Holl <stephan.holl at intevation.de> | Tel.: +49 (0)541-33 508
> > 3663 Intevation GmbH, Neuer Graben 17, 49074 OS  |  AG Osnabrück -
> > HR B 18998 Geschäftsführer:  Frank Koormann, Bernhard Reiter, Dr.
> > Jan-Oliver Wagner
> >
> 
> Yes, that should work. I notice that it is usually upper case:
> +datum=WGS84, or adding +towgs84=0,0,0 should do the trick also.

Confirmed, this worked. I accidently must have missed the change in the
readmes...
Thank you for your help

	Stephan

-- 
Stephan Holl <stephan.holl at intevation.de> | Tel.: +49 (0)541-33 508 3663
Intevation GmbH, Neuer Graben 17, 49074 OS  |  AG Osnabrück - HR B 18998
Geschäftsführer:  Frank Koormann, Bernhard Reiter, Dr. Jan-Oliver Wagner
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