specific development discussions on the Cartographic Projections Library (PROJ.4)

peter | 2 Dec 2007 05:22

3TM projection string

Greetings all,

I'm working with map data from Lethbridge, Alberta, Cananda that's in NAD83 
3TM projection. I'm having trouble locating details about the projection 
other than it's a 3 degree projection with -114 as the cental meridian. I'm 
working with qgis and I tried copying one of the other MTM projections and 
changing it to: 

+proj=tmerc +lat_0=0 +lon_0=-114 +k=0.999900 +x_0=304800 +y_0=0 +ellps=GRS80 
+datum=NAD83 +units=m +no_defs

Would this work? Thanks so much.

--

-- 
Peter Pankonin, digitalcrucible

There are 10 kinds of people in the world,
those who understand binary, and those who don't.
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uwe.schmitz | 3 Dec 2007 12:56

AW: PROJ 4.6.0 beta1 Release

Frank,

> uwe.schmitz <at> lverma.nrw.de wrote:
> > Frank,
> > 
> > I am using the example from ticket 1531 with a local
> > (may be this is the problem?) grid file (attached
> > to the ticket).
> > 
> > The shell script:
> > export PROJ_DEBUG=1
> > cs2cs \
> >       -f "%.12f" \
> >       +proj=latlong \
> >       +ellps=bessel \
> >       +nadgrids=./tstgrid.gsb \
> >    +to \
> >       +proj=latlong \
> >       +ellps=GRS80 \
> >       <<EOF
> > 7.483333333333E 53.500000000000N
> > EOF
> 
> Uwe,
> 
> But in this case the output coordinate system only has an ellipse, and
> no datum definition, so pj_transform() deliberately makes no 
> attempt to
> do a datum shift.  This is exactly the sort of case in which 
> the behavior

(Continue reading)

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Frank Warmerdam | 3 Dec 2007 16:57

Re: AW: PROJ 4.6.0 beta1 Release

uwe.schmitz <at> lverma.nrw.de wrote:
> oh yes, my fault! It shows me that I didn't really understand
> what I'm doing with PROJ.4 
> 
> OK, if I add "+datum=WGS84" to the "+to" part I get the same
> result as with V4.5.0 (still wrong in respect of ticket 1531).
> Despite that, isn't it true that the grid file contains 
> datum definition for both (from and to) system?  So isn't
> it better to assume datum definition for both systems, if
> a grid is specified? 

Uwe,

PROJ.4 implicitly assumes that datum grids map from the
local datum to WGS84 but the output coordinate system can
be other than WGS84 so I don't agree that the nadgrids
implies the whole transformation.

 > What also confuses is that the destination
> datum isn't really WGS84 in this case, but the slightly 
> different ETRS89.

Because the PROJ nadgrids directive does not understand that
there can exist grids going to coordinate systems other than
WGS84 it is necessary to fool it. So you declare your output
coordinate system as +datum=WGS84 but *you* know that you want
to inteprete the output coordinates as ETRS89.

> Anyhow, I think the change breaks backward compatibility and this
> has to be documented very well. All of my old scripts have to

(Continue reading)

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Richard Greenwood | 4 Dec 2007 05:10

Re: PROJ 4.6.0 beta1 Release

On Nov 30, 2007 7:40 AM, Frank Warmerdam <warmerdam <at> pobox.com> wrote:

> If either coordinate system passed to pj_transform() lacks a datum
> definition then it will be assumed that it's datum effectively
> matches the other.

For what it's worth, MapInfo does that same thing. This behavior has
caught me off guard a few times, but it's really pretty logical.

Rich

--

-- 
Richard Greenwood
richard.greenwood <at> gmail.com
www.greenwoodmap.com
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Roger Oberholtzer | 7 Dec 2007 16:26

Re: Re: Proj Digest, Vol 42, Issue 8

On Fri, 2007-11-30 at 11:47 +0100, Jordi Gilabert Vall wrote:
> I use these 7 coefficients with cartography in Catalonia (Spain), with
> right results:
> 
> cs2cs +proj=latlong +datum=WGS84 +ellps=WGS84 +to +init=epsg:23031
> +proj=utm +ellps=intl +zone=31 +units=m +towgs84=-
> 131.0320,-100.2510,-163.3540,1.2438,0.0195,1.1436,9.3900

I have finally had a chance to check this. Sorry it took so long. I do
not get much difference. Could you give me a few sample lat/longs and
the northings/eastings you get with this command? I did have to change
the zone to 30 for Madrid for my tests, os the derived values were very
far off.

> 
> 
> More information:
> 
> http://www.euref-iag.net/symposia/book2003/4-6.pdf
> 
> http://www.fomento.es/NR/rdonlyres/8B4D8323-5706-4F8F-84F7-C89774DCC2A1/29826/hercam.pdf
> 
> 
> Jordi Gilabert Vall
> 
>         ---------------------------------------------------------------------- 
>         
>         Message: 1
>         Date: Thu, 29 Nov 2007 14:55:17 +0100
>         From: Roger Oberholtzer <roger <at> opq.se>

(Continue reading)

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Gianfranco Arcieri | 7 Dec 2007 17:54

Proj4 on Windows Vista

I am not able to run Proj4 on Vista with Visual Studio 2005. The same dll with the same code runs great on Windows Xp.
Any help is appreciated

Gianfranco

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Mateusz Loskot | 7 Dec 2007 20:27

Re: Proj4 on Windows Vista

Gianfranco Arcieri wrote:
> I am not able to run Proj4 on Vista with Visual Studio 2005. The same dll
> with the same code runs great on Windows Xp.
> Any help is appreciated

Do you build PROJ.4 yourself?
Have you installed Service Pack 1 for Visual Studio 2005?
What error/message/... you are getting?

Cheers
--

-- 
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http://mateusz.loskot.net
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Gianfranco Arcieri | 10 Dec 2007 10:19

Re: Proj4 on Windows Vista

Thanks for your suggestions.
I had sp1 for VS2005. I both used the 446 proj version already built for windows and also I compiled on Vista the new 4.5 version. In both cases it did not work. The message I get is Access Violation every time I try to call something like prj.ToString()
or pj_init or pj_get_errno_ref()

Regards
Gianfranco

On Dec 7, 2007 8:27 PM, Mateusz Loskot <mateusz <at> loskot.net> wrote:

Gianfranco Arcieri wrote:
> I am not able to run Proj4 on Vista with Visual Studio 2005. The same dll
> with the same code runs great on Windows Xp.
> Any help is appreciated

Do you build PROJ.4 yourself?
Have you installed Service Pack 1 for Visual Studio 2005?
What error/message/... you are getting?

Cheers
--
Mateusz Loskot
http://mateusz.loskot.net
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Tran, Toan (MCYS | 10 Dec 2007 17:32

Data Plotted at Wrong Location

Hi,

I wish to plot several points in Canada, but the problem is that the points are plotted at the wrong location. My data are in decimal degree stored in a CSV file. I am guessing that Map Server plots the points in meters instead of degree.

I used this in my map layer:
PROJECTION
"init=epsg:42304"
END

I added this for epsg:
<42304> +proj=lcc +lat_1=49 +lat_2=77 +lat_0=49 +lon_0=-95 +x_0=0 +y_0=0 +ellps=GRS80 +datum=NAD83 +units=m +no_defs no_defs <>

I try changing:
- <42304> +proj=lcc +lat_1=49 +lat_2=77 +lat_0=49 +lon_0=-95 +x_0=0 +y_0=0 +ellps=GRS80 +datum=NAD83 +units=dd +no_defs no_defs <> .... this causes a msProcessProjection(): Projection library error. unknown unit conversion id error

- UNITS METERS to UNITS DD in my map file, but that doesn't help.

Sample DATA:
<<img.GIF>>
"AAAAAAAAAAAAAAAAAAAAAAaaaaaa19",0,200000
"AAAAAAAAAAAAAAAAAAAAAAaaaaaa20",0,220000
"AAAAAAAAAAAAAAAAAAAAAAaaaaaa21",0,240000
"AAAAAAAAAAAAAAAAAAAAAAaaaaaa30",0,300000
"AAAAAAAAAAAAAAAAAAAAAAaaaaaa31",10000,300000

Any help is much appreciated
Thanks
Toan

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Ed McNierney | 10 Dec 2007 17:57

RE: Data Plotted at Wrong Location

Toan –

This is probably a better question for the MapServer list, but you’re on the wrong path. Put the 42304 definition back the way it was – that’s correct.

The EPSG:42304 projection is a Lambert Conformal Conic projection, and I assume that’s what you want to use for your OUTPUT map image. Its units are not in decimal degrees, nor can they be. You have an INPUT data layer in decimal degrees, and you’d like MapServer to reproject that data to your output projection.

Your top-level MAP file needs the PROJECTION definition you describe below, and then you also need to have an appropriate PROJECTION block inside the LAYER definition for the layer in decimal degrees. That tells MapServer that your input and output data are in different projections, and the data need to be reprojected.

The correct EPSG definition for your input data in decimal degrees will depend on what datum those coordinates use.

- Ed

Ed McNierney

Chief Mapmaker

Demand Media / TopoZone.com

73 Princeton Street, Suite 305

North Chelmsford, MA 01863

ed <at> topozone.com

Phone: +1 (978) 251-4242

Fax: +1 (978) 251-1396

From: proj-bounces <at> lists.maptools.org [mailto:proj-bounces <at> lists.maptools.org] On Behalf Of Tran, Toan (MCYS)
Sent: Monday, December 10, 2007 11:32 AM
To: proj <at> lists.maptools.org
Subject: [Proj] Data Plotted at Wrong Location

Hi,

I wish to plot several points in Canada, but the problem is that the points are plotted at the wrong location. My data are in decimal degree stored in a CSV file. I am guessing that Map Server plots the points in meters instead of degree.

I used this in my map layer:
PROJECTION
"init=epsg:42304"
END

I added this for epsg:
<42304> +proj=lcc +lat_1=49 +lat_2=77 +lat_0=49 +lon_0=-95 +x_0=0 +y_0=0 +ellps=GRS80 +datum=NAD83 +units=m +no_defs no_defs <>

I try changing:
- <42304> +proj=lcc +lat_1=49 +lat_2=77 +lat_0=49 +lon_0=-95 +x_0=0 +y_0=0 +ellps=GRS80 +datum=NAD83 +units=dd +no_defs no_defs <> .... this causes a msProcessProjection(): Projection library error. unknown unit conversion id error

- UNITS METERS to UNITS DD in my map file, but that doesn't help.

Sample DATA:
<<img.GIF>>
"AAAAAAAAAAAAAAAAAAAAAAaaaaaa19",0,200000
"AAAAAAAAAAAAAAAAAAAAAAaaaaaa20",0,220000
"AAAAAAAAAAAAAAAAAAAAAAaaaaaa21",0,240000
"AAAAAAAAAAAAAAAAAAAAAAaaaaaa30",0,300000
"AAAAAAAAAAAAAAAAAAAAAAaaaaaa31",10000,300000

Any help is much appreciated
Thanks
Toan

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