[Mapserver-users] Ccoordinate/projection display problem?

[Ed McNierney]

Gerry -

That's correct.  The PROJECTION object in each location describes the projection of the enclosing object/block.  At the top level in your MAP file you're describing the OUTPUT map image, so that PROJECTION block should describe the output projection - and make sure your EXTENT and UNITS are appropriate for that projection.

The PROJECTION object inside each layer describes the projection of the source raster or vector data in that layer.  If there is no PROJECTION block inside the layer that layer is presumed to be in the same projection as the output map file.

	- Ed

Ed McNierney
President and Chief Mapmaker
TopoZone.com / Maps a la carte, Inc.
73 Princeton Street, Suite 305
North Chelmsford, MA  01863
ed at topozone.com
(978) 251-4242 

-----Original Message-----
From: Gerry Creager N5JXS [mailto:gerry.creager at tamu.edu]
Sent: Saturday, September 13, 2003 12:15 PM
To: Ed McNierney
Cc: Ann Keane; Frank Warmerdam; mapserver-users at lists.gis.umn.edu
Subject: Re: [Mapserver-users] Ccoordinate/projection display problem?


I've been swamped, and consequently lost some of this thread.  I'm 
*still* haveing projection problems, so I'll ask again.  Maybe I'll 
understand what's going on...

If, in my mapfile I want to have the final projection in Lambert 
Conformal Conic, but all of my data are Lat/Lon unprojected, then, the 
PROJECTION section of the top layer is LCC, while the projection info in 
all the layers would be LAT-LON?  Or is this inverted?

Confusedly yours,
Gerry

Ed McNierney wrote:
> Ann -
> 
> Actually, the EPSG code IS a complete description - but you were using
> the same code for all your layers in your original map file.
> 
> The EPSG code is, I think, somewhat preferable IF you are using a
> standard projection.  The downside is that it's a little cryptic (a MAP
> file comment would help) but the upside is that it's much harder to make
> typos, and much easier to ensure that two projections that should be the
> same ARE the same.
> 
> 	- Ed
> 
> Ed McNierney
> President and Chief Mapmaker
> TopoZone.com / Maps a la carte, Inc.
> 73 Princeton Street, Suite 305
> North Chelmsford, MA  01863
> Phone: (978) 251-4242  Fax: (978) 251-1396
> ed at topozone.com
> 
> 
> -----Original Message-----
> From: Ann Keane [mailto:Ann.Keane at noaa.gov] 
> Sent: Friday, September 12, 2003 7:31 PM
> To: Frank Warmerdam
> Cc: mapserver-users at lists.gis.umn.edu; Ed McNierney
> Subject: Re: [Mapserver-users] Ccoordinate/projection display problem?
> 
> 
> Ed and Frank-
> 
> Thank you both.  You were correct in that I was not completly describing
> 
> the coordinates and projection.  This is all well beyond what I think I 
> know about cartography, so I thought the epsg code was the complete 
> description.  listgeo -proj4 will be invaluable to me.  We're just 
> getting started with the project so I've been using the full data files.
> 
>    The suggestions about reprojecting will be very helpful when we start
> 
> running the system operationally.
> 
> The resulting projection was:
> PROJECTION
> "+proj=laea +lat_0=45.000000000 +lon_0=-100.000000000 +x_0=0.000 
> +y_0=0.000 +ellps=WGS84 +units=m"
> END
> 
> -Ann
> 
> 
> Frank Warmerdam wrote:
> 
> 
>>If you have
>>listgeo handy you might try running "listgeo -proj4 shdrlfi0201.tif"
> 
> to
> 
>>see what it things is a good "PROJ.4 string" representing the
> 
> coordinate
> 
>>system of the file in question.
>>
>>I would guess you will want something like:
>>
>>PROJECTION
>>  "+proj=laea +lat_0=45 +lon_0=-100 +datum=WGS84"
>>END
>>
>>You can test convert points using the PROJ commandline tools something
> 
> like
> 
>>this:
>>
>>warmerda at gdal2200[29]% cs2cs +proj=laea +lat_0=45 +lon_0=-100 
>>+datum=WGS84 +to +proj=latlong +datum=WGS84
>> -6086629. 4488761                                    (input)
>> 156d3'31.097"E        37d45'55.65"N 0.000            (output)
>>
> 
> 
> 
> 
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-- 
Gerry Creager -- gerry.creager at tamu.edu
Texas Mesonet -- AATLT, Texas A&M University	
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