Projection WGS84 in decimal degree

[Ed McNierney]

FP -
 
Your first GPS layer definition should be fine.  You don't say what data
source you are using for your GPS data, but if it is a shapefile or
inline features you will be using decimal degrees and those will work
fine with the "init=epsg:4326" definition.
 
The first thing I would suggest is that you confirm that the EPSG:27582
projection is in fact correct. The related Paris / Lambert projections
(27581-27584, for example) are all rather similar and can certainly look
the same.  Can you check the coordinates of a few points to make sure
they're accurate?  An error of 200km is far too large to be a datum
error, but could easily be due to the different false easting/northing
values used in these similar projections.
 
     - 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 


________________________________

From: UMN MapServer Users List [mailto:MAPSERVER-USERS at LISTS.UMN.EDU] On
Behalf Of zze-SIGALE PORTANERI F ext RD-BIZZ-SOP
Sent: Wednesday, January 11, 2006 7:20 AM
To: MAPSERVER-USERS at LISTS.UMN.EDU
Subject: [UMN_MAPSERVER-USERS] Projection WGS84 in decimal degree




Hi all, 

I have a set of WGS84 data points that come from GPS system in decimal
degree longitude/latitude coordinates. 
I would like to display them with mapserver using a mapfile which
already define several layers in Lambert II. 

I did specified the global projection in the mapfile for Lambert II
etendu : 

PROJECTION
"init=epsg:27582"
END

The GPS LAYER describing the WGS84 data includes the projection
definition for the WGS84 : 
LAYER
  NAME "GPS"
  PROJECTION
    "init=epsg:4326"
  END
  ...
END 
But points are not displayed at the right place (at about 200km far
away)  :-( 
Apparently, the 4326 epsg definition considers longitude/latitude
coordinates in Degree/Minute/Second, while my data are in Decimal
Degrees.

So I tried to specify the following in the GPS layer :

PROJECTION
"proj=longlat"
"ellps=WGS84"
"datum=WGS84"
"units=dd"
END


but mapserver returns: "Error in msProcessProjection(): unknown unit
conversion id" 
The prog -lu command doesn't list the "dd" unit... 
How to display longlat data in Decimal Degree under Mapserver?

Regards 
FP 

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