[mapserver-users] DATUM CONVERSIONS

[Jaime Mejía]

hi  list,

I've got a base map in XY coordinates with datum bogota.
In the map file, I've got the following projection definition:

-----------------------------------------------------------------------------------------------------------
# Start of map file
#
NAME BOGOTA
STATUS ON
SIZE 600 600
SYMBOLSET "/usr/local/apache/htdocs/bog/symbols/symbol.sym"
EXTENT 250000 20000 2110000  1880000
UNITS METERS
SHAPEPATH "/usr/local/apache/htdocs/bog/data/"
IMAGECOLOR 240 240 240
FONTSET "/usr/local/apache/htdocs/bog/fonts/fonts.txt"

# View Projection definition
PROJECTION
  "proj=tmerc"
  "ellps=intl"
  "k=0.9996"
  "x_0=1000000"
  "y_0=1000000"
  "lon_0=74d4.8550002'w"
  "lat_0=4d35.9428332'n"
END
-----------------------------------------------------------------------------------------------------------
And I want to display in the map a collection of points taken with a GPS 
and datum WGS84.
How do I define the projection in the layer?

If I take the points with GPS datum BOGOTA it appears where they should, 
but with WGS84 it
appears +/- 500 mts displaced to the south-east

I've got the projection in the layer defined this way:

PROJECTION
    "proj=latlong"
    "ellps=WGS84"
 END

The problem is that there is about 500.000 points, so it is impossible 
to take them again with
datum BOGOTA.

I used a Garmin GPS

What should I do?

Thanks in advance,

-- 
Cordial Saludo,

MAIN TASK

Jaime Mejía Molina
www.main-task.com
Teléfono 2184608
DG 85 # 28-39
Bogotá D. C.