[mapserver-users] RE: County Projection Help

[Hankley, Chip]

Figured it out. 

For the sake of the Archive, false easting and northing should be given in
meters. If your data is in feet, use the "to_meter" parameter. So, in my
PROJ4 definition, the following line:

"x_0=245000"

should be

"x_0=74676.149352"

That is, the FGDC Projection specifies a false easting of 245,000 feet (an I
know the image coordinates for the georeferencing are in feet). Apparently
PROJ4 expects false easting to be in meters. So, multiplying:

 245,000 * 0.3048006096 = 74676.149352

Using this value, the data lines right up!

Chip

-----Original Message-----
From: Hankley, Chip 
Sent: Friday, May 10, 2002 8:56 AM
To: MapServer List (E-mail)
Subject: County Projection Help


I'm having trouble writing the PROJ4 definition for the following
projection:

Spatial_Reference_Information:
  Horizontal_Coordinate_System_Definition:
    Planar:
      Map_Projection:
        Map_Projection_Name: Lambert Conformal Conic
        Lambert_Conformal_Conic:
          Standard_Parallel: 45.056389
          Standard_Parallel: 44.745278
          Longitude_of_Central_Meridian: -89.770000
          Latitude_of_Projection_Origin: 44.405556
          False_Easting: 245000
          False_Northing: 0
      Planar_Coordinate_Information:
        Planar_Coordinate_Encoding_Method: 
        Coordinate_Representation:
          Abscissa_Resolution: 
          Ordinate_Resolution: 
        Planar_Distance_Units: survey feet
    Geodetic_Model:
      Horizontal_Datum_Name: North American Datum of 1983 (1991 adjusted)
      Ellipsoid_Name: Geodetic Reference System 1980 (GRS 80)
      Semi-major_Axis: 20923797.3851
      Denominator_of_Flattening_Ratio: 298.274225

This is what I've come up with, but it doesn't seem to be working:

  PROJECTION
    "proj=lcc" 
    "lat_1=45.056389" 
    "lat_2=44.745278" 
    "lat_0=44.405556" 
    "lon_0=-89.770000" 
    "x_0=245000" 
    "y_0=0" 
    "ellps=GRS80"
    "datum=NAD83" #Tried w/ and w/out this line
    "to_meter=0.3048006096"
    "no_defs"
  END

What am I missing. Is there some special way to define the NAD83(91) Datum?
TIA!

Chip Hankley