[gdal-dev] gdaltransform user problems

[Frank Warmerdam]

Jack Kirkpatrick wrote:
> Greetings,
> 
> My apologies in advance if the following is stupid but I am not a GIS 
> expert (probably not even a GIS novice).
> 
> Some time ago I had call to transform corner coordinates from 
> "Australian Geodetic Datum 1966" to WGS84 so that I could accurately 
> drape some nautical charts in GeoTiff format onto Google Earth. I used a 
> utility called GEOTRANS2 which produced excellent mathematical results 
> but is decidely clunky to integrate.
> 
> I recently discovered the GDAL utilities and have been trying to 
> replicate this transformation without success.
> ----------------------------
> 
> I have netted down my efforts as follows:
> 
> (1) Environment is Windows XP SP3 and I have installed FWTools 2.2.9.
> 
> (2) I have a file [C:\fwtest\agd66.wkt] containing:
> 
> GEOGCS["AGD66",
> DATUM["Australian_Geodetic_Datum_1966",
> SPHEROID["Australian National Spheroid",6378160,298.249999999996,
> AUTHORITY["EPSG","7003"]],
> AUTHORITY["EPSG","6202"]],
> PRIMEM["Greenwich",0],
> UNIT["degree",0.0174532925199433],
> AUTHORITY["EPSG","4202"]]

Jack,

Your WKT file does not have any information on how to transform
from AGD66 to WGS84.  Try using:

GEOGCS["AGD66",
DATUM["Australian_Geodetic_Datum_1966",
SPHEROID["Australian National Spheroid",6378160,298.249999999996,
AUTHORITY["EPSG","7003"],
TOWGS84[-133,-48,148]],
AUTHORITY["EPSG","6202"]],
PRIMEM["Greenwich",0],
UNIT["degree",0.0174532925199433],
AUTHORITY["EPSG","4202"]]

I got the TOWGS84 values for AGD66 from the geotrans datum list which
is distributed in GDAL as gdal/data/gt_datum.csv.

Best regards,
-- 
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