[gdal-dev] gdalwarp offset

[szenttehen at yahoo.com]

Hi,
 I need to reproject imagery that is too
big for my GIS software package to handle. I am
testing GDALWARP on some
smaller images make sure I am doing things right
before attempting the big image. It almost works, but
has one problem. The command
I am using is as follows:

gdalwarp -s_srs custer.prj -t_srs IdahoSPl.prj t75.sid
t75_sp.tiff

where custer.prj and idahosp.prj are projection files
as shown below. I am
basically reprojecting from UTM zone 11 to Idaho State
Plane Central (which
is basically a custom projection). 

Everything executes fine, except that when I using the
reprojected imagery
(State Plane) as a background for my layers (which are
in the same
projection) the image is off by about 60 feet to the
east and a 10 feet to
the south. I am sure it is not my vector layers since
they line up exactly
with the image before it is reprojected (The vector
layers are reprojected
"on the fly" to UTM 11 by Manifold GIS when the I
overlay them on the
imagery before reprojection)

It seems that I am missing some offsets or something,
but I don't see how
since I use the .prj parameters from my vector layer
for the target
projection in gdalwarp. Does gdalwarp run into
problems with the change in datums between the two
projections? Any ideas would be helpful.

Thanks,
Joseph
 

Custer.prj
ROJCS["IDTM",GEOGCS["GCS_North_American_1927",DATUM["D_North_American_1927",SPHEROID["Clarke_1866",6378206.4,294.9786982]],PRIMEM["Greenwich",0],UNIT["Degree",0.017453292519943295]],PROJECTION["Transverse_Mercator"],PARAMETER["False_Easting",500000],PARAMETER["False_Northing",100000],PARAMETER["Central_Meridian",-114],PARAMETER["Scale_Factor",0.9996],PARAMETER["Latitude_Of_Origin",42],UNIT["Meter",1]]

idahosp.prj
PROJCS["NAD_1983_StatePlane_Idaho_Central_FIPS_1102_Feet",GEOGCS["GCS_North_American_1983",DATUM["D_North_American_1983",SPHEROID["GRS_1980",6378137.0,298.257222101]],PRIMEM["Greenwich",0.0],UNIT["Degree",0.0174532925199433]],PROJECTION["Transverse_Mercator"],PARAMETER["False_Easting",1640416.666666667],PARAMETER["False_Northing",0.0],PARAMETER["Central_Meridian",-114.0],PARAMETER["Scale_Factor",0.9999473684210526],PARAMETER["Latitude_Of_Origin",41.66666666666666],UNIT["Foot_US",0.3048006096012192]]

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