[Gdal-dev] Image Reprojection

[Matt Lynch]

Hi Frank,

The gdalwarptest sounds interesting.  To get an orientation I have built
GDAL (the cleanest open source build on a windows box in a long time, by
the way!). 

When I try to run gdalwarp I just get a usage blurb.
------------------------------------------------------------------------
-----------------
C:\gdal>gdalwarp -t_srs '+proj=latlong +datum=WGS84' jeffpan2000_10m.tif
out.tif

Usage: gdalwarp [--version] [--formats]
    [-s_srs srs_def] [-t_srs srs_def] [-order n] [-et err_threshold]
    [-te xmin ymin xmax ymax] [-tr xres yres] [-ts width height]
    [-of format] [-co "NAME=VALUE"]* srcfile dstfile
------------------------------------------------------------------------
-----------------

jeffpan2000_10m.tif is in the current directory
out.tif does not exist yet.


The details of jeffpan2000_10m.tif are below
------------------------------------------------------------------------
-----------------
C:\gdal>gdalinfo jeffpan2000_10m.tif
Driver: GTiff/GeoTIFF
Size is 2000, 2000
Coordinate System is `'
Origin = (644995.948217,5518006.066294)
Pixel Size = (10.000000,-10.000000)
Metadata:
  TIFFTAG_DOCUMENTNAME=jeffpan2000_10m.tif
  TIFFTAG_SOFTWARE=ImageMagick 5.5.2 12/01/02 Q8
http://www.imagemagick.org
Corner Coordinates:
Upper Left  (  644995.948, 5518006.066)
Lower Left  (  644995.948, 5498006.066)
Upper Right (  664995.948, 5518006.066)
Lower Right (  664995.948, 5498006.066)
Center      (  654995.948, 5508006.066)
Band 1 Block=2000x4 Type=Byte, ColorInterp=Gray
------------------------------------------------------------------------
-----------------

Have I got the syntax wrong?  Or is it because the image is in 10TM
which is not recognized?

Thanks,

Matt


-----Original Message-----
From: gdal-dev-admin at remotesensing.org
[mailto:gdal-dev-admin at remotesensing.org] On Behalf Of Frank Warmerdam
Sent: Thursday, April 03, 2003 7:56 AM
To: gdal-dev at remotesensing.org
Subject: Re: [Gdal-dev] Image Reprojection


Matt Lynch wrote:
> Hi,
> 
> I am interested in writing or using a windows command line utility 
> which will reproject GeoTiffs for me.  It seems that the gdalwarp 
> utility is what I want.
> 
> So I have a couple of questions ...
> 
> 1.  Am I correct that gdalwarp will reproject GeoTiffs for me?  (e.g. 
> UTM to Decimal Degrees) 2.  Are there some usage examples that I can 
> refer to?

Matt,

I trust you have read the modest docs at:

   http://www.remotesensing.org/gdal/gdal_utilities.html#gdalwarp

Yes, it can reproject GeoTIFF files from UTM to decimal degrees.   The
only
example is the one in the documentation.  To do what you want you might
use:

  gdalwarp -t_srs '+proj=latlong +datum=WGS84' in.tif out.tif

Note, there is also a "gdalwarptest" in the CVS version of GDAL with
similar commandline options as gdalwarp, but using a much more
sophisticated approach internally.  In particular, it:
  o Supports a all pixel types, not just 8bit like gdalwarp.
  o Will work on images that cannot be held completely in memory.
  o Supports a variety of resamplig kernels.
  o Has "NODATA" support.

Gdalwarptest is the "test harnass" for this next generation warper.
Depending on your needs I would appreciate help in testing this new
implementation.

Best regards,
-- 
---------------------------------------+--------------------------------
---------------------------------------+------
I set the clouds in motion - turn up   | Frank Warmerdam,
warmerdam at pobox.com
light and sound - activate the windows | http://pobox.com/~warmerdam
and watch the world go round - Rush    | Geospatial Programmer for Rent


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