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| GeoCommunity Mailing List |
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| Mailing List Archives |
| Subject: | Re: [gislist] Georeferencing Software |
| Date: |
03/01/2005 09:05:01 AM |
| From: |
Frank Warmerdam |
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On Tue, 1 Mar 2005 15:27:58 +0800, Runel T <rbtaningco@gmail.com> wrote:
> Is there freeware that can be used to georeference images?
Runel,
I think it might be helpful if you could be more specific about your
requirements. I am not formally trained in the geospatial field, but to
me to "georeference images" can mean a number of processes that
end up with an image that has an association between image locations
and real-world locations.
The simpliest case might be an already rectified image to which you
just want to attach georeferencing information by supplying the top
left, and bottom right corner coordinates along with a coordinate system
definition.
A more complex case might be supplying a bunch of ground control
points on the image, and wanting to rectify the image based on them.
Even more complex would be orthorectification where you want to
correct for sensor(camera) distortion and terrain effects.
There are also issues of how you want to collect your control
information. If you already have control information in a text file
then you just need to do the processing. But if you need an
interactive application to help you collect control information
(via image to image tiedown for instance) then that affects what
would be suitable.
Give a more detailed explanation of what you want, I am sure
folks can present you a number of options.
Without knowing more, some options include:
o My "gdal_translate" utility can be used to associate georeferencing
and a coordinate system with an existing rectified image. It is
available as part of FWTools.
http://fwtools.maptools.org/
o GRASS includes a variety of image rectification capabilities, including
(I think) orthorectification.
http://grass.itc.it/
o My "gdalwarp" utility includes the ability to do polynomial, and thin plate
spline based rectification of images based on a set of control points.
However, you would need to provide the control points on the command
line. GDAL includes no nice application for collecting control points.
I'm sure there are other options as well. You might want to browse
around on http://www.freegis.org/ for a while to see some other options.
Best regards,
--
---------------------------------------+--------------------------------------
I set the clouds in motion - turn up | Frank Warmerdam, warmerdam@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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