[postgis-users] Affine transformations of GIS data.

[Bruce Rindahl]

Anyone interested in this can follow progress off-line at:
http://casoilresource.lawr.ucdavis.edu/drupal/node/532
Thanks!
Bruce Rindahl

-----Original Message-----
From: postgis-users-bounces at postgis.refractions.net
[mailto:postgis-users-bounces at postgis.refractions.net] On Behalf Of Bruce
Rindahl
Sent: Thursday, January 24, 2008 4:31 PM
To: 'PostGIS Users Discussion'
Subject: [postgis-users] Affine transformations of GIS data.

Based on a previous post on affine transformations of GIS data in PostGIS, I
have put together a function that takes a table of control points and
computes the affine transformation coefficients using the least squares code
from GRASS.  A nice tutorial by Dylan Beaudette on this is at:
http://casoilresource.lawr.ucdavis.edu/drupal/node/433

At this point I would like some feed back on how this could be used.  I
envision a GIS package (say uDIG) would allow a user to select pairs of
points and populate a table with a similar layout as ESRI's link table when
georeferencing.  A query would give the RMS error and similar query would
return the table back with the residual errors. If the user were then happy
with the values (after deleting poor matching points), a final query could
then be made to the ST_Affine function to modify the geometry based on the
control points.

Comments?

Bruce Rindahl


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