[postgis-users] Affine transformations of GIS data.

[Frank Durstewitz]

Good news, Bruce!

I will use this with googlemaps and ajax. Best case for me would be to 
be without additional table, but to give 2 collection of points (one 
with the "bad", one with the "good" coordinates) and simply return the 
coefs for use with ST_Affine.

Regards, Frank

Bruce Rindahl schrieb:
> 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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> 

-- 

Mit freundlichen Gruessen / kind regards

Frank Durstewitz

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