Dylan Beaudette wrote:
I have a problematic TIGER module - i.e. a single county in Ca is really
messed up. I thought that a simple translate() would do the job, but it looks
like there is both a translation and rotation involved. I do not really
understand the postgis manual entry for the affine function.
How would one go about converting a series of coordinate pairs ([good], [bad])
into the terms of the affine transform matrix?
thanks,
Dylan,
You will have a secondary problem if you apply an affine function ot
otherwise transform the county in that TIGER is topologically correct
even is the interior segments are out of place.
If you trans form it you might better align the segments on the interior
but you will disconnect the roads from the road network at the county
boundaries. If you are only displaying on county and not the adjacent
counties then this might not matter too much. Otherwise you can expect
to get discontinuities of segments the cross the county boundaries.
Some GIS programs support transforming a network of segments by
providing anchor points and vertices to move, and then transform based
on linear or bicubic transforms built on these control points for the
other points in the network. Someone with GRASS knowledge might be able
to tell you if GRASS can do this.
-Steve
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