[Proj] Rectification of maps

Clifford J Mugnier cjmce at lsu.edu
Thu Sep 22 13:04:25 EDT 2005

On 9/22/05, Thomas Flemming <tf at ttqv.com> wrote:
> Hello,
> I often have maps with unknown projection information but printed lat/lon
> grids. Or papermaps, which have strong deformations so that after
scanning the
> projection does not fit anymore.
> Is there a way in proj to calculate x-y/lat-lon by defining a couple of
> referencepoints ?


It seems like what you would want is a rubber sheeting transform
of some kind based on a bunch of reference points.  Two reference
points wouldn't give you much information.  PROJ.4 does not
address this issue.  I do have such a capability in GDAL -
underlying transformations based on reference points and a way
of applying it to resample rasters.

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


I would recommend an eight-parameter projective transformation based on
four points of a graticule.  The panelling of such is identical to the old
graphical technique employed by cartographers of 20 years ago.

Cliff Mugnier

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