DESCRIPTION
i.points.auto tries to automatically generate a given number
of new gound control points (GCPs) by matching the input map to a target
map through FFT correlation. The goal of this computation is thus to
enable automatic geocoding of imagery to a master image.
NOTES
It is recommended to use maps filtered with the DIVERSITY or STDDEV filters
of the r.neighbors module, with a window size of 3x3 or 5x5
pixels. However, the algorithm sometimes works well also with the
original maps. The produced GCPs can then be used on the original imagery.
The actual number of newly generated ground control points will likely
be less than the given maximum number of ground control points because
each generated point is filtered using its FFT correlation
coefficient, and optionally also by the given RMS threshold.
i.points.auto supports the usual transformation orders 1-3 and
requires the corresponding number of previously set ground control
points: 3 for order 1, 6 for order 2, 10 for order 3.
SEE ALSO
The GRASS 4
Image
Processing manual
i.group
i.rectify
i.target
r.neighbors
Ground Control Point Manager
AUTHORS
Ivan Michelazzi
Luca Miori
Markus Metz
Last changed: $Date$