i.points.auto tries to automatically generate a given number
of new ground control points (GCPs) by matching the input map to a target
map through FFT correlation, based on a few existing ground control points,
previously defined by the user, for example through the
Ground Control Points Manager.
The goal of the module is thus to automaticallty increase the number of control
points to enable higher quality geocoding of imagery to a master image
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.
The GRASS 4
Ground Control Points Manager
Last changed: $Date$