i.points.auto - GRASS GIS manual

NAME

i.points.auto - Generate ground control points for image group to be rectified.

KEYWORDS

SYNOPSIS

i.points.auto

i.points.auto --help

i.points.auto [-c] group=name source_image=name target_image=name [order=integer] npoints=integer [detail=string] [threshold=float] [--help] [--verbose] [--quiet] [--ui]

Flags:

-c: Use current region settings in source location instead of source map extends
--help: Print usage summary
--verbose: Verbose module output
--quiet: Quiet module output
--ui: Force launching GUI dialog

Parameters:

group=name [required]: Name of input imagery group
source_image=name [required]: Name of input raster map
target_image=name [required]: Name of input raster map
order=integer: Transformation polynom order (1-3); Options: 1, 2, 3; Default: 1
npoints=integer [required]: Maximum number of points to generate
detail=string: How detailed should the information be to be used.; Options: coarse, medium, fine; Default: fine
threshold=float: RMS error threshold. Recommended: source image resolution or smaller; Default: 0.0

DESCRIPTION
NOTES
SEE ALSO
AUTHORS

DESCRIPTION

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 (co-registration).

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.

AUTHORS

Ivan Michelazzi
Luca Miori
Markus Metz

SOURCE CODE

Available at: i.points.auto source code (history)