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NAME

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

KEYWORDS

imagery, ground control points

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

Table of contents

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. 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 Points Manager

AUTHORS

Ivan Michelazzi
Luca Miori
Markus Metz

Last changed: $Date: 2016-03-21 07:13:44 +0100 (Mon, 21 Mar 2016) $

SOURCE CODE

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


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