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
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.
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
Image
Processing manual
i.group
i.rectify
i.target
r.neighbors
Ground Control Points Manager
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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GRASS Development Team,
GRASS GIS 7.4.1svn Reference Manual