Image processing
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Introduction
Satellite imagery and orthophotos (aerial photographs) are handled in GRASS as raster maps and specialized tasks are performed using the imagery (i.*) modules. All general operations are handled by the raster modules.
- A short introduction to image processing in GRASS 6
- Full GRASS 4.0 Image Processing manual (PDF, 47 pages)
- Imagery module help pages
- Data import is generally handled by the r.in.gdal module
Screenshots
- The imagery screenshots page
Importing
Satellite Data
Ocean Color
Sea Surface Temperature
Orthophotos
- See the i.ortho.photo modules
Georectification
- See the Georeferencing wiki page
- Tcl/Tk georectification tool is available from the File menu in the GUI.
- i.points, i.vpoints
- i.ortho.photo
A multi-band image may be grouped and georectified with a single set of ground control points. (i.group, i.target, i.rectify)
Clustering
- Where's that table describing this? From the GRASS book help??
- MN: yes
- i.class, i.cluster
Filtering
- i.fft, i.ifft, i.pca, r.mfilter, r.neighbors
Enhancement
- i.landsat.rgb
- i.fusion.brovey
- i.oif
Stereo anaglyphs
- see Stereo anaglyphs
Ideas collection for improving GRASS' Image processing capabilities
Below modules need some tuning before being added to GRASS 6. Volunteers welcome.
Spectral unmixing
- i.spec.unmix (source code)
Spectral angle mapping
- i.spec.sam (source code)
Geocoding
- i.points.auto: automated search of GCPs based on FFT correlation (as improved i.points)
- i.homography: geocoding with lines (instead of points) with homography (as improved i.points; it was formerly called i.linespoints)
- support splines from GDAL (see GRASS_AddOns#Imagery_add-ons)
Image classification
- pr: C code for classification problems
- GRASS implementation: i.pr.* source code is available here)
Stereo
This is stand-alone stereo modeling software (DEM extraction etc). Waits for integration into GRASS.
Lidar LAS format
LAS Tools by M. Isenburg: http://www.cs.unc.edu/~isenburg/lastools/
las2txt | r.in.xyz in=- fs=" "
(see r.in.xyz)
Improving the existing code
It might be sensible to merge the various image libraries:
- GRASS 6 standard libs:
- lib/imagery/: standard lib, in use (i.* except for i.points3, i.rectify3)
- imagery/i.ortho.photo/libes/: standard lib, in use (i.ortho.photo, photo.*)
- GRASS 5 (! only) image3 lib:
- lib/image3/: never finished improvement which integrated the standard lib and the ortho lib. Seems to provide also ortho rectification for satellite data (i.points3, i.rectify3)
- GRASS 5/6 image proc commands:
- merge of i.points, i.vpoints, i.points3
- merge of i.rectify and i.rectify3
- addition of new resampling algorithms such as bilinear, cubic convolution (take from r.proj or upcoming r.resamp.aggreg)
- add other warping methods (maybe thin splines from GDAL?)
- implement/finish linewise ortho-rectification of satellite data