Image processing

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Revision as of 09:28, 1 April 2008 by ⚠️HamishBowman (talk | contribs) (MODIS)
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This page needs review and enhancement from an expert! Thanks!

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.

  • Data import is generally handled by the r.in.gdal module


Screenshots

Georectification

  • 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

Satellite Data

MODIS Aqua

SST (Level 3)

Chlorophyll-a (Level 3)

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

Spectral angle mapping

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

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