Introduction to Radar data processing

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2010年1月28日 (木) 20:55時点におけるNeteler (トーク | 投稿記録)による版

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Introduction to Radar data processing

Sensors

SAR analysis methods

  • SAR backscatter analysis (about): enables to estimate volume of water contained in soil, volume of biomass in forests, conditions of waves in the ocean etc.
    • Requirements: ...
  • SAR interferometry processing (about): enables to produce elevation data and to measure topographical change (two SAR images are used - called Master Image and Slave image, respectively)
    • Requirements: complex SAR data - Single Look Complex as parallax is not removed
    • General steps (cited from CCRS tutorial):
      • Process data to SLC images
      • Register the two images to 1/10 pixel
      • Over-sample by a factor of 2 in both dimensions
      • Filter common bands in spectrum
      • Conjugate multiply to form interferogram
      • Smooth the interferogram
      • Measure coherence
      • Unwrap phase
      • Estimate geometry parameters (especially baseline)
      • Remove flat-earth fringes
      • Convert unwrapped phase to height and/or motion
  • Polarimetric SAR processing (about): forest fire monitoring, classification of vegetation (height), water content in vegetation, monitoring of snow cover, condition of ice, flood monitoring and soil moisture.
    • Requirements: ...

Frequency and Wavelength of the IEEE Radar Band designation

Frequency [GHz] Wavelength [mm] Band
1-2 30-15 L Band
2-4 15-75 S Band
4-8 75-375 C Band
8-12 375-250 X Band
12-18 250-167 Ku Band
18-27 167-111 K Band
27-40 111-0.75 Ka Band

Software installation

Windows:

Linux:

    idl -vm=rat.sav

Radartools usage on PALSAR

  1. File -> open external -> ALOS-PALSAR (ERSDAC CEOS) -> PASL1500911220116591001270049_ortho.dat
  2. Try to zoom Mount Fuji

This is an orthorectified SAR image, i.e. that no interferometry can be performed.

Exercises: Speckle filtering (see SAR -> Wizard mode), color table adjustments, etc.

GRASS GIS usage on PALSAR

First we need to rewarp the .dat format to GeoTIFF which also applies the included Ground Control Points (GCPs) to the image. The resulting GeoTIFF file is then geocoded in Lat-Long/WGS84:

  1. gdalinfo PASL1500911220116591001270049_ortho.dat
  2. gdalwarp PASL1500911220116591001270049_ortho.dat PASL1500911220116591001270049_ortho.tif

Now we can auto-generate a GRASS Location from the GeoTIFF:

  1. Start 'grass64 -wx' or from menu (graphical user interface)
  2. Select Location Wizard
  3. Define a good name for the Location, then Next
  4. Select the item "Read projection and datum terms from a georeferenced file", then select the newly created PASL1500911220116591001270049_ortho.tif file, Next.
  5. Now the location is generated and the region is set to the image dimensions (degree in this case)
  6. You will return to the GRASS entry screen and can open the new location. Still the data have to be imported.

When in GRASS, import the map and display it:

  1. import with File -> Import raster map -> Import raster data using GDAL -> Select again PASL1500911220116591001270049_ortho.tif and define name for this map in GRASS, when finished close dialog window
  2. Add map to map tree in the layer manager, using the icon Add raster map layer. It should be automatically displayed
  3. Use the zoom tool Zoom in in the map display manager to zoom Mount Fuji
  4. You will not recognize much yet since a better color map has to be assigned

Sample data

See also