6.13 Tasseled Cap Transformation

Tasseled Cap Transformation (TCT) is a useful tool for analyzing physical ground features using remotely sensed imagery.

With various Landsat imagery, it uses 5 bands of either original digital number (DN) or reflectance data to generate 6 new bands, each of which represents different ground features. The 6 resulting bands are generally called (soil) brightness, (vegetation) greenness, (soil and canopy) wetness, haze, TC5, and TC6. Each one or a combination of them is useful for different applications, such as crop growth monitoring and analysis, biomass study, and agriculture planning.

Example 6-15 Tasseled Cap Transformation

Example 6-15 takes the DN data of a Landsat 5 TM image as input, executes the TCT using the GeoRaster raster algebra with parallelism, and creates a new image holding the results.

DECLARE
    gr1 sdo_georaster;
    gr2 sdo_georaster;
    ret varchar2(32);
BEGIN
    select georaster into gr1 from georaster_table where georid = 2;
    select georaster into gr2 from georaster_table where georid = 4 for update;
    sdo_geor_ra.rasterMathOp(
      gr1,
      SDO_STRING2_ARRAY(
         '0.3561*{0}+0.3972*{1}+0.3904*{2}+0.6966*{3}+0.2286*{4}+0.1596*{6}',
         '(-0.3344)*{0}-0.3544*{1}-0.4556*{2}+0.6966*{3}-0.0242*{4}-0.2630*{6}',
         '0.2626*{0}+0.2141*{1}+0.0926*{2}+0.0656*{3}-0.7629*{4}-0.5388*{6}',
         '0.0805*{0}-0.0498*{1}+0.1950*{2}-0.1327*{3}+0.5752*{4}-0.7775*{6}',
         '(-0.7252)*{0}-0.0202*{1}+0.6683*{2}+0.0631*{3}-0.1494*{4}-0.0274*{6}',
         '0.4000*{0}-0.8172*{1}+0.3832*{2}+0.0602*{3}-0.1095*{4}+0.0985*{6}' ),
      'celldepth=32BIT_REAL',
      gr2, null, null, ‘parallel=4’); 
    update georaster_table set georaster = gr2 where georid = 4;
    commit;
END;
/

You can also use the same raster algebra language to add code in Example 6-15 to convert the 32-bit floating number image into an 8-bit integer image and to apply image stretching (described in Image Stretching) on the resulting TCT image to generate a new GeoRaster object for visualization and analysis.

In addition to using the optimized implementation of raster algebra algorithms and the embedded parallel processing, you can further take advantage of the Oracle grid computing infrastructure to quickly compute NDVI or apply TCT on thousands of images stored in the GeoRaster database.