User Manual - pancroma

Although the run was not successful in discriminating Lawn Grass, a fewconclusions can be drawn:• The method did seem to be a fairly sensitive discriminator for the plowedfields• More experimentation with the selection criteria might find the grassyfields as intended• The technique appears to be more sensitive and more positive than eitherfalse color composites or classification• It is clear why more multispectral bands are better, and why hyperspectraldata is the best for this purpose. It is also clear why 11 bit or 16 bit data isbetter than 8 bit data, as the former yields more resolving power forapplications like thisThe PANCROMA TM LSA is a powerful tool for exploring and characterizinggeological and agricultural aspects of the earth’s surface with many possibleuseful applications. However like most tools, it still relies on the expertise andskill of the user to produce the best results. This example showed how it ispossible to discriminate plowed fields in an image. Although this particular taskwas relatively simple, the method is equally applicable to cases where thediscrimination is not so obvious, as in mineral exploration.Landsat Reflectance Spectral Analyzer TMAs described above, the PANCROMA TM Spectral Analyzer TM can convertLandsat band file DNs to TOA reflectance and then compare the computedreflectance values to archived surface spectra. The USGS offers Landsat datasurface reflectance data. This information is archived in at least two formats. TheGlobal Land Cover Facility archives surface reflectance values in I16, LittleEndian format. GLOVIS archives the six multispectral bands in a single PlanarConfiguration=2 file. PANCROMA can decode both of these formats butcurrently the Spectral Analyzer TM can only process the individual bands archivedat GLCF. It uses the data in these files directly instead of computing TOAreflectance values from Landsat DNs.There are several advantages to using surface reflectance as an alternative toDNs or even computing TOA reflectances from DNs. Surface reflectance isbasically TOA reflectance corrected for atmospheric effects. As a result, surfacereflectance values are generally superior to TOA reflectance as removing theatmospheric effects makes them more similar to the archived spectra, as thesevalues are usually measured directly at the surface. Another advantage isprecision.The surface reflectance values are archived as 16-bit integers with a valid rangeof –2000 to 16000. A value of –9999 represents ‘no data’ while 20000 is‘saturation’. PANCROMA TM sets ‘no data’ and ‘saturation’ values equal to zeroand decodes the valid integers, scaling them by a factor of 0.000100 (in242