New and Improved Procedure for Minimum DN Selection
for input to the COST Model for Atmospheric Correction
K.Mauz, 1/9/2002The motivation behind this improvement lies with the observation of the "halo" of low DN values around the perimeter of TM scenes. The procedure described here allows you to choose minimum DNs that are actually in the scene. It is also much simpler, faster, and more parsimonious than eyeballing the histogram, the old method for minimum DN selection. The new method facilitates consistency between images and between analysts in the selection of minimum DN values.
1. Open one band in the image in PseudoColor mode in ERDAS Imagine.
2. Open Raster Attributes.
3. Color the low DNs until you see colored pixels show up in the scene. The DN value of the first pixels to show up is your minimum DN for that band.
4. Repeat for the other bands.The screen capture below illustrates the steps in the procedure. You can see the halo of low-DN pixels around the scene, colored yellow, and the first pixels actually in the scene (indicated by the arrows). The minimum DN value for this band would be 33 as indicated in the Raster Attributes Editor table (highlighted row).
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Arizona Remote Sensing Center, Office of Arid
Lands Studies, Last updated: 3 December 2002 |