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MEMO 93 <br /> <br />~+ <br />u~"_611~ <br />~'~~~ ~ ~ ~ <br /> <br />- .~ _ ~'~• <br />u <br />F <br /> <br /> <br /> <br />,y <br />ry ~ . f <br />JE ~rik ~.. ~~ <br />i G <br />~~~ 1 <br />S q <br />e <br />~ ~ <br />f7" .- ~'~' <br />~ t~ ~ <br /> •~ ~ <br /> <br />t'NJ * - <br />~'dF ~ <br />~~~. <br />~~ <br /> <br /> <br /> <br /> ' <br />^ ~ <br /> ~ <br />~ J <br /> =~S: r ~. <br />(a) Landsat TM -Frame 33/32: <br />July 1, 1987 <br />(b) Landsat MSS -Frame 36/32: <br />July 12, 1976 <br />(c) Aerial Index -Manual mosaic of aerial photo prints: <br />June-August, 1956 <br />Figure 2. Example of imagery in Larimer County (a) Landsat TM, (b) Landsat MSS, (c) aerial index, <br />displayed at 1:52,000 scale. <br />2.2 Radiometric Correction <br />Pixel values in commercially available satellites are calibrated to fit a certain range of radiance values of <br />the earth surface in the form of Digital Numbers (DN). Since each sensor has its own calibration <br />parameters used in recording the DN values, the same DN values in two images taken by two different <br />sensors may represent two different radiance values. In order to compare and analyze images taken by <br />different sensors (e.g., Landsat 1-4 MSS versus Landsat 5 TM), it was necessary to convert the DN values <br />to absolute radiance values. Radiometric correction of Landsat TM and MSS imagery followed <br />procedures described in SPDSS Technical Memorandum 89.2. Adaptations were made for radiometric <br />correction of Landsat MSS imagery (Chavez, 1996). <br />Page 4 of 59 tij,Rarera~de ~eshn~f~gy, loss <br />