User Manual - pancroma

For Landsat 7 data sets, the NIR band4 will be displayed for point selection asthe default. The NIR band often works better is because the excessive Rayleighscattering exhibited by the blue band can obscure surface details to such anextent that pixel selection is difficult. Let’s say that we are interested inmeasuring the snow pack coverage for the subsetted region in the image. Snowpack measurements are often needed in order to estimate the amount of runoff inthe spring and to determine the water supply potential for down gradient areas.We can estimate the coverage using the PSG, followed by using the LandsatSpectral Analyzer TM (see following section).We first start by opening either six Landsat visible and infrared multispectral bandfiles, or alternatively the six multispectral bands plus the thermal infrared (TIR)band 6. That is, either open bands 1,2,3,4,5 and 7 or alternatively bands 1, 2, 3,4, 5, 6 and 7 by selecting ‘File’ | ‘Open’ as usual. Next select ‘Spectral Analysis’ |‘Landsat Point Spectrum Generator’ | ‘Six/Seven DN Bands’. When you do so aband selection screen will be displayed. Note that there are two radio buttonslabeled ‘Display Single Band’ and ‘Display Color Composite’. This allows thechoice of using either a single multispectral band for point selection or acomposite of three bands. For this exercise select ‘Display Single Band’. Thecolor composite option will be explained at the end of the section.IMPORTANT NOTE: Using the TIR band may give additional discriminatingpower to your analysis. If you decide to use the TIR band, you may have topreprocess it before doing so. Some Landsat TIR files are archived the samesize as the multispectral band files. However most are archived as 57 or 60mresolution files, i.e. half the resolution of the multispectral bands. In addition,there are usually two TIR band files with suffixes 61a and 61b. These are thehigh gain and low gain versions of the data. If you choose to use the TIR band,you will be prompted to tell PANCROMA which type of file you are processing bychecking a radio button on the TOA Reflectance Form.In order to use a TIR band at half resolution, you must first expand andinterpolate it up to 27.5 or 30m resolution. This can be done using the utilitydescribed in the Preprocessing Section. Once the scale is adjusted, it can beused to generate a Point Spectrum.When PANCROMA TM processes the TIR band, it will divide the computedtemperature in degrees Kelvin by a factor of 1000. This scales the temperaturedata so that it is of the same order of magnitude as the TOA reflectance data.You can select the multispectral band that you want to be displayed for pointselection by checking the appropriate radio button.221