User Manual - pancroma

scans of the exact same patch of the earth's surface (these are called scenes).This legacy data can be used to fill in the gaps in more current scans.PANCROMA TM has the necessary utilities to perform such gap-filling operations.Alternatively, current gapped Landsat data can be used to fill gaps if the gapsbetween the two images do not exactly coincide.The gap filling procedure requires a Landsat Reference image (the one you aretrying to correct and which has the gaps) and at least one corresponding Adjustimage (the one you will extract data from to fill the gaps in the Reference image.)The Adjust image is usually gap-free, but it does not have to be. Because thegaps in two images may not coincide exactly, at least some useful data may betransferred from the Adjust image to the Reference image despite possible gapsin both.There are some fundamental problems with a gap-filling strategy. The first isimage registration. In order to transfer data from one image to the next, the twoimages must match exactly. The corner latitudes and longitudes must match andthe number of rows and columns must be the same in the two images as aminimum. Constructing a set of such matched images is a vital part of the preprocessingwork that must be done before the gap filling can begin.Another problem is inconsistencies in lighting, season, snow cover and cloudcover between images. Two images of the same area, even when properlymatched, may differ so significantly in these properties as to make themunattractive for gap fill. Of course great changes can occur over time in urbanareas and deforestation may occur in remote areas. Other secondary factorssuch as radiance and color cast due to lighting and atmospheric effects are alsoimportant. However these can be somewhat corrected by PANCROMA TM .This procedure will describe the process for gap-filling a 30m resolution LandsatRGB image from three band files using PANCROMA TM . I have chosen an imageof southern New Zealand for this tutorial to illustrate the process for producing auseful gap filled image. Start the gap filling process by selecting and downloadingyour Reference (gapped) Landsat scene. Record the Reference image Path andRow numbers when you download the image. Download the blue, green and redbands of the Reference image.The next step is to select your Adjust image. An easy way to do this is to use theGLOVIS website as it archives many Landsat scenes of the same Path and Rownumber. After navigating to the site, select 'Landsat Archive' and 'Landsat 7 SLCon(1999-2003)' from the drop down menus. Click the 'View Images' button.When the Visualization Viewer screen appears, type the Path and Row numbersthat you recorded earlier into the text boxes provided. Now click the 'Prev. Scene'and 'Next Scene' buttons to browse through all of the available scenes at yourselected Path and Row numbers.321