A RASTER SCAN CARTOGRAPHIC DIGITIZING SYSTEM
Robertson, Philip Keith
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The increasing demand for cartographic data in a digital form has resulted in a need for a low cost digitization system capable of rapidly digitizing large binary image areas. In the past, cartographic data has for the most part been digitally represented in vector form. However, the advent of powerful image display and processing devices, and the generation of large amounts of raster scanned data from sources such ad Landsat, have made the digitizing, handling and storing of data in raster form attractive. This thesis proposes a digitizing system based on a mini-computer controlled flat bed flying spot scanner. Map sheet can be digitized in binary form at a resolution of .004", with additional facility for the detection of lines as narrow as .002". Scanning a 30" x 30" map sheet takes approximately 10 minutes: the raster data is passed to the mini-computer (a PDP 11/60) where it can be further processed if required. A simple run length coding scheme, based on the statistical nature of raster represented map sheets, compact the date into a form suitable for storage.