The use of low cost scanning data for land cover mapping in the west central Sahel

The use of low cost scanning techniques in association with image processing is considered for land use/land cover mapping in part of the Sahel. This paper describes variations in the use of a Sharp JX 320 colour scanner and associated software in capturing satellite diapositive imagery (at 1:1 000 000) and thematic map data on a PC with the aim of developing a method for using scanned data in a GIS system. Optimal image scanning was achieved using PC‐Quickscan II with the MTR set to strong and RGB lightness at 100%. Scanning at 300 dpi developed a dot (pixel) size representing 86.7m on the ground. Thematic map scanning was improved by using the Image‐In program and the black and white lineart format set with no colour controls or edge correction. The spatial resolution of the digitised maps was 173.4m. Generally scanning imagery was best achieved through PC‐Quickscan because no editing was required. Since editing thematic maps was essential because extraneous lines and shadow was picked up, Imag...