Figure 3.6: Map Wheel
3.2.3 Parameter Extraction
Using traditional methods, hydrologic parameters are extracted from paper
elevations from the upper point of the longest
on the difference in contour flow path and from the outlet.
difference in elevation is divided and longest flow path length are calculated using the planimeter.
by the length of the longest flow path. Perimeter determined by using the map wheel, and area is
CASE II: ON-SCREEN DIGITIZING OF RASTER GRAPHIC MAPS
The process of on-screen digitizing of raster graphic maps is the next
closest method to the traditional, paper map based methods of using a map wheel
and a planimeter. The methodology is analogous; with the exception that the