The areas were measured by first determining the planimeter constant. The constant was determined by measuring a square area of 4 in2. Three readings were taken that varied by only 0.002 units. These three measurements were averaged, and a constant of 13.730 calculated. Following this procedure, a circle of area 4 in2 was measured three times and the average of these readings calculated. For the circle, an average constant of 13.029 was calculated. The final step in determining the overall planimeter constant was by averaging these two constants. In this way, both straight lines and curved lines are taken into account in the calculation of area. The final averaged planimeter constant was 13.380.
The perimeter and longest flow path length were determined using a map
Similar to measurements taken with the planimeter, each area
measured three times, and the average measurement taken.
calculated by subtracting the elevation of the longest flow path at the outlet of the subbasin from the elevation at the start of the longest flow path, divided by the length of the longest flow path. Table 4.1 outlines the results of each calculation for area, perimeter, longest flow path, and slope as derived by traditional methods.
Table 4.1: Hand Delineation Results
Longest Flow Path (mi) 1.69 3.14 6.28
Slope (%) 1.27 1.47 0.77