A digitizer (Figure 8-11) is similar to a planimeter
, except that it is an electronic instrument that automatically transmits measurements from blueprints into software estimating programs (provided you have the necessary software interface).
By the Thiessen Polygon method, the areas represented by the polygons surrounding each rain gauge are determined with a planimeter
and substituted in Equation 3.1:
The change in bank location is traced onto each aerial photograph and then the area of change is measured using an electronic planimeter
. This procedure provides the change in surface hectares, which is multiplied by the surveyed bank height to calculate the cubic vards of soil loss.
Strata areas were measured from nautical charts with a digital planimeter
Working with tools such as the scale, protractor, triangle, planimeter
, calculator, graph paper, and/or the computer, the estimator counts, measures, and calculates every item needed for the landscape and every minute of time required as labor.
Catchment area was measured with a digital planimeter
on 1: 10 000 orthophoto maps.
Square km of occupied range were then determined using a compensating polar planimeter
If dimensions aren't marked on the drawings, the estimator uses scale rules or a planimeter
to estimate the size of the various portions of the job (e.g., the total size of the lawn area for sodding).
Estimates of group areas were compared with areas from 30 groups plotted on an aerial photograph and measured with a compensating polar planimeter
; values generated by those 2 techniques did not differ by > 10%.
Research in ascertaining the accuracy of the land use/land cover data on the MRPI involved a comparison with data found on 1938 SCS aerial photographs (USDA 1938) from the Center for Remote Sensing, Aerial Photograph Archive, Michigan State University, East Lansing, Michigan, using planimeter
So we measured initial and fin al gallery widths with digital calipers, measured the lengths with a digital planimeter
after tracing the galleries on clear mylar, and estimated gallery size as the area of a trapezoid of these dimensions.