Interpolating Measure Data
In interpolating measure data, the area of the source polygon is irrelevant, but the area of the target polygon is used to arrive at the target value.
For measure data, the value for each target polygon is estimated by converting the measure values to their equivalent count values for each target/source intersection. These values are summed for each target polygon, and then converted back to a measure value by dividing by the area of the target polygon.
Vt = ( Σ Vs * Ats ) / At
Vt = value of the target polygon
Vs = value of the source polygon
Ats = area of the intersection of the target and source polygons
At = area of the target polygon
Non-areal proportions require special treatment.
Consider the following coverages:
Assuming As Ats and Vs shown below, PARS calculates Vt as follows:
|Vs * Ats
(m * ha)
Source: modified from Ballard and Schut, 1995
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