Geoscience Reference
In-Depth Information
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RESOLUTION 2
RESOLUTION 3
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RESOLUTION 6
RESOLUTION 12
Figure 17.6 Map REF at four different resolutions. On the legend, 0 means completely forest, 1 means
completely nonforest, and white is outside of the study area.
is taken into consideration by the weights that give each cell's membership in the study area. This
characteristic of the technique allows the method to apply to accuracy assessment where the grid
cells of interest are not contiguous.
Figure 17.5 shows the cell configuration. The darker shading shows stronger membership in
the nonforested category. Figure 17.6 shows this same type of aggregation for the REF map. For
each resolution, we are able to generate a bar similar to the nested bar of Figure 17.4, because the
equations of Figure 17.3 allow for any cell to have partial membership in any category.
17.3 RESULTS
Figure 17.7 shows the components of agreement and disagreement between REF and COM1
at all resolutions. Figure 17.8 shows analogous results for the comparison between REF and COM2.
The overall proportion correct is the top of the component of agreement at the grid cell level and
the overall proportion correct at the coarser resolutions is the top of the component of agreement
due to quantity. Proportion correct tends to rise as resolution becomes coarser; however, the rise
is not monotonic. Proportion correct rises for each resolution that is nested within finer resolutions.
That is, the proportion correct for resolution 1 < proportion correct for resolution 2 < proportion
correct for resolution 6 < proportion correct for resolution 12. In addition, the proportion correct
for resolution 1 < proportion correct for resolution 3 < proportion correct for resolution 6 <
proportion correct for resolution 12. However, the proportion correct for resolution 2 > proportion
correct for resolution 3. Note that resolution 2 is not nested within resolution 3.
The largest component is agreement due to chance, which is 50% at the finest resolution since
there are two categories. Agreement due to chance rises as resolution becomes coarser. Besides the
component due to chance, the largest components at the finest resolution are agreement at the grid
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