2.8. Performance of the classification algorithm
The classification accuracy was assessed using pixel-wise and
polygon-wise overall accuracy (OA) that were calculated for each
PT. The pixel-wise OA is the number of correctly classified pixels
divided by the number of classified pixels. Polygon-wise OA is
the number of correctly classified polygons divided by the number
of classified polygons. A polygon was considered correctly classi-
fied if a majority of the pixels within the polygon was classified in
the same class as that polygons class. A polygon was considered
classified if a majority of its pixels were classified into some of the
target classes. Non-vegetation pixels were excluded from the calculations.
The percentage of unclassified vegetation pixels in the
image was calculated by dividing the number of unclassified pixels
in the image by the total number of pixels in image, while the number of non-vegetation pixels was excluded. The percentage of
unclassified pixels within target and non-target polygons was calculated
similarly, with the additional exclusion of shadow polygons
and pixels. Additionally, the percentage of unclassified target and
non-target polygons were calculated. Omission and commission
errors were studied for selected classifications.