Error matrices based on the building object (polygon) were produced
for the two scenarios of the difference DEMs. Comparing
with the pixel-based assessment method that classifies the difference
DEM pixels into collapsed and not collapsed pixels by examining
the height change of the building that a pixel represents, the
advantage of the object-based assessment method is that the percentage
of difference DEM pixels that fall inside a building polygon
is used to determine whether a building has collapsed, which
might provide a more realistic accuracy assessment of the detection
of collapsed buildings.