Groundtruthing of vegetation cover is unreliable for features with large areas
(>1000 m2 or length >100 m) and inconsistent management or variable vegetation
cover. Even when their area is < 1000 m2, many of these features have
elongated or complex shapes that spread over so large an area that the “typical”
vegetation cover of the feature is very difficult to identify consistently, even
using groundtruthing. To enhance the repeatability of feature classification by
groundtruthing, large features should be broken into smaller, simpler components
prior to groundtruthing.
- The goal of feature cutting is to divide features with area > 1000 m2
into smaller parts (<1000 m2) amenable to groundtruthing,
using as few cuts as possible. By minimizing the number of cuts and
features created by cutting, inconsistencies in mapping and classification are
- Select large Disturbed features using Select by Attributes, with
the expression: “USE = D AND area >1000”. Select large Ornamental
features using “USE = O AND area >1000”
- IF the feature consists of areal and linear parts:
- IF any part of a >1000 m2 Disturbed or Ornamental
feature has narrow areas with width <10m, then the feature may be cut
into two or more parts at these narrow areas. Choose the narrowest parts of the
feature as the place to cut.
- Features with an areal part attached to a linear part: cut this into two pieces, one areal, one linear.
- Features with an areal part and more than one linear part: cut off the linear parts, starting with the longest, leaving an areal part and several linear parts.
- IF the feature is elongated (mostly linear) and has no areas that are
significantly narrower or wider than others, THEN start at the NORTH or WEST end
of the feature and cut it into sections that are approximately 100 m long.
- IF there are clear linear features within large areal features (in the image and
on the ground), even if they are <2 m (too small to map at L1), these features
can be used to draw a line and used to clip the Disturbed or
Ornamental feature into smaller pieces.
- STOP cutting the features AS SOON AS each feature has: area <1500 m2
AND length <100 m.