| Summary: | The thesis of this work is that individual tree crowns can be automatically recognized in monocular
high spatial resolution optical images of scenes containing boreal or cool temperate forests
in a leaved state. The thesis was advanced by developing and testing an automatic tree crown
recognition procedure that is based on a model of the image formation process at the scale of
an individual tree. This model provides a means of applying specific scene and image formation
knowledge to the recognition task. The procedure associates instances of a three-dimensional
shape description with locations in a scene image such that the descriptions estimate the visible
scene extent of tree crowns that existed at the corresponding scene locations when the image
was acquired. This provides an estimate of the average horizontal diameter of the vertical
projection of individual recognized tree crowns, and a basis for species classification.
This work makes a contribution to the overall effort to increase the level of automation in
forest type mapping. This work also introduces and demonstrates the use of a pre-defined image
model to support the manual acquisition of a sample of unmodelled tree crown image properties,
and the use of constraints related to the spatial relationships among multiple neighbouring
candidate recognition instances to resolve image interpretation conflicts.
The procedure was tested with a scene of mixed uneven-aged forests in which the trees
represent a wide variety of species, size, and growing conditions. The results were assessed
on the basis of ground reference data and compared to those produced by human interpreters.
The scene represented a greater level of difficulty than that which has been addressed by
previous attempts at automating the tree crown recognition task. The test results show that
the procedure was able to largely accommodate the variation represented by the test scene, but
that human interpreters were better able to accommodate irregularities in tree crown form and
irradiance that were caused by tight vertical and horizontal spacing of the crowns.
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