Vegetation Classification and Mapping Project Report - the USGS

Figure 20. A portion of the GRSM understory density data set depicting light, medium and
heavy densities of Rhododendron (R), Kalmia (K) and mixed Rhododendron/Kalmia (RK).
Conclusion
Experience gained from conducting this five-year study to develop detailed overstory and
understory vegetation, fire fuel model and leaf-on and leaf-off percent canopy cover databases
for GRSM can be used to make recommendations on the best source materials and procedures
for mapping vegetation in remote and mountainous areas. First, there should be careful
consideration of the aerial photographs or image data source to insure a high level of detail in
identifying vegetation composition is balanced with photogrammetric and mapping
requirements. The construction of vegetation databases over extensive areas of mountainous
terrain should focus on the acquisition and use of aerial images recorded by a standard 23 x 23
cm format photogrammetric film camera system (or the newer digital photogrammetric cameras)
equipped with a lens of not less than 15 cm focal length and, preferably, 30.5 cm. While this
longer focal length camera necessitates an aircraft operating at higher altitudes for a given scale
or pixel resolution, the greater flying height significantly reduces displacements due to terrain
relief – a most serious problem when attempting to create detailed GIS databases from large
numbers of aerial photographs. Furthermore, if at all possible, the camera system should be
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