Vegetation Classification and Mapping Project Report - USGS

Base Map Class Development
overlay as the work area for the photo.
Fiducial marks (representing a fixed
basis of reference) were transferred to
each transparent polyester sheet, along
with the park code and photo number. A
stereoscope was used to help distinquish
topographic features with elevational
differences and details of photo signatures.
Each photo of the northern section and
every other photo of the southern section
was interpreted, and every other photo
of the southern section. This decision
was based on the preferences of each
photointerpreter after ensuring that
joining the northern and southern sets of
transparent polyester sheets would not
create problems in the final map.
The ground reference data for
photointerpretation was supplied by
the field reconnaissance observations,
classification relevés, and the 1996
sampling data. Cully and McTeague
developed a list of provisional base
map classes that represented the plant
communities as seen in the aerial
photography. They labeled the polygons
using known and interpreted relationships
among the photo signatures, the ground
reference data, and the provisional base
map classes. Adjustments were made to
the provisional base map classes and to
the plant community classification during
this phase of the project. Adjustments
consisted of
● adding map classes to the land use
classification, based on observations
during field reconnaissance
● including unique stands of plant communities
into existing map classes
● expanding provisional map class concepts
to include field observed plant
communities
Cully and McTeague identified each
delineated map class with a numeric
code referencing its provisional map class
assignment and any modifiers applicable
to the polygon. The modifiers, developed
in coordination with the Northern
Figure 8. Location of photointerpreters’ observation points at Petrified
Forest National Park.
Colorado Plateau Network (NCPN),
indicated vegetation density (in percentage
categories), pattern, and height (table
6) and were applied to the uppermost
stratum of each plant community. The
height modifier described the average
height of the plant community represented
by the polygon. A modifier was also used
to describe the environmental condition
surrounding the vegetation. Cully
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