Vegetation Classification and Mapping Project Report - USGS

Accuracy Assessment and Additional Map Classes
4.2 Results
4.2.1 Accuracy Assessment Samples
In 2006, 662 accuracy assessment locations
were sampled (fig. 10 ). Data from 630 of
these locations were used in the accuracy
assessment analysis. The team eliminated
32 accuracy assessment points from the
accuracy assessment analysis in cases
where the team did not fully understand
the source of the error. This occurred in
areas where the sampled point was closer
to the polygon boundary than the error
recorded by the GPS unit. The team was
not sure if the thematic error was due to
error in georeferencing or to error in the
vegetation map database. Also, points
were eliminated when the vegetation
type recorded did not match the species
information recorded.
4.2.2 Base Map Class Accuracy and
Summary Statistics
4.2.2.1 Accuracy
The overall accuracy of the 46 base map
classes was 40.6%; kappa index was
42.2% +/- 0.22. As the kappa index and
its standard error use only map classes
with both sample and corresponding
reference data, it is slightly greater than the
overall accuracy. The contingency table
for base map class accuracy is presented in
Appendix H1.
The nine land-use map classes were not
assessed (table 12) but the five landform
defined map classes were. Two of the
vegetated map classes were not assessed
for accuracy; each consisted of only one
polygon outside the park boundaries.
Three base map classes, Sand, Coyote
Willow Shrubland and Blue Sage Dwarfshrubland,
had both 100% user and
producer accuracy. Another six map
classes (table 12) met the 80% accuracy
standard for either the user or producer
accuracy but not both. Except for
producer accuracy for Barren Badlands
(87.5%), accuracy for the seven most
abundant map classes was less than 80%.
Figure 10. Location of 662 accuracy assessment points at Petrified Forest
National Park observed in 2006.
4.2.2.2 Summary Statistics
Seven base map classes individually
contributed 5% or more to the land cover
of the park (excluding environs); together
they constitute just over 77% of the total
park land cover (table 13). The most
abundant map classes were:
● New Mexico Saltbush / Galleta – Alkali
Sacaton Shrub Herbaceous Vegetation
(24.2%, fig. 11)
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