Thematic Accuracy Assessment Procedures. Version 2 - USGS

3. Train field observers (Subsection 3.2.1).
4. Field observers navigate to assigned sites (Subsections 3.2.3 and 3.2.4).
5. Field observers identify and record vegetation type at sites, primarily using field key, and
record site positions (Subsections 3.2.5 through 3.2.9).
6. Review field data for egregious errors.
7. Compile field positional and attribute data into a Geographic Information Systems format
and in PLOTS database.
ANALYSIS AND ESTIMATION (CHAPTER 4.0) STEPS
1. Label sites with both map class and field observation class (e.g. through a spatial join of
field observation sites (points) to mapped classes (polygons) in a GIS).
2. Cross-tabulate sample data and reference data (typically using a pivot table) to produce
raw contingency table (Section 4.3).
3. Calculate contingency table accuracy and confidence interval values (Sections 4.4 and
4.5)
4. Aggregate or adjust raw contingency table classes, as necessary (Section 4.6).
REPORTING (CHAPTER 5.0) STEPS
1. Write accuracy assessment report (or accuracy assessment sections of project report).
1.5 Validation and Accuracy Assessment for Small Parks
For smaller and less complex parks, the accuracy assessment may be employed as both a
validation and an accuracy assessment step. Validation is a process of more limited sampling
whose objective is to determine whether a final draft map meets an acceptably minimal threshold
in order to proceed to the thematic accuracy assessment of individual map classes (see Appendix
E of this guidance and http://science.nature.nps.gov/im/inventory/vg/index.cfm and for an
explanation of validation). The results of validation address primarily the immediate needs of the
map production team and project oversight team to evaluate the overall product before passing it
on to a more committing thematic accuracy assessment campaign. Accuracy assessment is a
process that seeks to determine the reliability of individual map classes and is primarily to
inform the map user. In the course of evaluating individual map classes, the accuracy assessment
will also provide a measure of overall map accuracy, although it has a high cost/benefit ratio for
the latter purpose. Smaller parks are those with a calculated accuracy assessment workload of
fewer than 150 observations, as determined by the sample size allocation procedures described in
this guidance (Subsection 2.5.2).
In this small park scenario, if the accuracy assessment also indicates a project-wide accuracy that
fulfills the requirements of the validation, no further field work is needed. If the accuracy
assessment results indicate that the project-wide accuracy is inadequate, then the results are
treated as a validation. The observations then may be used (“recycled”) as verification
observations (Table 1, Figure 1, and Appendix E of this guidance and
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