Geoscience Reference
In-Depth Information
2
CHAPTER
Sampling Design for Accuracy Assessment
of Large-Area, Land-Cover Maps:
Challenges and Future Directions
Stephen V. Stehman
CONTENTS
2.1 Introduction.............................................................................................................................13
2.2 Meeting the Challenge of Cost-Effective Sampling Design .................................................15
2.2.1 Strata vs. Clusters: The Cost vs. Precision Paradox .................................................15
2.2.2 Flexibility of the NLCD Design ................................................................................16
2.2.3 Comparison of the Three Options..............................................................................17
2.2.4 Stratification and Local Spatial Control ....................................................................18
2.3 Existing Data ..........................................................................................................................21
2.3.1 Added-Value Uses of Accuracy Assessment Data.....................................................21
2.4 Nonprobability Sampling .......................................................................................................22
2.4.1 Policy Aspects of Probability vs. Nonprobability Sampling.....................................23
2.5 Statistical Computing .............................................................................................................23
2.6 Practical Realities of Sampling Design .................................................................................24
2.6.1 Principle 1...................................................................................................................24
2.6.2 Principle 2...................................................................................................................24
2.6.3 Principle 3...................................................................................................................25
2.6.4 Principle 4...................................................................................................................25
2.7 Discussion...............................................................................................................................25
2.8 Summary.................................................................................................................................26
References ........................................................................................................................................27
2.1 INTRODUCTION
This chapter focuses on the application of accuracy assessment as a final stage in the evaluation
of the thematic quality of a land-cover (LC) map covering a large region such as a state or province,
country, or continent. The map is assumed to be classified according to a crisp or hard classification
scheme, as opposed to a fuzzy classification scheme (Foody, 1999). The standard protocol for
accuracy assessment is to compare the map LC label to the reference label at sample locations,
13
