Thematic Accuracy Assessment Procedures

116 Pages·2010·2 MB·English

National Park Service
U.S. Department of the Interior

Natural Resource Program Center

Thematic Accuracy Assessment Procedures
National Park Service Vegetation Inventory, Version 2.0
Natural Resource Report NPS/NRPC/NRR—2010/204
ON THE COVER
National Park Service staff record field data for a thematic accuracy assessment of a vegetation map at Joshua Tree National Park.
National Park Service photograph by Chris Lea.
Thematic Accuracy Assessment Procedures
National Park Service Vegetation Inventory, Version 2.0
Natural Resource Report NPS/NRPC/NRR—2010/204

Chris Lea
National Park Service
Vegetation Inventory
P.O. Box 25287 (Academy Place)
Denver, CO 80225

Anthony C. Curtis
National Park Service
Southeast Coast Inventory and Monitoring Network
P.O. Box 806
Saint Marys, GA 31558
June 2010
U.S. Department of the Interior
National Park Service
Natural Resource Program Center
Fort Collins, Colorado
The National Park Service, Natural Resource Program Center publishes a range of reports that
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Park Service and others in natural resource management, including scientists, conservation and
environmental constituencies, and the public.
Natural Resource Reports are the designated medium for disseminating high priority, current
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audience, and may contain NPS policy considerations or address sensitive issues of management
applicability.
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audience, and designed and published in a professional manner.
This report received formal peer review by subject-matter experts who were not directly
involved in the collection, analysis, or reporting of the data, and whose background and expertise
put them on par technically and scientifically with the authors of the information.

Views, statements, findings, conclusions, recommendations, and data in this report are those of
the author(s) and do not necessarily reflect views and policies of the National Park Service, U.S.
Department of the Interior. Mention of trade names or commercial products does not constitute
endorsement or recommendation for use by the National Park Service.

This report is available from the National Park Service Vegetation Inventory website
(http://science.nature.nps.gov/im/inventory/veg/index.cfm) and from the Natural Resource
Publications Management website (http://www.nature.nps.gov/publications/NRPM).
Please cite this publication as:
Lea, C. and A. C. Curtis. 2010. Thematic accuracy assessment procedures: National Park Service
Vegetation Inventory, version 2.0. Natural Resource Report NPS/2010/NRR—2010/204.
National Park Service, Fort Collins, Colorado.
NPS 999/102741, June 2010
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Contents

Page

Contents ......................................................................................................................................... iii

Figures........................................................................................................................................... vii

Tables ............................................................................................................................................. ix

Appendices and Exhibits................................................................................................................ xi

Executive Summary ..................................................................................................................... xiii

Acknowledgments......................................................................................................................... xv

1.0 Introduction ............................................................................................................................... 1

1.1 Thematic Accuracy Assessment, NPS Vegetation Inventory, 1994-2009 ........................ 1

1.2 Summary of Changes from 1994 Guidance....................................................................... 5

1.3 Key Requirements and Best Practices ............................................................................... 6

1.4 Work Flow ......................................................................................................................... 9

2.0 Sampling Design ..................................................................................................................... 15

2.1 Sampling Design and Data Collection Objectives ........................................................... 15

2.2 Observation Area (Minimum Mapping Unit) Size .......................................................... 15

2.3 Inference Area Selection .................................................................................................. 18

2.3.1 Included and Excluded Map Classes ....................................................................... 18

2.3.2 Areas with Training Sites ......................................................................................... 19

2.3.3 Adjustments for Access Costs................................................................................... 19

2.3.4 Adjustments to Achieve Sample Data Homogeneity in Observations ...................... 21

2.3.5 Adjustments for Independence Among Observations .............................................. 22

2.4 Sampling Methods ........................................................................................................... 24

2.5 Determining Sample Sizes ............................................................................................... 25

2.5.1 Determining Acceptable Levels of Error and Confidence ....................................... 25

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2.5.2 Number of Observations per Map Class .................................................................. 26

2.6 Geographic Information Systems Design Considerations ............................................... 28

3.0 Field Methods (Response Design) .......................................................................................... 29

3.1 Considerations that Affect the Selection of a Source of Higher Accuracy ..................... 29

3.2 Field Methodology........................................................................................................... 33

3.2.1 Field Observer Skill Level Considerations .............................................................. 33

3.2.2 Safety and Efficiency ................................................................................................ 35

3.2.3 Basic Navigation ...................................................................................................... 36

3.2.4 Field Navigation Supplements and Retaining Independence from Mapping .......... 37

3.2.5 Determination of Vegetation Type in the Field........................................................ 37

3.2.6 Moving or Reshaping Observation Area ................................................................. 38

3.2.7 Recording Field Position (GPS methods) ................................................................ 40

3.2.8 Reporting Field Data ............................................................................................... 41

3.2.9 Missed Sites .............................................................................................................. 41

4.0 Data Analysis .......................................................................................................................... 43

4.1 Accuracy Assessment Data.............................................................................................. 44

4.2 The Sample Contingency Table ....................................................................................... 44

4.3 The Population Contingency Table ................................................................................. 46

4.4 Definitions of Measures of Overall Accuracy ................................................................. 47

4.5 Users’ and Producers’ Accuracies Measures for Individual Map Classes ...................... 47

4.6 Computations of Accuracy Measures under Stratified Random Sampling ..................... 48

4.6.1 Computation of Measures of Users’ Accuracies .................................................... 48

4.6.2 Computation of Measures of Producers’ Accuracies ............................................. 49

4.6.3 Computation of Measures of Overall Accuracy...................................................... 51

4.7 Lumped Classes ............................................................................................................... 52

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4.8 Design and Formatting for Contingency Tables ..................................................................... 53

5.0 Reporting Requirements ......................................................................................................... 57

Literature Cited ............................................................................................................................. 59

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Figures

Page

Figure 1. Work Flow of operational phases of an NPS Vegetation Inventory Project. .............. 13

Figure 2. Relationship between Sample Size (N), Confidence Interval Width, and

Confidence Level for two different values of the point estimate of accuracy ( pˆ ). ..................... 26

Figures 3A-D. Examples of Providing Field Maps Suitable as Navigation Aids for Thematic

Accuracy Assessment, Thomas Stone National Historical Site (Maryland). ............................... 72

Figures 4A-D. Examples of Providing Field Maps Suitable as Navigation Aids for Thematic

Accuracy Assessment, Joshua Tree National Park (California), USGS Conejo Wells 7.5

minute quadrangle. ........................................................................................................................ 73

Figures 5A-B. Examples of Providing Field Maps Suitable as Navigation Aids for Thematic

Accuracy Assessment, Joshua Tree National Park (California), USGS Yucca Valley 7.5

minute quadrangle. ........................................................................................................................ 74

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