Assessing the Accuracy of OpenStreetMap Data in South Africa for the purpose of integrating it with

144 Pages·2014·4.22 MB·English

Assessing the Accuracy of OpenStreetMap Data in South Africa for the
Purpose of Integrating it with Authoritative Data
By Lindy-Anne Siebritz under the supervision of Dr George Sithole
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A dissertiation presented for the degree
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Master of Science in Engineering
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Department of Architecture, Planning and Geomatics
University of Cape Town
February 2014
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The copyright of this thesis vests in the author. No
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quotation from it or information derived from it is to be

published without full acknowledgeement of the source.
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The thesis is to be used for private study or non-
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commercial research purposes only.

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Published by the Universit y of Cape Town (UCT) in terms
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of the non-exclusive license granted to UCT by the author.
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PLAGIARISM DECLARATION
1. I know that plagiarism is wrong. Plagiarism is to use another’s work and pretend
that it is one’s own.
2. IhaveusedtheHarvardconventionforcitationandreferencing. Eachcontribution
to, andquotationinthisthesisfromtheworksofotherpeoplehasbeenattributed,
and has been cited and referenced.
3. This thesis is my own work.
4. I have not allowed, and will not allow, anyone to copy my work with the intention
of passing it off as his or her own work.
Signature
Date
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ACKNOWLEDGEMENTS
This dissertation is unto the glory of the Lord. All of the honour belongs to Him.
Iamgratefultomysupervisor, DrGeorgeSitholeforhispatienceandguidance. Iwould
like to thank my parents and good friend, Simonne for their prayers and encouragement.
Ahmad Desai and Thabo Ntsoku provided me with technical assistance. The Open-
StreetMapdatabaseadministratorsGrantSlaterandFrederickRammprovidedmedata
and answered all my questions. I would like to extend my thanks to all of them.
Finally, I would like to thank my colleagues who provided me with information, Aslam
Parker, Mark McLachlan, Steve Jansen, Raoul Duesimi, Sissiel Kay and Heinrich Du
Plessis.
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Contents
1 INTRODUCTION 12
1.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
1.2 Background . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
1.2.1 The Chief Directorate: National Geo-Spatial Information Inte-
grated Topographical Information System . . . . . . . . . . . . . . 14
1.2.2 OpenStreetMap . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
1.2.3 OpenStreetMap Data Model . . . . . . . . . . . . . . . . . . . . . 16
1.3 Related Work . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
1.3.1 Status of the South African Spatial Data Infrastructure . . . . . . 16
1.3.2 VGI in the SDI Context . . . . . . . . . . . . . . . . . . . . . . . . 17
1.3.3 Quality, Quality Assurance and Quality Control . . . . . . . . . . 18
1.3.4 Quality Assessment . . . . . . . . . . . . . . . . . . . . . . . . . . 18
1.4 Problem Identification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
1.5 Research Objectives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
1.5.1 Research Questions . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
1.6 Methodology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
1.6.1 Quantitative Assessments . . . . . . . . . . . . . . . . . . . . . . . 20
1.6.2 Qualitative Assessments . . . . . . . . . . . . . . . . . . . . . . . . 20
1.7 Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
1.8 Outcomes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
2 LITERATURE REVIEW 24
2.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
2.2 Volunteered Geographic Information . . . . . . . . . . . . . . . . . . . . . 24
2.2.1 Advantages of VGI . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
2.2.2 Disadvantages of VGI . . . . . . . . . . . . . . . . . . . . . . . . . 27
2.2.3 Examples of VGI Initiatives Available in South Africa . . . . . . . 28
2.2.4 Factors Leading to the Success of VGI . . . . . . . . . . . . . . . . 30
2.2.5 Factors Opposing VGI Success . . . . . . . . . . . . . . . . . . . . 31
2.3 Spatial Data Infrastructure and VGI . . . . . . . . . . . . . . . . . . . . . 33
2.3.1 The Purpose of SDI . . . . . . . . . . . . . . . . . . . . . . . . . . 33
2.3.2 Integrating VGI and Authoritative Data . . . . . . . . . . . . . . . 33
2.3.3 Global Examples of VGI and SDI/NMA Integration . . . . . . . . 34
2.4 Methods to Assess Quality . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
2.4.1 Positional Accuracy of Linear Features . . . . . . . . . . . . . . . . 35
2.4.2 Geometric Accuracy of Polygon Features . . . . . . . . . . . . . . 39
2.4.3 PreviousInvestigationsintothePositionalAccuracyofOSMRoads
Using the Goodchild and Hunter (1997) Method . . . . . . . . . . 40
2.4.4 Semantic Accuracy . . . . . . . . . . . . . . . . . . . . . . . . . . . 41
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2.4.5 Completeness Assessments. . . . . . . . . . . . . . . . . . . . . . . 41
2.5 Analysis and Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
3 CHIEF DIRECTORATE: NATIONAL GEO-SPATIAL INFORMA-
TION AND OPENSTREETMAP SPATIAL DATA MODELS 45
3.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
3.2 Spatial Data Standards . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
3.2.1 Spatial Data Standards in South Africa . . . . . . . . . . . . . . . 45
3.2.2 Duties of the Committee for Spatial Information . . . . . . . . . . 46
3.2.3 CD: NGI Spatial Data Standards - Contributions from External
Standards . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47
3.2.4 The CD: NGI Internal Spatial Data Standards . . . . . . . . . . . 47
3.3 CD: NGI Topographical Data Structure . . . . . . . . . . . . . . . . . . . 47
3.3.1 Topographic Feature Compilation . . . . . . . . . . . . . . . . . . 47
3.3.2 Standards Governing Topographic Feature Compilation . . . . . . 48
3.3.3 CD: NGI Quality Control . . . . . . . . . . . . . . . . . . . . . . . 49
3.3.4 CD: NGI Quality Topology . . . . . . . . . . . . . . . . . . . . . . 49
3.3.5 Distribution of the CD: NGI Data . . . . . . . . . . . . . . . . . . 49
3.4 OpenStreetMap Data Structure . . . . . . . . . . . . . . . . . . . . . . . . 51
3.4.1 OpenStreetMap Data Elements . . . . . . . . . . . . . . . . . . . . 51
3.4.2 OpenStreetMap Data Model Components . . . . . . . . . . . . . . 52
3.4.3 OpenStreetMap Quality Control . . . . . . . . . . . . . . . . . . . 53
3.4.4 OpenStreetMap Topology . . . . . . . . . . . . . . . . . . . . . . . 54
3.4.5 Distribution of Data . . . . . . . . . . . . . . . . . . . . . . . . . . 57
3.5 Analysis and Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57
4 METHODOLOGY 60
4.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60
4.2 Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61
4.2.1 Data Sources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61
4.2.2 Co-ordinate System and Projection . . . . . . . . . . . . . . . . . . 61
4.2.3 Selection of Test Areas . . . . . . . . . . . . . . . . . . . . . . . . . 61
4.3 Data Cleaning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64
4.3.1 Filtering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64
4.4 Method for Quantitative Assessment . . . . . . . . . . . . . . . . . . . . . 66
4.4.1 Positional Accuracy of Roads . . . . . . . . . . . . . . . . . . . . . 66
4.4.2 Geometric Accuracy Of Polygon Buildings . . . . . . . . . . . . . . 70
4.4.3 Semantic Accuracy of Roads . . . . . . . . . . . . . . . . . . . . . 73
4.4.4 Completeness of Roads . . . . . . . . . . . . . . . . . . . . . . . . 76
4.5 Method for Qualitative Assessment . . . . . . . . . . . . . . . . . . . . . . 76
4.5.1 OSM Currency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76
4.5.2 OSM Uniformity in Acquisition . . . . . . . . . . . . . . . . . . . . 79
4.6 Analysis and Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79
5 RESULTS AND ANALYSIS 83
5.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83
5.2 Results for Quantitative Assessments . . . . . . . . . . . . . . . . . . . . . 83
5.2.1 Positional Accuracy of Roads . . . . . . . . . . . . . . . . . . . . . 83
5.2.2 Geometric Accuracy of Amenity Buildings . . . . . . . . . . . . . . 88
5.2.3 Semantic Accuracy of Roads . . . . . . . . . . . . . . . . . . . . . 94
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5.2.4 Completeness . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 96
5.3 Results for Quantitative Assessments . . . . . . . . . . . . . . . . . . . . . 98
5.3.1 OSM Currency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98
5.3.2 OSM Uniformity of Point Acquisition . . . . . . . . . . . . . . . . 101
5.3.3 Analysis and Discussion . . . . . . . . . . . . . . . . . . . . . . . . 103
6 INTEGRATION 106
6.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 106
6.2 Previous Investigations into Integrating Authoritative Data and OSM Data106
6.3 Technical Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . 107
6.3.1 Different Reference Systems . . . . . . . . . . . . . . . . . . . . . . 107
6.3.2 Different Representations of Topographical Features . . . . . . . . 108
6.3.3 Duplication of Features . . . . . . . . . . . . . . . . . . . . . . . . 109
6.3.4 Omission of Attribute and Metadata . . . . . . . . . . . . . . . . . 109
6.3.5 Different File Formats . . . . . . . . . . . . . . . . . . . . . . . . . 112
6.3.6 The Physical and Structural Differences of the Databases . . . . . 112
6.4 Policies, Licensing and Spatial Data Standards . . . . . . . . . . . . . . . 112
6.4.1 The CD: NGI Policy and OSM Licensing Concerning Data Distri-
bution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 112
6.4.2 Adherence to the CD: NGI Spatial Data Standards . . . . . . . . . 113
6.5 Differences in Quality Assurance and Quality Control Processes . . . . . . 113
6.6 The Process for Acquiring and Processing Ancillary Data . . . . . . . . . 114
6.6.1 Using OSM Data for Change Detection . . . . . . . . . . . . . . . 115
6.6.2 Proposed Integration of the CD: NGI and OSM Data . . . . . . . 115
6.6.3 Institutional Reorganisation Needs . . . . . . . . . . . . . . . . . . 117
6.7 Analysis and Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . 117
7 CONCLUSIONS AND RECOMMENDATIONS 119
7.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 119
7.2 OSM Positional Accuracy . . . . . . . . . . . . . . . . . . . . . . . . . . . 119
7.3 Qualitative Aspects of the OSM Data . . . . . . . . . . . . . . . . . . . . 120
7.3.1 Heterogeneity in OSM Data Volumes . . . . . . . . . . . . . . . . . 120
7.3.2 Heterogeneity in OSM Data Acquisition . . . . . . . . . . . . . . . 121
7.4 Integration Opportunities . . . . . . . . . . . . . . . . . . . . . . . . . . . 122
7.5 Analysis and Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . 122
7.6 Recommendations and Future Work . . . . . . . . . . . . . . . . . . . . . 123
APPENDICES 124
A1. Appendix A: Secondary Activity Level . . . . . . . . . . . . . . . . . . . . 125
B1. Appendix B: CD: NGI Process for Compilation of Topographical Features 126
C1. Appendix C: Data flow for after approved compilation task . . . . . . . . . 127
D1. Appendix D: OSM Data Model Components . . . . . . . . . . . . . . . . . 128
E1. Appendix E: Data flow for acquisition and macro processing of ancillary
data: ad hoc . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 129
F1. Appendix F: Sample Python scripts . . . . . . . . . . . . . . . . . . . . . . 130
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List of Figures
1.1 Extract from Wikimapia . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
1.2 Extract from OpenStreetMap . . . . . . . . . . . . . . . . . . . . . . . . . 14
1.3 Integration of the CD: NGI data through the iTIS . . . . . . . . . . . . . 15
1.4 Map showing twenty-seven test areas . . . . . . . . . . . . . . . . . . . . . 19
1.5 Flowchart outlining the methodology . . . . . . . . . . . . . . . . . . . . . 21
2.1 Example of update via MapShare . . . . . . . . . . . . . . . . . . . . . . . 29
2.2 Example of the on-line Waze application . . . . . . . . . . . . . . . . . . . 30
2.3 Depiction of the BOS and Goodchild and Hunter method . . . . . . . . . 37
2.4 Depiction of the Hausdorff and average distance . . . . . . . . . . . . . . . 38
2.5 Example of the minimum bounding rectangle around a polygon . . . . . . 40
3.1 Extract of CD: NGI feature classification . . . . . . . . . . . . . . . . . . 50
3.2 OSM feature classification . . . . . . . . . . . . . . . . . . . . . . . . . . . 54
3.3 Example of OSM lines overlap errors . . . . . . . . . . . . . . . . . . . . . 55
3.4 Example of OSM polygons overlap errors . . . . . . . . . . . . . . . . . . 56
3.5 Example of OSM dangles . . . . . . . . . . . . . . . . . . . . . . . . . . . 57
4.1 Example of Residential land use - high urban density area . . . . . . . . . 62
4.2 Example of Residential land use - low urban density area . . . . . . . . . 63
4.3 Example of commercial and industrial storage area . . . . . . . . . . . . . 63
4.4 Example of features with multiple negative OSM IDs . . . . . . . . . . . . 65
4.5 Removing holes from OSM polygons . . . . . . . . . . . . . . . . . . . . . 66
4.6 Method for removing unwanted OSM road sections . . . . . . . . . . . . . 68
4.7 Example of discontinuities in OSM multi-lane road . . . . . . . . . . . . . 69
4.8 Identifying the corresponding roads between the CD: NGI and OSM . . . 70
4.9 Identifying corresponding polygons between the CD: NGI and OSM . . . 71
4.10 Example of multiple polygon matches . . . . . . . . . . . . . . . . . . . . 71
4.11 Example of incorrect polygon matching . . . . . . . . . . . . . . . . . . . 73
4.12 Point deletions, additions, modifications and no change. . . . . . . . . . . 77
4.13 Line deletions, additions, modifications and no change . . . . . . . . . . . 78
4.14 Identifying corresponding polygons between consecutive data sets . . . . . 79
4.15 Example of the line matching technique failing . . . . . . . . . . . . . . . 80
4.16 CD: NGI and OSM point data for Western Cape Commercial test area . . 81
4.17 Comparing CD: NGI and OSM point data . . . . . . . . . . . . . . . . . . 82
5.1 Percentage overlap for OSM roads . . . . . . . . . . . . . . . . . . . . . . 84
5.2 Depiction of the Mpumalanga data set with north-westerly shift . . . . . 85
5.3 Scatter plots comparing the CD: NGI and OSM road lengths . . . . . . . 87
5.4 Example of generalisation applied to polygons at the CD: NGI . . . . . . 89
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5.5 Comparing the CD: NGI and OSM compactness values for commercial
test areas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92
5.6 ComparingtheCD:NGIandOSMcompactnessvaluesforresidentialtest
areas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92
5.7 Comparing compactness for the Free State residential data set . . . . . . 93
5.8 Distribution of the compactness differences for the Free State residential
test area . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93
5.9 Graph comparing the standard errors for the CD: NGI and OSM road
class matches . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 96
5.10 Comparing completeness of OSM line data for commercial areas . . . . . 97
5.11 Comparing completeness of OSM line data for residential areas . . . . . . 97
5.12 Comparing completeness of OSM line data for low urban density areas . . 98
5.13 Comparing OSM additions 2006-2012 . . . . . . . . . . . . . . . . . . . . 99
5.14 Comparing OSM unchanged data 2006-1012 for commercial areas . . . . . 100
5.15 Comparing OSM unchanged data 2006-1012 for residential areas . . . . . 100
5.16 Comparing OSM unchanged data 2006-1012 for low urban density areas . 101
5.17 Distribution of point contributions for commercial areas . . . . . . . . . . 102
5.18 Distribution of point contributions for residential areas . . . . . . . . . . . 102
5.19 Distribution of point contributions for low urban density areas . . . . . . 103
6.1 Example of different feature types representing the same feature . . . . . 109
6.2 Example of JOSM file format containing the source information . . . . . . 111
6.3 Process for ingesting OSM data into the CD: NGI iTIS . . . . . . . . . . 116
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List of Tables
3.1 Description of OSM data elements . . . . . . . . . . . . . . . . . . . . . . 52
3.2 Comparison of CD: NGI and OSM data models . . . . . . . . . . . . . . . 59
4.1 Quality measures undertaken for each OSM data element . . . . . . . . . 61
4.2 Sample matrix comparing the number of road matches . . . . . . . . . . . 74
4.3 Comparing some of the CD: NGI and OSM road classes . . . . . . . . . . 75
4.4 Positive road class matches between the CD: NGI and OSM . . . . . . . . 76
5.1 Percentage overlap for OSM roads per province . . . . . . . . . . . . . . . 86
5.2 Percentage overlap for OSM roads per settlement category . . . . . . . . . 86
5.3 Comparing the Hausdorff distances for polygons . . . . . . . . . . . . . . 88
5.4 Comparing the area ratios of matching polygons . . . . . . . . . . . . . . 90
5.5 Comparing compactness differences for commercial test areas . . . . . . . 91
5.6 Comparing compactness differences for residential test areas . . . . . . . . 91
5.7 Comparing the elongation differences for commercial test areas . . . . . . 94
5.8 Comparing the elongation differences for residential test areas . . . . . . . 94
5.9 Percentages for the CD: NGI and OSM road class matches. . . . . . . . . 95
7.1 Table of OSM compatibility . . . . . . . . . . . . . . . . . . . . . . . . . . 123
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