UNIT 45 - ACCURACY OF SPATIAL DATABASES

UNIT 45 - ACCURACY OF SPATIAL DATABASES

Compiled with assistance from Nicholas R. Chrisman, University

UNIT 45 - ACCURACY OF SPATIAL DATABASES

Compiled with assistance from Nicholas R. Chrisman, University

A. INTRODUCTION

B. DEFINITIONS

Accuracy

Precision

Components of data quality

B. POSITIONAL ACCURACY

How to test positional accuracy?

C. ATTRIBUTE ACCURACY

How to test attribute accuracy?

How to summarize the matrix?

E. LOGICAL CONSISTENCY

F. COMPLETENESS

G. LINEAGE

H. ERROR IN DATABASE CREATION

Positional measurement error

Attribute errors

Compilation errors

Processing errors

I. DATA QUALITY REPORTS

USGS

British Ordnance Survey

US National standards

REFERENCES

Bureau of the Budget, 1947. National Map Accuracy Standards, Washington DC, GPO, reprinted in M.M.Thompson, 1979, Maps for America, USGS, Reston VA, p 104.

Burrough, P.A., 1986. Principles of Geographical Information Systems for Land Resources Assessment, Clarendon Press, Oxford. See pp. 103-135.

DCDSTF, 1988. "The Proposed Standard for Digital Cartographic Data," The American Cartographer 15(1):entire issue.

Federal Geodetic Control Committee, 1974. Classification, Standards of Accuracy, and General Specifications of Geodetic Control Surveys, Washington DC, GPO, 1980-0- 333-276 (also NOAA--S/T 81-29).

Harley, J. B., 1975. Ordnance Survey Maps: A Descriptive Manual, Ordnance Survey, Southampton, England.

Merchant, D.C., 1987. "Spatial accuracy specification for large scale topographic maps," Photogrammetric Engineering and Remote Sensing 53:958-61. Reports a recent effort by ASPRS to revise the US National Map Accuracy Standard.

National Committee for Digital Cartographic Data Standards, Moellering, H., ed, 1985. Digital Cartographic Data Standards: An Interim Proposed Standard, Report #6.

DISCUSSION AND EXAM QUESTIONS

1. Explain the difference between accuracy and precision, and show how these ideas apply to GIS.

2. "In manual map analysis, precision and accuracy are similar, but in GIS processing, precision frequently exceeds the accuracy of the data". Discuss

3. Design an experiment to measure the accuracy achieved by an agency in its digitizing operations. How would you measure the accuracy with which lines are being digitized?

4. What is meant by data lineage, and why is it important in understanding the accuracy of spatial databases?


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