Geography ETDs

Publication Date

8-27-2009

Abstract

Global Positioning Systems devices are increasingly being used for data collection in many fields. Consumer-grade GPS units without differential correction have a published horizontal accuracy of approximately 10 to 15 meters (average error). An attractive option for differential correction for these GPS units is the Wide Area Augmentation System (WAAS). Most consumer-grade GPS units on the market are WAAS capable. According to the FAA, the WAAS broadcast message provides integrity information about the GPS signal as well as accuracy improvements which are reported to improve accuracy to 3 to 5 meters. However, limited empirical evidence has been published on the accuracy of WAAS-enabled GPS compared to autonomous GPS. Results are presented of an empirical study comparing the horizontal and vertical accuracy of WAAS corrected GPS and autonomous GPS under ideal conditions using consumer-grade receivers. Data were collected for thirty minute time spans over accurately surveyed control points. Metrics of median, 68th and 95th percentile, RMSE and average positional error in x, y and z were computed and statistically tested with a hypothesis test. There was no statistical difference found between WAAS and autonomous position fixes when using two different consumer-grade units. A statistical difference was evident in a third unit type tested. Analysis of data collected for a twenty seven hour time span indicates that while WAAS is altering the estimated position of a point compared to autonomous position estimate, WAAS augmentation actually appears to increase the positional error.

Degree Name

Geography

Department Name

Geography

Level of Degree

Masters

First Committee Member (Chair)

Matthews, Paul

Second Committee Member

Benedict, Karl

Third Committee Member

Stone, William

Document Type

Thesis

Project Sponsors

New Mexico Geographic Information Council

Language

English

Keywords

GPS receivers--Testing, Mobile geographic information systems--Evaluation, Global Positioning System.

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