RELIABILITY ANALYSIS OF GPS DATA

Abstract

A reliability of GPS data has not been reported which is taken by various GPS receivers at a same time in Geornatics Engineering field. Previous results have dealt only with the test-retest reliability coefficients of one or more items or data. The purpose of this study is to provide a comprehensive reliability analysis of the GPS data. More specifically the problem of this study were I) to determine the test - retest reliability coefficients of the GPS data 2) to determine the standard error of measurement of the data as computed by the standard correlation formula method during various time intervals of the day and with different logging rates and 3) to compare which GPS receiver is more reliable between - them. Four types of GPS receivers were used for taking the data. Those were Dual Code (Juno SB) and Single Frequency GPS receivers (ProMark 120, R-3 and GRX-2) .The planimetric parameters were used for the analysis purpose which includes the latitude, longitude and elevation. The data obtained from each GPS receiver were analyzed in order to obtain the reliability coefficient of the data and standard error of measurement computed by the standard correlation formula method. Considering all (i.e. time interval and logging interval) the highest reliability achieved for latitude by Ashtech ProMark 120 (0.98287792) from 3pm-4pm for 10 second logging interval, for longitude by Trimble R-3 (0.972459028) from 1pm-2pm for I second interval and for ellipsoidal height by Sokkia GRX-2 (0.974075585) from3pm-4pm for I second interval. The lowest Standard Error of Measurement (i.e. SEM) is found for latitude by Ashtech ProMark 120 (4.95 E-07) from 11am- 12pm for 1 second interval, for longitude by Ashtech ProMark 120 (8.44E-07) from I lam-I2pm for I second interval and for ellipsoidal height by Ashtech ProMark 120 (0.180371828) from llam-12pm for 1 second interval