THE UNIVERSITY OF NEW SOUTH WALES

GMAT 4001:  THESIS PART B

SEMESTER 2, 2008

 

Author:          Thomas Barker z3130283

Supervisor:    Chris Rizos

  

DEVELOPING TEST STRATEGIES FOR GPS RECEIVERS: FROM CONSUMER DEVICES TO TOP-OF-THE-LINE SURVEY-GRADE RECEIVERS

 

Introduction       Test Procedure       Results      Analysis       Contacts        References     

 

Introduction

Global Navigation Satellite Systems (GNSS) are making an increasing and extremely productive contribution to society’s day-to-day activities as well as revolutionising the surveying and spatial information industry.  Advances in the technology and the development of new techniques and methods have seen the achievable accuracies of GNSS receivers – particularly the United State’s Global Positioning System (GPS) – improve dramatically since the inception of GPS’s full operational capability (FoC) in 1995(NavCen 1995[a]).  Yet despite the ever-increasing popularity of these convenient positioning devices, there are few readily accessible procedures available for users to test their equipment and gain a better understanding of the comparative performance of different receivers. 

From this project, a procedure has been developed by which different types of GPS receivers can be tested and compared under controllable conditions.  As such, an assessment and analysis of the performance of some commonly used consumer-type and survey-grade GPS receivers running in Single Point Positioning (SPP) mode has been developed based on GPS’s Standard Positioning Service (SPS). 

 

 Table 1:  List of receivers used for testing

Receiver

Use

Channels*

Stated Accuracy*

Update Rate*

Number of digits**

Garmin Etrex

Handheld/recreational

12

≤15 metres RMS

1/sec

4

Garmin GPSmap76

Handheld/recreational/land and marine based use

12

≤15 metres RMS

1/sec

4

Leica 1200 series

Survey

12

 

1 or 2/sec

7

Raymarine Raystar 125

Marine (integrated antenna/receiver with NMEA output

12

≤15 metres RMS

 

4

San Jose GM44

Marine (integrated antenna/receiver with NMEA output

 

10 metres RMS

1/sec

5

Simrad GS10 SimNet

Marine (integrated antenna/receiver with NMEA output

12

6 metres 95%

 

3

(Garmin, 2004), (Garmin, 2001), (Leica, 2006), (Raymarine, date unknown), (San Jose, date unknown), (Simrad, 2006)

*If stated/known

**Refers to the number of digits behind the decimal place in the position recorded in the appropriate NMEA message.  The format was degrees and decimal minutes (ddmm.mm).

 

Table 1:  Positioning Accuracy Standard as defined by GPS SPS Performance Standard, 2008, p 34

Accuracy Standard

Conditions and Restraints

Global Average Positioning Domain Accuracy

§      ≤ 9 m 95% Horizontal Error

§      ≤ 15 m 95% Vertical Error

§      Defined for position/time solution meeting the representative user conditions

§      Standard based on a measurement interval of 24 hours averaged over all points within the service volume

Worst Site Positioning Domain Accuracy

§      ≤ 17 m 95% Horizontal Error

§      ≤ 37 m 95% Vertical Error

§      Defined for position solution meeting the representative user conditions

§      Standard based on a measurement interval of 24 hours for any point within the service volume