Chanin Tinnachote , Chalermchon Satirapod Dept. of Survey Engineering, Chulalongkorn University

1. Improving the GPS signal reception capability of Leica GS20 receiver with low cost GPS antenna for the development of AM/FM/GIS project of Thai Provincial Electricity Authority ChaninTinnachote, ChalermchonSatirapod Dept. of Survey Engineering, Chulalongkorn University AgamonChantaraklom and NontachaiYoothai Network Operation Department, Provincial Electricity Authority Asia Geospatial Forum 2012, Hanoi, Vietnam.

2. Outline 1. PEA 2. AM/FM/GIS Project 3. Testing Procedure and Results 4. Discussion of Results 5. Conclusion

3. 1. Provincial Electricity Authority What is PEA ? A power utility state enterprise which responsible for supplying electricity for all regions of Thailand outside of metropolitan Bangkok.

4. 2. AM/FM/GIS Project • What is The AM/FM/GIS project ? • The AM/FM/GIS project is the project that improve PEA’s operation competence aims to support the other projects at PEA in order to deliver the best services to its customers. • The spatial data capturing and maintenance task is considered as one of the major part . It involves building and updating of large spatial database. (i.e. base map, electricity poles, cables, transformers and meters)

5. 2. AM/FM/GIS Project

6. 2. PEA AM/FM/GIS Project • Accuracy • 1 meter municipal areas • 5 meter in other area. • GPS technology has been chosen as a main tool for the positional data surveying procedure.

7. 2. PEA AM/FM/GIS Project • Data capture with LeicaGS20 GPS receivers • LeicaGS20 GPS receivers have been purchased and distributed to every provincial and district office of PEA . • But the initialization time of some receivers is relative slow and in some cases this could take up to 30 minutes. • LeicaAT501 external antenna • Reduce a signal acquisition time but rather expensive while the project budget was already spent • Trying to relieve the situation with limited resources, PEA engineer team has come up with the same ideas of using a low-cost GPS antenna to increase the GS20’s signal tracking performance.

8. 2. PEA AM/FM/GIS Project • What is “Smart Hat” and “Smart Bag ? • They are both equipped with a low-cost external antenna (Holux AR-01 model) and re-radiation kit (Holux AR-10 model). • Although they are quite similar, the “Smart Bag” device has been configured to be more enduring and stable. It was then chosen to be further studied for its capability and performance AR-10 AR-01 GS 20

9. 2. PEA AM/FM/GIS Project 2 Smart Hat 1. GPS Leica GS-20 & Hat 2. Antenna AR-01 3. Radiator AR-10 4. Battery Radiator 1 3 4

10. 2. PEA AM/FM/GIS Project 6 • Smart Bag • 1. GPS Leica GS-20 • 2. GPS Leica GS-20 Batteries • 3. GPS Leica GS-20 Adapter • 4. Radiator battery • 5. Radiator AR-10 • 6. Antenna AR-01 • 7. Tripod 5 4 1 3 7 2 Figure 1 The Smart Bag system developed by PEA (PEA, 2011)

11. 3. Testing Procedure and Results • Testing • Signal acquisition time test • first attempt almanac file • second attempt delete almanac fille • Data quality test • Carrier phase test • Pseudorange test

12. With external antenna With Smart Bag 3. Testing Procedure and Results • Signal acquisition time test • aims to check whether the use of the Smart Bag can yield the similar signal acquisition time as the use of external geodetic-graded GPS antenna. • By use of two LeicaGS20 receivers, the first receiver connected with the Smart Bag while the second receiver connected with the external geodetic-graded GPS antenna.

13. With external antenna With Smart Bag 3.Testing Procedure and Results • first attempt • switched both receivers on at the same time • recorded the period used until each receiver yields the first 3D coordinate solution, so-called ‘initialization time’. This test was repeated for 10 times. • second attempt • reset the receiver’s memory to clear up the almanac file And turning off . • switched both receivers on at the same time • recorded the initialization time. This test was repeated for 10 times Figure 2 Signal acquisition time test architecture

14. Testing Procedure and Results • Table 1 Comparison of Initialization time with an almanac file • Table 2 Comparison of Initialization time deleting an almanac file

15. 3. Testing Procedure and Results • Data quality test • Carrier phase measurement test • Pseudorange measurement test Figure 3 Data collection at CU01 site, Chulalongkorn University, Bangkok, Thailand

16. 3.Testing Procedure and Results • Carrier phase measurement test • Aims to check whether the Smart Bag system can produce reliable carrier phase measurements. • Set up the low-cost antenna on the CU01 point . The coordinates of CU01 site are known and accurate at millimeter level (Satirapod, 2005) • Collected in static mode for approximately 5 hours at a 15-second sampling rate. • The IGS CUSV station which is located nearby the CU01 site, was downloaded and processed together with the data from CU01 site using the Leica Geomatic Office (LGO) software. • The result • The differences in the north and east components are at 1.31 cm and 1.33 cm, respectively

17. 3.Testing Procedure and Results • Pseudorange measurement test • Aims to check whether the pseudorange measurements obtained from the Smart Bag system can produce reliable coordinate solutions. • Set up the low-cost antenna on the CU01. • Collected the data at CU01 point for approximately 3 hours using the stream mode. The stream mode will automatically store instantaneous coordinate solution in a log file at 15-second rate. • The IGS CUSV station was downloaded and processed together with the data from CU01 site using the LeicaGeomatic Office (LGO) software.

18. 3. Testing Procedure and Results • The result of Pseudorange measurement test • Table 3 A summary of statistics obtained from the Smart Bag system • The unexpected large discrepancies are observed. There might be a signal intervention from outside because the re-radiation kit was half opened and this could lead to unexpected errors in GPS pseudorange observations • We decided to run the similar test for approximately 5 hours with two SMART bag systems, one set up in a close box and another one set up in an open box

19. 3. Testing Procedure and Results • The result of Pseudorange measurement test • Table 4 A summary of statistics obtained from the Smart Bag system

20. 4. Discussion of Results • The signal tracking performance of the Smart Bag • The use of both Smart bag and external antenna can significantly improve the signal acquisition time as compared to the use of internal antenna. • Referring to Tables 1 and 2, the averaged initialization times between the use of Smart Bag and the external antenna are not statistically different. • Thus, it can be concluded that the signal tracking performance of the Smart Bag is the same level as the external geodetic-graded GPS antenna.

21. 4. Discussion of Results • The quality of carrier phase and pseudorange observations of the Smart Bag • For the carrier phase measurement testas presented , it is clearly seen that the obtainable accuracy is at centimeter accuracy. • This therefore confirms that the quality of carrier phase measurements obtained from the Smart Bag is high and the Smart Bag can be used for high accuracy applications. • In case of pseudorange measurements test, large errors were found when the box was half opened during the field data collection. It might be caused by an intervention of bouncing signal into the receiver. • This is confirmed by the second test which compares a performance of the Smart Bag in an open box and a close box. • The quality of pseudorange measurements is considered as the same quality as the use of external antenna.

22. 5. Conclusion • This paper presents the test results of the developed Smart Bag. • Results obtained from the signal acquisition time test confirmed that both the Smart Bag and the external geodetic-graded antenna yield similar performance. • In addition, the use of Smart Bag still maintains positional accuracy at cm level and meter level with the use of carrier phase and pseudorange observations, respectively. • recommended that when using the Smart Bag system for data collection, the box have to be closed in order to prevent any possible signal intervention. • Therefore, the Smart Bag can be used to replace the use of external antenna without deteriorating an initialization time and an obtainable accuracy.

23. Any Questions ?

24. Thank you for your attention

25. Advantage of Smart Bag • Low Price • duration time of GPS Battery longer • Reduce damage of connector