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Exercise the Capability of RTK GNSS GPS Beidou under heavy obstructions

Posted on: Jan. 12,2018

Table 1 shows explanation of condition of satellite obstruction in research area each in Jakarta, Bandung and Jambi, along with baseline definition, and time and also data set for acquisition. We choose rural dense area, rural very dense area, and forest to exercise the RTK GNSS GPS Beidou capability. Baseline from Base to Rovers all set beyond 5 kilometer and observation mostly done in the morning until afternoon.

Table 1. Research in Jakarta, Bandung, and Jambi, Included condition of obstructions, baseline definition, and time and data set for acquisition.

No. Area Name Condition and Set Up
1 Test A (*) 40% satellite obstruction in Jakarta, baseline 5 km, in the morning
2 Test B (*) 70% satellite obstruction in Bandung, Baseline 5 km, in the afternoon
3 Test C (***) 90% satellite obstruction in Jambi, baseline 1km, in the morning
4 Test land parcel 70% satellite obstruction in Bandung, baseline 5km, in the morning
(*) Rural dense area    (**) Rural very dense area    (***) Forest


III. RESULTS

We can see the average result of quality of horizontal and vertical component at research area in table 2 and 3. For area Test A, the average deviation for horizontal component is 0.05 meter for GPS only RTK observation and vertical component is 0.07 meter, while 0.02 meter for combination GPS and Beidou both for horizontal and vertical component. For area Test B the average deviation for horizontal component is 0.08 meter for GPS only and vertical component is 0.10 meter, while 0.02 meter for combination GPS and Beidou both for horizontal and vertical component. For area Test C the GPS only is 0.60 meter for horizontal and 1.01 meter for vertical, while 0.04 meter in horizontal and 0.10 in vertical when using combination of GPS and Beidou for RTK Method.

Table 2. Average result quality of horizontal component at the research area
No Area Name Average Deviation for horizontal component (in meter)
1 Test A (*) 0.05 GPS only, 0.02 GPS + Beidou
2 Test B (*) 0.08 GPS only, 0.02 GPS + Beidou
3 Test C (***) 0.60 GPS only, 0.04 GPS + Beidou
     
(*) Rural dense area    (**) Rural very dense area    (***) Forest

Table 3. Average result quality of vertical component at the research area
No Area Name Average Deviation for vertical component (in meter)
1 Test A (*) 0.07 GPS only, 0.02 GPS + Beidou
2 Test B (*) 0.08 GPS only, 0.02 GPS + Beidou
3 Test C (***) 1.01 GPS only, 0.10 GPS + Beidou
(*) Rural dense area    (**) Rural very dense area    (***) Forest

We can see graphs of plotted of horizontal component represented in figure 6 and for vertical component in figure 7. We can see distributions of GPS only testing results are sparser than GPS and Beidou combination, either for horizontal or vertical. Heavy satellite obstruction 40 percent is more accurate than 70 and 90 percent. These are the reasonable result since more obstruction more change to lose signal and cycle slip that potentially degrade the accuracy. Indeed, we can see improvement in positioning using RTK GNSS GPS Beidou.


Figure 6. Plotted of horizontal position repeatability from 100 sample of RTK GPS only measurements (red dot) and RTK GNSS GPS Beidou (black dot). First graph is for 40 percent obstruction testing result, second for 70 and the last for 90 percent.

Figure 7. Plotted of vertical position repeatability from 100 sample of RTK GPS only measurements (red dot) and RTK GNSS GPS Beidou (black dot). First graph is for 40 percent obstruction testing result, second for 70 and the last 90 percent.


Result of testing on land parcel measurement by using RTK GNSS GPS Beidou is promising. We can see on figure 8, the overlay of land parcel measurement with base map satellite image within good agreement. As for the information, in 2007 the numbers of land parcel in Indonesia that already attached by certificate were about 9 million. While in 2016 around 43 million land parcel has certificate. The total number of parcels that should equipped by certificate is more than a hundred million parcels. Progress of certification per year since 2007 is only 2-3 million. In this case, more than half of total parcel are still waiting to equipped with certificate for years to come. The expectation from Government that each year 5 million parcels should have certificate (Andreas et.al, 2017). This means we need acceleration in measurement to produce certificate on the land parcel, and maybe by using the RTK GNSS GPS Beidou it can help.

Figure 8. Simulation of land parcel measurement using RTK GNSS GPS Beidou in rural dense area in our research area in Bandung.


As for the calculation time to fixing the ambiguity, we can see the result from exercise in table 4. For the Test Area A, GPS still can fix the ambiguity but it as slower than using GPS and Beidou combination. For test area B, GPS still can fix the ambiguity but event it was very much slower than using GPS and Beidou combination. There are also float solution. For test C, using GPS only mostly unresolved for the ambiguity, but when using combination of GPS and Beidou, they are still resolved for 120-300seconds of calculation. Once again, we can see improvement in positioning using RTK GNSS GPS Beidou.


Table 4. Notes of time for ambiguity fixing in the research areas
No Area Name Time to Fixing Ambiguity (in second)
1 Test A (*) 5-20 GPS only, 5-10 GPS + Beidou
2 Test B (*) 120-300 GPS only, 5-60 GPS + Beidou
3 Test C (***) Mostly unresolved GPS only, 120-300 GPS + Beidou
(*) Rural dense area    (**) Rural very dense area    (***) Forest


III. DISCUSSION & CONCLUSION

We highlight degradation in accuracy du to obstruction disturbing the signal from the GNSS satellite to the observer. As further consequences, the need of accuracy as we expected is sometimes beyond the achievement. As for the RTK, in many cases, it would give autonomous result, float solution, hardy waiting for resolved ambiguity, and or in some case given the possibility of fixing to the wrong integer. Obviously, the obstruction will disturb the signal connection and produce cycle slip, and un-favor fixing the ambiguity. Since many applications needs to correspond to this degradation and problems (e.g. measurement like in rural dense area for land parcel measurement, in forest for boundary measurement, etc.), in this case we need to find the answer.

We might have found the answer of limitation of GNSS positioning for heavy satellite obstruction when using RTK GNSS GPS Beidou. Result of testing shows event in 40, 70 and 90 percent of satellite obstruction is still quite accurate. More availability of satellite and the geostationary satellites of Beidou has believed to be quite helpful to this situation. It can help the need on measurement like in places with limitation satellite visibility as mentioned above, especially in Indonesia, where millions of parcels still unmeasured and not to mention the huge home work for forest boundary demarcation. Nevertheless, we still need to do the exercise in more areas, and more data acquisitions. And also, we need to investigate the influence of baseline length, etc. when we use RTK GNSS GPS Beidou under heavy obstruction.



REFERENCES

Abdin, H.Z., 2001, Geodesi Satelit, Departemen Teknik Geodesi ITB, PT. Pradnya Paramita, Jakarta.

Abiding, H.Z., 1999, Penentuan Posisi dengan GPS dan Aplikasinya, PT. Pradnya Paramita, Jakarta.

Andreas, H., 2017, Percepatan Pemetaan Persil Menggunakan Teknologi Mobile Base Station (MOBS) RTK Bediou dan RTPPP, Conference Proceeding FIT ISI CGISE 2016, Jogjakarta, Indonesia

Hofmann-Wellenhof, B., Lichtenegger, H. and Walse, E. GNSS Global Navigation Satellite Systems: GPS, GLONASS, Galileo, and More. Springer Verlag 2007, Wien.

Leck A. GPS satellite surveying, 3rd edn 2004. Wiley, New York

Mudita, I., 2011, “GNSS-RTK Network Technology Impact Assessment for Land Surveying at Badan Pertanahan Nasional Republik Indonesia (BPN RI): A Report”, Asian Geospatial Forum: 10th Annual Asian Conference & Exibition on Geospatial Information, Technology & Applications.

Seeber, G 1993, Satellite Geodesy: foundation, method, and applications, Walter de Gruyter, Berlin-New York, C7.