Evaluation of accuracy and availability of GNSS Satellite-Based Augmentation Services in Thailand GPS/GNSS GPS/GNSS Monsak Socharoentum and Wasan Pattara-Atikom National Electronics and Computer Technology Center, THAILAND ms@nectec.or.th wasan@nectec.or.th October 13, 2016

With SBAS: Positioning Accuracy 10  2 meters Corrections Corrections Raw measurements Accuracy 10 meters  1-2 meters http://www.novatel.com/assets/images/_resampled/ResizedImage500279-SBAS-image.jpg

SBAS coverage in the world WAAS (USA) EGNOS (Europe) MSAS (Japan) GAGAN (India) SDCM (Russia) BDSBAS (China) Thailand Anyway, are SBAS signals also useful for others (such as Thailand)? If so, how is the positioning accuracy performance?

Research questions and experiment setting “Does and how SBAS improve GNSS positioning accuracy in Thailand?”, “What is the performance of operational SBAS and experimental SBAS?”, and “If SBAS is used for vehicle tracking, what is the behavior of the vehicle positions?”

Table 1. Experiment setting Test Comparison Pair Static Existing vs. experimental SBAS Vehicle tracking GPS vs. GPS+QZSS SBAS RTK Positioning Figure 3. (a) QZSS prototype receiver, (b) u-blox receiver, (c) installation locations

Reference Point Setup Spacial thanks to RTK Survey 1-2 cm. accuracy Then all four receivers were placed on the top of the pole Data collection period was 10 minutes Spacial thanks to TOPCON Thailand supports survey grade receivers Department of Land, Thailand supports RTK VRS account

GNSS Receiver Specifications Huawei P7 L10 Prototype QZSS receiver ublox EVK M6N GNSS Receivers GPS (USA) GLONASS (Russia) GNSS Constellations GPS (USA) GPS (USA) SBAS No Yes (QZSS) Yes (MSAS)

Plot of positions in static test Table 2. Circular Error Probable (CEP 95%) and Root-Mean-Square-Error (RMSE) Plot of positions in static test  Receivers CEP (meters) RMSE (meters) GNSS SBAS function Android smart phone 9.19 5.28 GPS+ GLONASS N/A Prototype QZSS receiver 5.36 3.66 GPS QZSS u-blox receiver 2.02 1.90 MSAS

Precision Accuracy Circular Error Probable 95% (meters) Root Mean Squared Error (meters) Circular Error Probable 95% (meters) Huawei 9.19 QZSS 5.36 ublox 2.02 No SBAS SBAS SBAS

Bus tracking with and w/o SBAS (non urban canyons areas) Red: GPS + QZSS augmentation Blue: GPS w/o augmentation

Spatial position deviations in urban canyons

Satellites availability tracked by QZSS prototype receiver Inbound Satellites availability tracked by QZSS prototype receiver Outbound 0-3:  Red 4-8: Yellow >=9: Green Inbound

Effect of poor signal availability in urban canyons

Conclusion correction information generated from Japan can significantly improve the accuracy of GPS positioning in Thailand. 2 meters CEP 95% is possible to be achieved Vehicle tracking: Positions from SBAS can be used for detecting a particular traffic lane that the vehicle is moving along including the course of transition such as U-turn.

Acknowledgement We are gratefully appreciated the company/organization below for their kindly supports. TOPCON Thailand supports high-end GNSS receiver and two technicians for RTK operation. Department of Land, Ministry of Internal Affair, Thailand supports RTK VRS account HONDA Motor Japan supports the QZSS prototype receiver. JAXA optimizes and broadcast QZSS’s correction information.