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Journal of Global Positioning Systems Vol. 22, No. 1, 2026 |
Cover |
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Journal of Global Positioning Systems
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JGPS Team Structure, Copyright and Table of Contents |
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JGPS Team Structure, Copyright
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1. Advances in Real-Time GNSS Monitoring of Earthquakes and Volcanoes in Indonesia |
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Muhammad Al Kautsar, Moh. Fifik Syafiudin, Rahmat Triyono, Priatin Hadi Wijaya, Oktadi Prayoga, Sulistiyani, Ayu Nur Safi’i, Thomas Hardy, Ajat Sudrajat,Fanny Zafira Mukti
Indonesia is among the most tectonically and volcanically active regions worldwide, where frequent earthquakes, volcanic eruptions, and long-term surface deformation pose serious risks to population centers and critical infrastructure. Reliable real-time geodetic monitoring is therefore essential for hazard assessment, early warning, and disaster mitigation. This study presents the status and recent advances in GNSS-based real-time geohazard monitoring in Indonesia, with an emphasis on precise point positioning with ambiguity resolution (PPP-AR) implemented through the GSeisRT real-time engine. GSeisRT processes 1 Hz multi-GNSS observations and generates low-latency regional satellite clock and phase bias products, enabling stable and high-precision real-time displacement monitoring. GSeisRT has been deployed within the nationwide Ina-CORS network operated by the BIG and supports continuous monitoring of earthquakes, volcanic deformation, land subsidence, and active faults. Several recent seismic events, including the 2023 Banda Sea Mw 7.1 earthquake and subsequent Mw 5.8-6.6 events, were successfully captured in real time. The derived coseismic displacements and peak ground displacements (PGDs) allow rapid earthquake magnitude determination that agrees well with estimates published by the United States Geological Survey (USGS). Performance comparisons with existing real-time PPP systems demonstrate that GSeisRT provides improved robustness and continuity, effectively suppressing spurious position jumps caused by incorrect ambiguity resolution. Additional developments, including the integration of GNSS with collocated accelerometer data and the availability of global 1 Hz real-time satellite products, further enhance short-period deformation monitoring and seismic response capability. Although challenges remain due to sparse station spacing and communication limitations in remote areas, the results confirm that advanced re-al-time GNSS technologies provide a reliable and scalable foundation for strengthening geohazard early warning and resilience in Indonesia.
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2. Flood Detection Using CYGNSS GNSS-R Observations - A Case Study of the 2022 Sindh Flood, Pakistan |
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Afaq Karim, Dongkai Yang1, Omada Friday Ojonugwa
Flood monitoring and mapping are essential
for effective disaster response, particularly in regions
frequently affected by extreme rainfall events.
Conventional flood detection methods are often
constrained by high costs, cloud cover, and limited
temporal resolution. This study investigates the
capability of Global Navigation Satellite System
Reflectometry (GNSS-R) for flood detection using
Level-1 data from the Cyclone Global Navigation
Satellite System (CYGNSS) during the severe August
2022 flood event in Sindh Province, Pakistan. Surface
reflectivity was estimated using a bistatic radar
formula, in which the corrected signal-to-noise ratio
(SNRc) was derived as a proxy for surface water
presence after quality control, incidence-angle
filtering, and outlier removal. To generate continuous
flood reflectivity fields from irregular CYGNSS
observations, a Natural Neighbor interpolation
technique based on Voronoi tessellation was applied.
Flooded areas were identified using an empirically
derived SNRc threshold of approximately 16 dB,
determined from observations over permanent water
bodies. The resulting CYGNSS-derived flood maps
show strong spatial agreement with MODIS-based
flood inundation maps. The overall accuracy achieved
is 0.819, indicating that approximately 82% of the
MODIS and CYGNSS grid cells were correctly
classified.
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| To Be Completed |
Back Cover |
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Journal of Global Positioning Systems
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