Indonesian National Institute of Aeronautics and Space

This paper presents the implementation of chirp match filtering for Synthetic Aperture Radar (SAR) on a field-programmable gate array (FPGA) using High-Level Synthesis (HLS). HLS enables higher productivity by significantly reducing development time compared to traditional hardware description languages (HDL). A C-based programming approach is employed to leverage parallel processing, which is critical for high-performance signal processing tasks. The design utilizes a symmetric chirp signal as the reference for match filtering, with optimizations implemented through parallelism in the filtering process. Experimental results show that the FPGA-based match filtering, programmed using HLS, achieves low latency and high performance, with a speed increase of 937 times compared to running the same process in Octave on a standard computer.

Mapping data collection through the Real-Time Kinematic (RTK) method provides results with a very high level of accuracy and precision. Currently, various RTK services are available, one of which is RTK based on internet correction, namely Networked Transport of RTCM via Internet Protocol (NTRIP). An accuracy test of the NTRIP-RTK results on UAVs was performed in this study. East Jakarta's Old Shanghai Sedayu City neighborhood served as the location for the aerial photo collection. Using the RTK coordinates of the GNSS antenna on the UAV, the orthorectification process uses the direct georeferencing approach to get the accurate coordinates of each pictures. Eight check points, evenly spaced, are employed and measured with the GNSS geodetic RTK capable device. Utilizing the NTRIP technique, RTK measurements were carried out via the Continuously Operating Reference Stations (CORS) network of the Geospatial Information Agency. In this investigation, position accuracy per photo at the cm-level was nevertheless generated despite the UAV about 7 km distance from the closest CORS. The use of NTRIP-RTK UAV shows a great potential to produce high-accuracy maps. According to the results of accuracy test for the horizontal orthomosaic and vertical on DSM, the accuracy of NTRIP-RTK on UAV is 0.775 m and 0.215 m, respectively. Nevertheless, the NTRIP-RTK UAV is highly sensitive of its environment. In order to provide correction signals from the server to the UAV and the Geospatial Information Agency's CORS network as an accurate reference point, the internet network plays a critical role in NTRIP-RTK accuracy.

Abstract Earthquake (EQ) precursors have been identified from ULF geomagnetic enhancements related to a moderate EQ in Kupang, East Nusa Tenggara, Indonesia. Three components of geomagnetic data (X, Y, and Z) collected during January-June 2010 were analyzed. The EQ occurred on May 7, 2010, and its epicenter was 27.78 km from the KPG Geomagnetic Station. The magnitude and depth of the EQ were 5 and 11.3 km, respectively. This study investigated the energy of ULF geomagnetic signals in the frequency range of 0.03 to 0.04 Hz using SDR based on FFT. The results showed that the geomagnetic energy increased approximately three days before the EQ. Due to the significant magnitude and relative proximity of the EQ to the observation station, it can be concluded that the closer the geomagnetic station from the EQ source, the more likely it is to detect anomalies caused by the EQ. Despite the increase in geomagnetic energy, the Dst index which measures the global activity of the geomagnetic variation in low-latitude regions does not indicate any extraordinary global geomagnetic activity. This indicates that geomagnetic anomalies are most likely related to EQ events.