ESTIMASI DAERAH POTENSI PENANGKAPAN IKAN BERDASARKAN PENDEKATAN KESESUAIAN AREA THERMAL FRONT DAN AREA MESOTROPIK

Research in Potential Fishing Zone (PFZ) has undergone many developments, including parameter suitability selection. The thermal front has become the primary parameter input of ZPPI (LAPAN's PFZ). The accuracy of the thermal front parameter to predict PFZ cannot be known with certainty because of the radius between ZPPI with fishing areas, so it is necessary to develop parameters to support the thermal front. The thermal front described the meeting area of two water masses with different temperature characteristics associated with high nutrients (chlorophyll-a) and indicate an upwelling's appearance. This study aims to determine ZPPI by approaching the thermal front and mesotrophic area's matching area (chlorophyll-a concentration 0.2-0.5 mg/m3). Chlorophyll-a and sea surface temperature data for thermal fronts detection are derived from Aqua MODIS satellite on Google Earth Engine (GEE). The matching area's approach between the thermal front and mesotrophic area is used in the analysis of ZPPI. The results show thermal front and mesotrophic area on WPPNRI 715 have a variation seasonally where December appears like the peak event. The two parameters are distributed evenly from coastal areas to high seas. This method generates thermal fronts that have more than 60.3% matching with the mesotrophic area where the amount is acceptable due to has more than 50% amount of moderate ZPPI. The accuracy improvement in ZPPI both on the coast and open sea can be determined through this approach.Zona potensi penangkapan ikan (ZPPI) telah mengalami banyak pengembangan salah satunya adalah pemilihan kesesuaian parameter. Thermal front telah menjadi parameter utama dalam input informasi ZPPI LAPAN. Akurasi informasi thermal front yang digunakan sebagai input ZPPI tidak dapat diketahui dengan pasti signifikansinya karena faktor jarak informasi titik ZPPI terhadap lokasi tangkapan sehingga diperlukan pengembangan parameter untuk mendukung informasi thermal front tersebut. Thermal front merupakan daerah pertemuan dua massa air yang memiliki karakteristik suhu yang berbeda dan mengindikasikan kemunculan upwelling. Penelitian ini bertujuan untuk menentukan daerah potensi penangkapan ikan dengan pendekatan kesesuaian area thermal front dengan area mesotropik (konsentrasi klorofil-a 0,2-0,5 mg/m3). Data klorofil-a untuk deteksi area mesotropik dan suhu permukaan laut untuk thermal front berasal dari satelit Aqua MODIS di Google Earth Engine (GEE). Metode kesesuaian thermal front terhadap area mesotropik digunakan dalam analisis daerah potensi penangkapan ikan. Hasil penelitian menunjukkan bahwa thermal front dan area mesotropik di WPPNRI 715 memiliki variasi terhadap musim, dengan bulan Desember sebagai puncak kejadian. Kedua parameter tersebut terdistribusi secara merata mulai dari area pesisir hingga laut lepas. Dari metode ini didapatkan thermal front yang memiliki kesesuaian area (bertampalan) terhadap area mesotropik sebesar 60,3%. Selain itu kelas ZPPI dengan tingkat kepercayaan tinggi memiliki jumlah lebih dari 50% ZPPI moderate, dimana jumlah tersebut sesuai ambang batas yang dapat diterima. Sehingga peningkatan akurasi lokasi ZPPI baik di pesisir maupun laut lepas dapat ditentukan melalui pendekatan ini

Plate and faults boundary detection using gravity disturbance and Bouguer gravity anomaly from space geodesy

Nowadays, satellite technology has developed significantly. Geodesy satellites such as Grace and Grace-FO can be used for subsurface mapping. The mapping is in the form of detection of the plate details, faults, and regional geodynamic conditions. This study aims to detect plate and faults from space geodesy using the gravity disturbance and Bouguer gravity anomaly parameter. The study area is in the Sunda Strait. Gravity disturbance is one of the gravity model parameters. Gravity disturbance is the gravitational potential of the topography expressed by the spherical harmonic model and the topographic effect by Barthelmes's calculations. Gravity disturbance can visualize subsurface conditions. Bouguer gravity anomaly is needed to get the condition on subsurface objects. This parameter visualizes subsurface conditions in the form of rocks and non-rocks. These conditions can distinguish oceanic crust and continental crust. Gravity contours are needed to obtain plate and faults predictions. The results obtained are validated patterns and shapes with plate and faults secondary data. The tolerance used in this validation is 80%. The gravity disturbance parameter obtained a value of 83% in verifying the accuracy of assessment in plate and faults detection. The Bouguer gravity disturbance parameter obtained a verification value of accuracy assessment in plate detection but 65% in faults detection. This accuracy assessment uses pattern and texture parameters in detecting the similarity of two or more images. This plate and faults detection results are more detailed and can be used for geophysical, geological, earthquake, and earth dynamics applications

Association Study Between Thermal Front Phenomena and Bali Sardinella Fishing Areas in Bali Strait

Thermal front has been widely used as a parameter for determining fishing zones. Tis study aimed to  determine  the  thermal  front  distribution  and  to  analyze  its  association  with  the  Bali  Sardinella  fishing zones  in  the  Bali  Strait.  Termal  front  generated  using  sea  surface  temperature  (SST)  from  Aqua  MODIS imagery. Meanwhile, the fishing point data of Bali Sardinella were collected to validate our analysis results. Te data were analyzed into Spatio-temporal information. Te main facts that stand out are that the thermal front  was  predominantly  found  in  the  peak  of  first (April)  and  second  (September)  transitional  season, which was the peak season for the thermal front to occur in a year. Te least of the thermal front occurred in the  South-west  monsoon.  Te  linear  relationship  was found  when  the  peak  of  thermal  front  occurrence compared to the number of catch yields. Based on matching distance analysis, the maximum distance used (twenty  kilometres  buffer)  show  36  matching  points from  101  data  compared  or  at  range  35.6%.  In conclusion, there is a linear relationship between the thermal front parameter and catch yield. It is still used to predict the fishing zone, even though the correlation is not significantly found

Current land subsidence in Jakarta: a multi-track SBAS InSAR analysis during 2017–2022 using C-band SAR data

In Jakarta, Indonesia, rapid urbanization and intensive groundwater extraction have led to significant land subsidence, posing challenges for sustainable urban management. This study utilized Interferometry Synthetic Aperture Radar (InSAR) integrated with multi-track data analysis to generate refined time-series and velocities of 2D displacement across Greater Jakarta. This study reveals notable variation in subsidence rates across different areas, with the most significant subsidence observed in Cikarang and the coastal regions of North Jakarta, which remains linear to this day. Notably, while the 2D approach improved accuracy by up to 53% at some locations, discrepancies at others indicated that simpler descending projections might sometimes yield better results. This underscores the necessity for a nuanced application of geodetic methods based on specific site conditions to effectively monitor and manage land subsidence in complex urban environments. Our findings highlight the critical importance of integrating multiple monitoring approaches to comprehensively address both vertical and horizontal displacement

Assessing land subsidence from anthropogenic activity in Northern Sumatra, Indonesia revealed using SAR interferometry

Land subsidence is a significant issue in urban areas globally, including several cities with a growing population in Northern Sumatra, Indonesia. This study employs Sentinel-1 SAR data and the Small Baseline Subset (SBAS) InSAR technique to monitor land subsidence in Medan, Deli Serdang, Dumai, North Aceh, and Lhokseumawe from 2015 to 2023. The SBAS algorithm was implemented in LiCSBAS with an unwrapped interferogram. Then corrected for atmospheric effects using GACOS, was employed to increase the results of the land subsidence. The analysis was enhanced using GRACE satellite data to assess the impact of groundwater depletion on subsidence. Results indicate significant subsidence across all study regions, particularly in Medan and Dumai, with rates ranging from -48.6 mm/year to +54.1 mm/year. The findings highlight the critical role of rapid urbanization, excessive groundwater extraction, and oil and gas exploration in driving subsidence. This study underscores the need for sustainable urban planning and aquifer management to mitigate future environmental and infrastructural risks