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All Journal Journal of Geoscience, Engineering, Environment, and Technology Jurnal Geologi dan Sumberdaya Mineral (Journal of Geology and Mineral Resources)
Roviansah, Mohamad
Unknown Affiliation
Chemistry Earth & Planetary Sciences Energy Engineering Environmental Science Physics

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Preliminary Result on Optimum Seed Generation Bandwidth for Object-Based Image Segmentation (OBIS) of Porphyritic Igneous Thin Sections Nugroho, Rio Priandri; Widjaya, Victoria Vania Blanca; Roviansah, Mohamad
Jurnal Geologi dan Sumberdaya Mineral Vol. 25 No. 1 (2024): JURNAL GEOLOGI DAN SUMBERDAYA MINERAL
Publisher : Pusat Survei Geologi

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.33332/jgsm.geologi.v25i1.698

Abstract

Crystal size distribution (CSD) analysis is one of many methods for studying the crystallization history of magma. It involves labor-intensive digitation of all crystals, which may prolong the processing of large data sets. This study presents a preliminary result of Object-Based Image Segmentation (OBIS) as a semi-automatic approach in crystal digitation. Five data sets containing 9 photomicrographs of porphyritic igneous rock thin sections were processed using SAGA GIS. The procedure produced an optimum bandwidth equation of y = 38.455 ln(x) + 114, where x is the average size of sampled crystal in mm. Segmentation tests on another sample using the formula returned good and consistent results with important notes on sensitivity to textures which may result in crystal segment separation, such as fractures, veins, and sieve, as well as the inability to separate all groundmass crystals. Even though it shows good results, this formula only applies where the pixel-to-length conversion factor of 562.2 pixel/mm. Keywords: OBIS, SAGA GIS, Optimum bandwidth, Photomicrograph, Porphyritic igneous rock thin section.
Landslide Susceptibility Mapping Using Logistic Regression Methods in Bogor Regency Assyidiqi, Sutan Vasya; Roviansah, Mohamad; Sujaka, Muhammad 'Azza; Nugroho, Rio Priandri; Misbahudin
Journal of Geoscience, Engineering, Environment, and Technology Special Issue from The 2nd International Conference on Upstream Energy Technology and Digitalization
Publisher : UIR PRESS

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.25299/jgeet.2025.10.1.1.24273

Abstract

Landslides are a recurrent hazard in Bogor Regency, where steep volcanic terrain, high rainfall, varied lithology, land-use changes and active faults contribute to slope instability. This study presents the first regency-wide landslide susceptibility model using Logistic Regression supported by field validation. A dataset of 220 landslide occurrences from 2017 to 2022 and multiple geospatial factors including rainfall, slope, lithology, landcover, and NDVI was analyzed using a 70:30 train–test split to generate coefficient weights, probability surfaces and a binary susceptibility map derived from ROC-AUC thresholds. Landcover shows the strongest positive influence on landslide occurrence, whereas NDVI has the strongest negative effect, reflecting the stabilizing role of vegetation. Fault proximity exhibits near-zero influence, likely due to inactive structures or limited spatial resolution. The model achieved 82 percent accuracy with an AUC of 0.86. Susceptibility clustering near historical data suggests possible inventory bias. Improving model reliability will require more evenly distributed landslide data and UAV-based mapping to detect vegetation-covered past landslides.
Co-Authors Assyidiqi, Sutan Vasya Misbahudin Nugroho, Rio Priandri Sujaka, Muhammad 'Azza Widjaya, Victoria Vania Blanca