Pemanfaatan Persistent Scatterer Interferometry Synthetic Aperture Radar (PSInSAR) Untuk Mengidentifikasi Laju Deformasi Permukaan di Lapangan Panas Bumi Ulubelu

Lapangan panas bumi Ulubelu telah diekstraksi sejak tahun 2012 dengan menghasilkan 2 x 55 MW dari PLTP unit 1 & 2 dan meningkat menjadi 4 x 55 MW sejak tahun 2016 dengan beroperasinya unit 3 dan unit 4. Peningkatan eksploitasi energi panas bumi di Ulubelu berpotensi menimbulkan perubahan kondisi geologi dan lingkungan yang salah satunya adalah subsiden. Penelitian ini bertujuan untuk mengidentifikasi potensi laju deformasi permukaan memanfaatkan metode Persistent Scatterer Interferometry Synthetic Aperture Radar (PSInSAR) di lapangan panas bumi Ulubelu. Sebanyak 49 data Sentinel-1 periode Oktober 2014 hingga Maret 2020 dengan mode descending telah diolah dan dianalisis menggunakan tiga software utama yaitu SNAP, StaMPS dan StaMPS-Visualizer. Pembentukan interferogram pada setiap pasangan data (image pair) antara master dengan seluruh slave dilakukan menggunakan SNAP. Seluruh data interferogram kemudian diexport sebagai input data StaMPS untuk mendapatkan nilai piksel yang memiliki koherensi terbaik dan persistent. Hasil pengolahan menunjukkan laju deformasi per titik persistent scatterer (PS) berkisar antara -7,3 hingga +7,5 mm/tahun relatif pada arah Line of Sight (LOS) tanpa validasi lapangan. Pola deformasi berupa penurunan muka tanah berada di sekitar area eksploitasi panas bumi, sedangkan kenaikan muka tanah (uplift) terdeteksi di luar area eksploitasi. Hasil analisis menunjukkan bahwa kesamaan laju deformasi pada PLTP unit 1 & 2 dengan PLTP unit 3 & 4 mengindikasikan proses subsiden di area Ulubelu didominasi oleh proses ekstraksi fluida panas bumi. Temuan ini juga memperkuat penelitian sebelumnya yang menunjukkan bahwa proses subsiden di area panas bumi Ulubelu disebabkan oleh pemadatan batuan alterasi.

Processing methodology for the ITS_LIVE Sentinel-1 ice velocity product

The NASA MEaSUREs Inter-mission Time Series of Land Ice Velocity and Elevation (ITS_LIVE) project seeks to accelerate understanding of critical glaciers and ice sheet processes by providing researchers with global, low-latency, comprehensive and state-of-the-art records of surface velocities and elevations as observed from space. Here we describe the image-pair ice velocity product and processing methodology for ESA Sentinel-1 radar data. We demonstrate improvements to the core processing algorithm for dense offset tracking, “autoRIFT”, that provides finer resolution and higher accuracy data products with improved computational efficiency when compared to earlier versions. A novel calibration is applied to the data to correct for Sentinel-1A/B subswath- and full swath-dependent geolocation errors caused by systematic issues with the instruments. Sentinel-1’s C-band images are affected by variations in the total electron content of the ionosphere that results in large velocity errors in the azimuth (along-track) direction. To reduce these effects slant-range (line-of-sight or LOS) velocities are used and accompanied by LOS parameters that support map coordinate (x/y) velocity inversion from ascending and descending slant-range offset measurements, as derived from 2 image-pairs. The described product and methods comprise the MEaSUREs ITS_LIVE Sentinel-1 Image-Pair Glacier and Ice Sheet Surface Velocities: Version 2 (https://its-live.jpl.nasa.gov).

A Multi-view Camera Model for Line-Scan Cameras with Telecentric Lenses

We propose a novel multi-view camera model for line-scan cameras with telecentric lenses. The camera model supports an arbitrary number of cameras and assumes a linear relative motion with constant velocity between the cameras and the object. We distinguish two motion configurations. In the first configuration, all cameras move with independent motion vectors. In the second configuration, the cameras are mounted rigidly with respect to each other and therefore share a common motion vector. The camera model can model arbitrary lens distortions by supporting arbitrary positions of the line sensor with respect to the optical axis. We propose an algorithm to calibrate a multi-view telecentric line-scan camera setup. To facilitate a 3D reconstruction, we prove that an image pair acquired with two telecentric line-scan cameras can always be rectified to the epipolar standard configuration, in contrast to line-scan cameras with entocentric lenses, for which this is possible only under very restricted conditions. The rectification allows an arbitrary stereo algorithm to be used to calculate disparity images. We propose an efficient algorithm to compute 3D coordinates from these disparities. Experiments on real images show the validity of the proposed multi-view telecentric line-scan camera model.

Real-Time FPGA Accelerated Stereo Matching for Temporal Statistical Pattern Projector Systems

The presented paper describes a hardware-accelerated field programmable gate array (FPGA)–based solution capable of real-time stereo matching for temporal statistical pattern projector systems. Modern 3D measurement systems have seen an increased use of temporal statistical pattern projectors as their active illumination source. The use of temporal statistical patterns in stereo vision systems includes the advantage of not requiring information about pattern characteristics, enabling a simplified projector design. Stereo-matching algorithms used in such systems rely on the locally unique temporal changes in brightness to establish a pixel correspondence between the stereo image pair. Finding the temporal correspondence between individual pixels in temporal image pairs is computationally expensive, requiring GPU-based solutions to achieve real-time calculation. By leveraging a high-level synthesis approach, matching cost simplification, and FPGA-specific design optimizations, an energy-efficient, high throughput stereo-matching solution was developed. The design is capable of calculating disparity images on a 1024 × 1024(@291 FPS) input image pair stream at 8.1 W on an embedded FPGA platform (ZC706). Several different design configurations were tested, evaluating device utilization, throughput, power consumption, and performance-per-watt. The average performance-per-watt of the FPGA solution was two times higher than in a GPU-based solution.

Quality Assurance of Image Registration Using Combinatorial Rigid Registration Optimization (CORRO)

Purpose: Expert selected landmark points on clinical image pairs to provide a basis for rigid registration validation. Using combinatorial rigid registration optimization (CORRO) provide a statistically characterized reference data set for image registration of the pelvis by estimating optimal registration. Materials ad Methods: Landmarks for each CT/CBCT image pair for 58 cases were identified. From the landmark pairs, combination subsets of k-number of landmark pairs were generated without repeat, forming k-set for k=4, 8, and 12. A rigid registration between the image pairs was computed for each k-combination set (2,000-8,000,000). The mean and standard deviation of the registration were used as final registration for each image pair. Joint entropy was used to validate the output results. Results: An average of 154 (range: 91-212) landmark pairs were selected for each CT/CBCT image pair. The mean standard deviation of the registration output decreased as the k-size increased for all cases. In general, the joint entropy evaluated was found to be lower than results from commercially available software. Of all 58 cases 58.3% of the k=4, 15% of k=8 and 18.3% of k=12 resulted in the better registration using CORRO as compared to 8.3% from a commercial registration software. The minimum joint entropy was determined for one case and found to exist at the estimated registration mean in agreement with the CORRO algorithm. Conclusion: The results demonstrate that CORRO works even in the extreme case of the pelvic anatomy where the CBCT suffers from reduced quality due to increased noise levels. The estimated optimal registration using CORRO was found to be better than commercially available software for all k-sets tested. Additionally, the k-set of 4 resulted in overall best outcomes when compared to k=8 and 12, which is anticipated because k=8 and 12 are more likely to have combinations that affected the accuracy of the registration.