The Japan Aerospace Exploration Agency (JAXA) generated the global digital elevation/surface model (DEM/DSM) and orthorectified image (ORI) using the archived data of the Panchromatic Remote-sensing Instrument for Stereo Mapping (PRISM) onboard the Advanced Land Observing Satellite (ALOS, nicknamed "<i>Daichi</i>"), which was operated from 2006 to 2011. <br><br> PRISM consisted of three panchromatic radiometers that acquired along-track stereo images. It had a spatial resolution of 2.5 m in the nadir-looking radiometer and achieved global coverage, making it a suitable potential candidate for precise global DSM and ORI generation. In the past 10 years or so, JAXA has conducted the calibration of the system corrected standard products of PRISM in order to improve absolute accuracies as well as to validate the high-level products such as DSM and ORI. <br><br> In this paper, we introduce an overview of the global DEM/DSM dataset generation project, including a summary of ALOS and PRISM, in addition to the global data archive status. It is also necessary to consider data processing strategies, since the processing capabilities of the level 1 standard product and the high-level products must be developed in terms of both hardware and software to achieve the project aims. The automatic DSM/ORI processing software and its test processing results are also described.

ABSTRACT:Topographical information is fundamental to many geo-spatial related information and applications on Earth. Remote sensing satellites have the advantage in such fields because they are capable of global observation and repeatedly. Several satellite-based digital elevation datasets were provided to examine global terrains with medium resolutions e.g. the Shuttle Radar Topography Mission (SRTM), the global digital elevation model by the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER GDEM). A new global digital surface model (DSM) dataset using the archived data of the Panchromatic Remote-sensing Instrument for Stereo Mapping (PRISM) onboard the Advanced Land Observing Satellite (ALOS, nicknamed "Daichi") has been completed on March 2016 by Japan Aerospace Exploration Agency (JAXA) collaborating with NTT DATA Corp. and Remote Sensing Technology Center, Japan. This project is called "ALOS World 3D" (AW3D), and its dataset consists of the global DSM dataset with 0.15 arcsec. pixel spacing (approx. 5 m mesh) and ortho-rectified PRISM image with 2.5 m resolution. JAXA is also processing the global DSM with 1 arcsec. spacing (approx. 30 m mesh) based on the AW3D DSM dataset, and partially releasing it free of charge, which calls "ALOS World 3D 30 m mesh" (AW3D30). The global AW3D30 dataset will be released on May 2016. This paper describes the processing status, a preliminary validation result of the AW3D30 DSM dataset, and its public release status. As a summary of the preliminary validation of AW3D30 DSM, 4.40 m (RMSE) of the height accuracy of the dataset was confirmed using 5,121 independent check points distributed in the world.

We investigate the temperature dependences of the Brillouin scattering properties in a perfluorinated graded-index (PFGI-) polymer optical fiber (POF) in a wide temperature range from −160 to 125 °C. The temperature dependences of the Brillouin frequency shift, linewidth, and Stokes power are almost linear at lower temperature down to −160 °C; while they show nonlinear dependences at higher temperature. These behaviors appear to originate from the partial glass transition of the polymer material.

We investigated the Brillouin gain spectrum dependence on large strain of up to 60% in a polymer optical fiber (POF) at 1.55 μm, and found that the Brillouin frequency shift (BFS) abruptly changes from ∼2.7 GHz to ∼3.2 GHz. We named this phenomenon “BFS hopping,” and found it to originate from the varied acoustic velocity induced by the stepwise change in the core diameter of the POF. This is because of the yielding of the overcladding layer composed of polycarbonate. After the occurrence of BFS hopping phenomenon, the BFS dependence coefficients on strain and temperature in the POF were measured to be −65.6 MHz/% and −4.04 MHz/K respectively. These values indicate that, compared to an unstrained POF, further higher-precision temperature sensing with lower strain sensitivity is feasible.

We perform a pilot trial of the highly convenient taper fabrication of perfluorinated graded-index polymer optical fibers. Instead of conventional external heating, we utilize internal heating caused by high-power propagating light (500 mW in this experiment). An approximately 4-mm-long section of a polymer fiber is tapered, and the outer diameter of the >2-mm-long waist around its midpoint is approximately 200 µm, which is quite uniform with a standard deviation of 4.3 µm. The polymer fiber taper fabricated by this technique is shown to be capable of generating evanescent waves and thus measuring the refractive indices of liquids from 1.333 to 1.410.