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In 2016, the first processing of the semi-global digital surface models (DSMs) utilizing all the archives of stereo imageries derived from the Panchromatic Remote sensing Instrument for Stereo Mapping (PRISM) onboard the Advanced Land Observing Satellite (ALOS) was successfully completed. The dataset was freely released to the public in 30 m grid spacing as the 'ALOS World 3D - 30m (AW3D30)', which was generated from its original version processed in 5 m or 2.5 m grid spacing. The dataset has been updated since then to improve the absolute/relative height accuracies with additional calibrations. However, the most significant update that should be applied for improving the data usability is the filling of void areas, which correspond to approx. 10% of semiglobal coverage, mostly due to cloud covers. In 2020, we completed the filling process by using other open-access digital elevation models (DEMs) such as Shuttle Radar Topography Mission (SRTM) DEM, Advanced Spaceborne Thermal Emission and Reflection Radiometer Global DEM (ASTER GDEM), ArcticDEM, etc., except for Antarctica. In this paper, we report on the filling process of the remaining voids in Antarctica by using other open-access DEMs such as Reference Elevation Model of Antarctica (REMA) DSM, TerraSAR-X add-on for Digital Elevation Measurement (TanDEM-X, TDX) 90m DEM, and ASTER GDEM to complete the void-free semi-global AW3D30 datasets. [ABSTRACT FROM AUTHOR]

In 2016 we first completed the global data processing of digital surface models (DSMs) by using the whole archives of stereo imageries derived from the Panchromatic Remote sensing Instrument for Stereo Mapping (PRISM) onboard the Advanced Land Observing Satellite (ALOS). The dataset was freely released to the public in 30 m grid spacing as the 'ALOS World 3D - 30m (AW3D30)', which was generated from its original version processed in 5 m or 2.5 m grid spacing. The dataset has been updated since then to improve the absolute/relative height accuracies with additional calibrations. However the most significant update that should be applied for improving the data usability is the filling of void areas, which correspond to approx. 10% of global coverage, mostly due to cloud covers. In this paper we introduce the updates of AW3D30 filling the voids with other open-access DSMs such as Shuttle Radar Topography Mission (SRTM) Digital Elevation Model (DEM), Advanced Spaceborne Thermal Emission and Reflection Radiometer Global DEM (ASTER GDEM), ArcticDEM, etc., through inter-comparisons among these datasets. [ABSTRACT FROM AUTHOR]

With the launch of the Advanced Land Observing Satellite (ALOS) in 2006, the Japanese Space Agency (JAXA) took the initiative to implement the first global-scale systematic acquisition strategy for satellite sensors at fine and medium (2.5–20 m) spatial resolution. Comprising all three sensors on ALOS (PALSAR, PRISM, AVNIR-2), the plan was designed to serve all ALOS user categories and aimed at producing spatially and temporally consistent baseline coverages over the planet on a repetitive basis, to accommodate systematic global-scale, fine-resolution, monitoring of the environment. Unlike the common background missions defined for most fine-resolution Earth Observation satellites, the observation strategy was implemented as a top-level foreground mission with a priority second only to that of special observation requests and emergency observations and sensor calibration. While the ALOS mission regrettably ended in April 2011, the global acquisition strategy nevertheless produced a comprehensive and homogeneous global archive in which consistent time-series of data are available for any arbitrary land area on Earth (excluding Antarctica > 77.5° South latitude, which could not be reached by the sensors). Clouds and haze inevitably constituted limitations for the optical sensors, while for the PALSAR instrument, two cloud-free and near-gap free (~ 95%) global coverages were achieved annually during the 4.5 years in operations. Previously, such uniform data archives existed only for coarse-resolution sensors such as AVHRR, MERIS and MODIS. The ALOS BOS supported a variety applications from local to global scales, ranging from structural deformation, monitoring of wetlands regional inundation patterns and mapping of forest extent and changes over nations and continents at spatial resolutions as fine as 10 m. The Advanced Land Observing Satellite 2 (ALOS-2) was launched on May 24, 2014. Equipped with an enhanced L-band SAR sensor (PALSAR-2), ALOS-2 resumes the global wall-to-wall acquisitions to assure continuity and consistency with JAXA’s global mission objectives and unique L-band SAR archive created by ALOS PALSAR. [ABSTRACT FROM AUTHOR]