OpenTopography is proud to announce the availability of three new global topographic datasets:
- SRTM GL1 (30m Ellipsoidal) is a version of the popular Shuttle Radar Topography Mission dataset where elevation values are WGS84 ellipsoidal height as opposed to the standard orthometric, or geoid-referenced, elevation. OpenTopography constructed this dataset by subtracting the EGM96 geoid model from the standard SRTM GL1 data. This dataset was produced primarily to support the InSAR community and their need for ellipsoidal referenced DEMs for terrain correction, although we suspect other users may find the dataset valuable.
- ALOS World 3D - 30m is a freely available, downsampled version of a high-resolution (5m) dataset collected by The Japan Aerospace Exploration Agency (JAXA). The ALOS World 3D - 30m dataset is a digital surface model derived from satellite-based stereo-photogrammetry. ALOS World 3D provides data coverage up to 82° latitude (up to 84° in parts of Greenland). This includes a vast part of Antarctica not covered by SRTM. Data quality has also been described as comparable or superior to SRTM  . Another important distinction between the two is that the version of SRTM provided by OpenTopography has most void spaces filled with data from other sources, while ALOS World 3D has not been void-filled, thus SRTM will likely remain the preferred data source for many areas and applications.
Above: Side-by-side comparison of SRTM GL1 (30m Ellipsoidal) and ALOS World 3D datasets over Oahu, Hawaii. Areas shown in green are no data void spaces.
- Our third new dataset, the Global Multi-Resolution Topography (GMRT) Data Synthesis is a bathymetric dataset derived from a collection of multibeam sonar data. The GMRT dataset represents a new and unique workflow on OpenTopography. Data is accessed seamlessly on the OpenTopography site from an external web service. Although the data are sourced from an external service call, users can still perform the typical OpenTopography processing available for rasters, such as creating color-relief and hillshade images, on the selected data.
Above: Side-by-side comparison of SRTM GL1 (30m Ellipsoidal) and GMRT datasets over Oahu, Hawaii. GMRT is lower resolution onshore, but shows considerable bathymetric detail offshore.
SRTM is the most-accessed dataset available through OpenTopography. Close to 48,000 SRTM GL3 (90m) jobs have been submitted by nearly 17,000 users, while over 26,000 SRTM GL1 (30m) jobs have been submitted by 9,000 users. Additionally, the GL1 dataset is used for InSAR terrain correction via the Seamless Synthetic Aperture Radar (SAR) Archive (SSARA) service.
All three of these new datasets, in addition to the previously available SRTM GL1 and GL3 datasets, are available via OpenTopography's RESTful Web Service for global raster data access.