The ASTER Orthorectified Registered Radiance at the Sensor (AST14OTH) product (https://lpdaac.usgs.gov/documents/618/ASTER_Earthdata_Search_Order_Instructions.pdf) contains imagery transformed from a perspective projection to an orthogonal one. An orthorectified image possesses the geometric characteristics of a map with near-vertical views for every location. These products are terrain corrected, provide radiometrically calibrated radiance, and are mapped to the Universal Transverse Mercator (UTM) coordinate system. The spatial resolution is 15 m (VNIR), 30 m (SWIR), and 90 m (TIR) with a temporal coverage of 2000 to present.

The inputs include the following: an ASTER Level 1A Reconstructed Unprocessed Instrument dataset; georeferencing information from the ASTER instrument's and Terra platform's ephemeris and attitude data; and an ASTER-derived digital elevation model (DEM). The output product includes fifteen orthorectified ASTER Level 1B calibrated radiance images, one per band, as listed below.

Improvements/Changes from Previous Versions

As of January 2021, the LP DAAC has implemented version 3.0 of the Sensor Information Laboratory Corporation ASTER DEM/Ortho (SILCAST) software, which is used to generate the Level 2 on-demand ASTER Orthorectified and Digital Elevation Model (DEM) products (AST14). The updated software provides digital elevation extraction and orthorectification from ASTER L1B input data without needing to enter ground control points or depending on external global DEMs at 30-arc-second resolution (GTOPO30). It utilizes the ephemeris and attitude data derived from both the ASTER instrument and the Terra spacecraft platform. The outputs are geoid height-corrected and waterbodies are automatically detected in this version. Users will notice differences between AST14DEM, AST14DMO, and AST14OTH products ordered before January 2021 (generated with SILCAST V1) and those generated with the updated version of the production software (version 3.0). Differences may include slight elevation changes over different surface types, including waterbodies. Differences have also been observed over cloudy portions of ASTER scenes. Additional information on SILCAST version 3.0 can be found on the SILCAST website (http://www.silc.co.jp/en/products.html).

Starting June 23, 2021, radiometric calibration coefficient Version 5 (RCC V5) will be applied to newly observed ASTER data and archived ASTER data products. Details regarding RCC V5 are described in the following journal article.

Tsuchida, S., Yamamoto, H., Kouyama, T., Obata, K., Sakuma, F., Tachikawa, T., Kamei, A., Arai, K., Czapla-Myers, J.S., Biggar, S.F., and Thome, K.J., 2020, Radiometric Degradation Curves for the ASTER VNIR Processing Using Vicarious and Lunar Calibrations: Remote Sensing, v. 12, no. 3, at https://doi.org/10.3390/rs12030427.