This paper describes the generation of precise digital surface model (DSM) and its validation using the Panchromatic
Remote-sensing Instrument for Stereo Mapping (PRISM) onboard the Advanced Land Observing Satellite (ALOS,
nicknamed "Daichi"), which was successfully launched on January 24, 2006, and has worked very well more than 3.5
years. PRISM performs along-track triplet stereo observations with a forward-, nadir-, and backward-looking radiometer
with 2.5 m ground resolution at nadir in a 35 km-wide swath. It is used to derive a precise DSM or digital elevation
model (DEM) with high spatial resolution. The sensor calibration is very important in achieving the precise DSM
generation using PRISM stereo pair images.
This paper introduces updated calibration results of ALOS optical instruments, focusing on PRISM, and including time
trends of accuracy improvements. We have achieved 7.8 m (RMSE) of absolute geometric accuracy of the PRISM nadirlooking
radiometer. The validation of generated PRISM DSM is shown using reference DSM acquired by airborne Lidar.
The height accuracy of the PRISM DSM has achieved 5.2 m (RMSE). Based on these calibration and validation results,
we also investigate the validation of the global DEM (GDEM) produced by ASTER onboard the TERRA satellite that
was released on June 29, 2009 using generated DSMs by PRISM in terms of global evaluations.