tanbul 2004
CALIBRATION AND VALIDATION OF PRISM ONBOARD ALOS
T. Tadono™ *, M. Shimada“, M. Watanabe ®, T. Hashimoto ®, T. Iwata ®
* Earth Observation Research and Application Center (EORC), Japan Aerospace Exploration Agency (JAXA),
Harumi Triton X-23F, 1-8-10 Harumi, Chuo-ku, Tokyo 104-6023 Japan — tadono.takeo@jaxa.jp
? ALOS Project Team, Japan Aerospace Exploration Agency (JAXA), 2-1-1, Sengen, Tsukuba, Ibaraki 305-8505 Japan
KEY WORDS: Calibration, Geometric, Accuracy, Stereoscopic, DEM/DTM, Remote Sensing
ABSTRACT:
This paper introduces the updated plans for sensor calibration and product validation of the Panchromatic Remote-sensing
Instrument for Stereo Mapping (PRISM), which is to fly on the Advanced Land Observing Satellite (ALOS) satellite that will be
launched this Japanese fiscal year. PRISM is used to derive digital elevation models (DEMs) with very high spatial resolution,
which is also one of the objectives of the ALOS mission. To achieve this objective, PRISM consists of three panchromatic
radiometers for forward-, nadir-, and backward-looking in the along-track direction, and acquires the images in the same orbit and at
almost the same time. The geometric calibration is important in generating a highly accurate DEM with high spatial resolution by
using PRISM's triplet images. Highly accurate ground control points (GCP) are necessary to calibrate the geometric accuracy and
validate the generated DEM. Collecting GCP worldwide is difficult and hard work in spite of its importance.
In this paper, we describe the current plans for calibrating and validating PRISM aboard the ALOS, and in particular, our strategies
for preparing GCP with evaluation items for geometric calibration, including expected problem effects regarding geometric accuracy.
1. INTRODUCTION
The Advance Land Observing Satellite (ALOS) is the next
Japanese Earth observation satellite, and will be launched
within this fiscal year. The mission objectives of the ALOS are
: ; s Backward
cartography, regional observation, disaster monitoring, etc. In Swath width
particular, geographic information such as clevation, topogra- 35km
e
phy, land use, and land cover, are necessary as basic informa-
tion in many fields of practical applications and research areas.
However, only just under 30% of the terrestrial area has been
covered by 1:25,000 scale topographic maps worldwide. To
achieve the mission objectives, ALOS has three mission
instruments, two optical sensors called PRISM and AVNIR-2,
and an L-band Synthetic Aperture Radar called PALSAR.
PRISM stands for the Panchromatic Remote-sensing Instrument
Forward
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for Stereo Mapping and consists of three independent Pointing Coverage 70km
radiometers for nadir, forward, and backward directions. It will PN
scan far Genorah ; :oifal Elovat; > S ji = 2
be used for generating a Digital Elevation Model E Sub satellite tmck
high spatial resolution. The development statuses of the S .. Figure 1. Observation geometry of triplet mode
and its instruments were represented by Ichitsubo et al. (2003)
and Matsumoto et al. (2003).
This paper introduces the updated plans for sensor calibration
and product validation of the PRISM, in particular strategies of
preparing the ground control points (GCPs) including expected
problems based on pre-flight testing of PRISM, orbit simulation,
and pointing estimation of each radiometer after launch of the Saab Backward
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ALOS. GCP is necessary to evaluate the geometric accuracy s M NIS
caede
and validate the generated DEM.
Nadir
2. CALIBRATION AND VALIDATION PLAN
2.4 PRISM Characteristics Swath width 70km —
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Figures 1 and 2 illustrate the PRISM observation geometries, "V
and Table 1 summarizes the main characteristics of the PRISM. Sub-satellite track
PRISM is a panchromatic radiometer with a 2.5-meter spatial
: : ; boi Figure 2. Observation geometry of nadir and backward modes
resolution. It consists of three independent optical systems for
