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Remote sensing for resources development and environmental management
Damen, M. C. J.

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Symposium on Remote Sensing for Resources Development and Environmental Management / Enschede / August 1986
Digital elevation modeling with stereo SIR-B image data
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Canada Centre for Remote Sensing, Ottawa
F.Plourde & T.Toutin
DIGIM, Montréal Canada
ABSTRACT: A stereo SIR-B image data set has been used to produce a digital elevation model (DEM) for a test
site located in the Mount Shasta area in California. The stereo pair was formed with images acquired at 53
and 29 degree incidence angles, both on the same side. A digital method has been developed for the extraction
of differential parallaxes which relies mainly on a hierarchical nested zoomed correlation procedure. The
efficiency of the proposed method for automatic production of DEM is investigated in relation to terrain and
SAR parameters.
The possibility of deriving elevation data from
stereoscopic radar images has been investigated in
the past mainly in relation to geometry
information necessary for adequate terrain
modeling (Leberl et al, 1985; Derenyi and Stuart,
1984) . It has been shown that radargrammetry
offers possibilities for accurate terrain mapping
under certain conditions, but it is generally more
difficult to achieve, compared to traditional
photogrammetry, due primarly to the inherent
geometric and radiometric characteristics of radar
images especially those derived from aircraft
systems. To date the question has been addressed
using analog or hybrid analog/digital plotter
equipment requiring film products and operator
visual interaction.
The second Shuttle Imaging Radar (SIR-B)
experiment offered for the first time the
possibility to investigate the use of digital
techniques for terrain modeling with spaceborne
multi-incidence angle and digital L-band
(synthetic aperture radar) SAR images (the SIR-B
Science...,1984). The present research paper
concerns results on the evaluation of a method
developed at the Canada Centre for Remote Sensing
for production of digital elevation models from
SIR-B data. The method had been primarily
developed for processing visible/infrared (VIS/IR)
imagery such as that from LANDSAT or SPOT
satellites (Simard and Krishna, 1983; Simard,
1982) but has been refined in order to effectively
account for geometic and radiometric differences
between VIS/IR and SAR images. A test site was
selected in the rugged topographic area of Mt.
Shasta in California (lat/long » 41° 53'N/122°
52'W) where elevations range approximately from
500 to 2200 metres above sea level. The Mt.
Shasta site is also very well known from the
production of a SIR-B perspective view movie
presented at the JPL SIR-B Workshop (Kobrlck,
1985) .
SIR-B image data acquired in October 1984 at the
two incidence angles of 29 and 53 degrees were
investigated for automatic DEM production.
Basically, the overall process was divided into
four main steps: geometric and radiometric
preprocessing, automatic stereo image matching,
three-dimensional modeling (ray intersection) and
orthographic DEM/SIR-B image production. Precise
image correction and geometric modeling have been
made possible by using few ground control points,
(GCPs) digitized from 1:62500 scale topographical
maps, together with post flight ephemeris data
(OPS onorbit postflight...,1983) sampled every 10
The SIR-B image data were digitally processed at
JPL (Curlander, 1984; the SIR-B science...,1984)
with a four look 12.5 metre pixel size (in ground
range representation). However in order to smooth
the image statistics, the input images were
averaged to square 25 metre pixels using a 2 x 2
adjacent cell.
The geometric rectification of raw imagery has
been done by using external parameters including
GCPs and shuttle orbital parameters defined by
position and velocity vectors. The rectification
procedure consisted of moulding the imagery to a
quasi-cartographic projection leaving uncorrected
the parallax effect only. By this mean, both 29
and 53 degree incidence angle images were
\ I
Figure 1. SIR-B range viewing geometry.