AUTONOMOUS AND CONTINUOUS GEORECTIFICATION OF MULTI-ANGLE IMAGING SPECTRO-RADIOMETER 
(MISR) IMAGERY 
Veljko M. Jovanovic, Michael M. Smyth, and Jia Zong 
Jet Propulsion Laboratory 
Mail Stop 169-314 
4800 Oak Grove Drive 
Pasadena, CA 91109 USA 
KEY WORDS: Navigation, Rectification, Registration, Geometric, On-line Satellite Mapping 
ABSTRACT: 
A theoretical concept underlying the design of the science data processing system responsible for the autonomous and con- 
tinuous georectification of multi-angle imagery is the subject of this paper. The algorithm is focused on a first time attempt to 
rectify and map project remotely sensed data on-line, as it comes from the instrument. The algorithm deals with the following 
issues: a) removal of the errors introduced by inaccurate navigation and attitude data, b) removal of the distortions introduced 
by surface topography, c) achieving a balance between limited hardware resources, huge data volume and processing 
requirements, autonomous and non-stop aspects of the production system. The key elements of the algorithm are: a) photo- 
grammetric image point intersection, b) image matching, c) adaptive image-to-image transformation and d) ancillary (input) 
dataset. 
1. INTRODUCTION 
The Multi-Angle Imaging Spectro-Radiometer (MISR) is part 
of an Earth Observing System (EOS) payload to be 
launched in 1998 (Diner, 1991). The purpose of MISR is to 
study the ecology and climate of the Earth through the 
acquisition of systematic, global multi-angle imagery in 
reflected sunlight. In order to derive geophysical parameters 
such as aerosol optical depth, bidirectional reflectance fac- 
tor, and hemispheric reflectance, measured incident radi- 
ances from the multi-camera instrument must be 
coregistered. Furthermore, the coregistered image data 
must be geolocated in order to meet experiment objectives 
such as: a) produce a data set of value to long-term monitor- 
ing programs and allow intercomparassions of data on time 
scales exceeding that of an individual satellite, and b) pro- 
vide Earth Observing System (EOS) synergism, and allow 
data exchange between EOS-platform instruments. 
In order to provide coregistered and geolocated data, the 
ground data processing system is designed to geometrically 
process multi-angle multispectral data, so that they all con- 
form to a common map projection. This is the first time 
attempt to rectify and map project remotely sensed data on- 
line, as it comes from the instrument. We define this seg- 
ment of continuous and autonomous ground processing as 
“georectification”, and the derived product as the Georecti- 
fied Radiance Product. There are two basic parameters of 
the Georectified Radiance Product depending on the defini- 
tion of the reflecting surface: a) ellipsoid-projected radiance, 
and b) terrain-projected radiance. The ellipsoid-projected 
radiance is referenced to the surface of the WGS84 ellipsoid 
(no terrain elevation included) and the terrain-projected radi- 
ance is referenced to the same datum including a DEM over 
land and inland water. 
This paper describes the theoretical concepts underlying the 
176 
algorithm responsible for the georectification and production 
of the terrain-projected radiance product. This processing 
segment must remove the distortion introduced by the 
topography that occurs when imaging with multiple viewing 
angles. In addition, this is the only processing step which will 
directly deal with the errors in the supplied spacecraft 
ephemeris and attitude data. In particular, we describe the 
geometry of the MISR imaging event and the characteristics 
of the terrain-projected radiance product. Then we present a 
description of the algorithm used and discuss the simulated 
input data and prototype test results. 
2. GEOMETRY OF THE MISR IMAGING EVENT 
In 1998, MISR will be launched aboard the EOS AM-1 
spacecraft. The baseline orbit has been selected by the 
EOS project to be sun-synchronous, with an inclination of 
98.186? . The orbit period of 98.88 min. and orbit precession 
rate of 0.986? /day imply a ground repeat cycle of the space- 
craft nadir point of 16 days. This orbit is referred to as the 
“705 km” orbit, although the actual altitude varies from about 
704 km to a maximum of 730 km. The orbit will have an 
equatorial crossing time of 10:30 a.m. 
The MISR instrument consists of nine push-broom cameras. 
The cameras are arranged with one camera pointing toward 
the nadir (designated An), one bank of four cameras point- 
ing in the forward direction (designated Af, Bf, Cf, and Df in 
order of increasing off-nadir angle), and one bank of four 
cameras pointing in the aftward direction (using the same 
convention but designated Aa, Ba, Ca, and Da). Images are 
acquired with nominal view angles, relative to the surface 
reference ellipsoid, of 0°, £26.1°, +45.6°, +60.0°, and £70.5° 
for An, Af/Aa, Bf/Ba, Cf/Ca, and Df/Da, respectively. The 
instantaneous displacement in the along-track direction 
between the Df and Da views is about 2800 km (see Figure 
1). Each camera uses four Charge-Coupled Device (CCD) 
International Archives of Photogrammetry and Remote Sensing. Vol. XXXI, Part B2. Vienna 1996 
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