791 
PRECISE GEOMETRIC PROCESSING 
OF STEREO MEIS IMAGERY 
J.R. Gibson 
Canada Centre for Remote Sensing 
M. Buchheit 1 
Prologic Systems Limited 
Abstract 
This paper discusses the considerations involved in preparing and processing electro-optical stereo imagery from an 
airborne Multi-detector Electro-optical Imaging Scanner known as MEIS for input into Geographic Information Sys 
tems for Remote Sensing analysis or other interpretative applications. MEIS was built by Macdonald, Dettwiler and 
Associates for the Canada Centre for Remote Sensing (CCRS) and has been evaluated extensively over the past several 
years. The MEIS was subsequently modified by CCRS to have a stereo imagery acquisition mode by adding external 
mirrors to create both a forward-looking and an aft-looking channel. These two channels operate simultaneously to 
provide single-pass stereo coverage. Due to the limited swath width of the present MEIS instrument, it is frequently 
necessary to fly several parallel flight lines in order to obtain coverage of a desired test area. This paper outlines 
the procedures that are followed in building up a composite imagery mosaic of the coverage area based on several 
individual flight lines. The adjustment of the imagery to ground control points is based on rigorous photogrammetric 
techniques involving the Collinearity and Coplanarity Conditions for the MEIS imager and implicit use of data from 
the associated inertial navigation system. The adjustment allows for the simultaneous solution of multiple input flight 
lines and is able to accommodate both fore/aft and side to side stereo imagery. The system computes a low order 
polynomial estimator to model the errors of the inertial navigation system data and then adjusts the position and 
attitude data after the best fit to the control points has been achieved. The corrected position data may then be 
used in the subsequent geometric processing of the imagery. Some of these processing stages include: The removal 
of terrain height distortions necessary for the generation of ortho-imagery; a simple radiometric balancing necessary 
before an imagery mosaic may be made and in the future; generation of terrain height data from the forward and aft 
looking channels. The paper summarizes the results of several accuracy evaluations of the fit of imagery to ground 
control points. There is also a sample of an ortho-imagery mosaic to illustrate the effects of the correction processing. 
Key Words: electro-optical, stereo, imagery, MEIS, geometric correction, photogrammetric, mosaic 
1 Introduction 
The purpose of this paper is to describe the current state 
of the geometric correction and resampling software at 
the Canada Centre for Remote Sensing (CCRS) for the 
digital imagery obtained from the Multi-detector Electro- 
optical Imaging Scanner (MEIS). The acceptance of air 
borne scanners has been slow over the years principally 
because of poor spatial resolution and distortions induced 
by aircraft motion. However with the developments th«Vt 
'Under contract to CCRS 
have taken place in imaging technology, where both the 
spatial and radiometric resolutions have improved dra 
matically, and at CCRS in the measurement of aircraft 
motion and in the development of data processing al 
gorithms for post-flight correction of the imagery, these 
problems are close to being solved. In particular, a new 
prototype imager has been built at CCRS with 6000 pix 
els, 12 bits of radiometric resolution and a field of view 
of 70 degrees (Neville, 1989). 
During this same time, changes have been occurring in