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Proceedings of the Symposium on Progress in Data Processing and Analysis

Manfred Ehlers
National Center for Geographic Information and Analysis (NCGIA)
Department of Surveying Engineering
University of Maine
Orono, ME 04469
E-Mail: ehlers@mecanl.bitnet
Interactive image processing systems for the analysis of remotely sensed data are readily
available for IBM compatible PCs and various mini- and micro-computers. Image
processing software to be used on Macintosh PCs, however, has usually been
associated with desktop publishing or medical/biological applications. With the advent
of standard color displays for the Macintosh II series, image processing systems could
be expanded to include remote sensing applications. Combining the user-friendly
Macintosh interface with the capability of displaying multispectral remote sensing image
data offers the unique possibility of a 4th generation image processing system design.
During a one-semester course in image processing, students of the Department of
Surveying Engineering at the University of Maine designed and implemented the Dirigo
software package for the analysis of remotely sensed data on an off-the-shelf Macintosh
II. The students were assigned to teams, each tackling a specific component of the
system. Coordination was maintained through status reports and intensive discussions
and resulted in the integration of all application software components in one common
user interface.
Concentrating on the components necessary for remote sensing applications, Dirigo
contains menus for (a) point operations; (b) spatial filtering; (c) geometric corrections
and georeferencing; (d) multispectral classifications; and (e) general utilities (e.g. pan
and zoom). The software was written from scratch using exclusively Macintosh intuitive
tools for the interface design. This allows inexperienced users and computer novices to
get familiar with the system quickly and avoids unnecessary overhead in the learning
This paper describes specifications and performance of the Dirigo system, compares it
with existing software packages and outlines future developments.
The past decade has witnessed rapid technological development in computing hardware
producing continual reductions in the cost of systems. High level microprocessors in
personal computers vastly outperform their forerunners of only a few years ago and
challenge minicomputers in performance. Two manufacturers of high performance
chips for the use in super microcomputers have established themselves as marketleaders,
Intel and Motorola (Ferns and Press, 1988). The Intel 8()xxx series and the Motorola
68xxx family are the most widely used and may be associated with the 'IBM world'