COMPUTER, OPERATING SYSTEM AND 
DISPLAY INDEPENDENT IMAGE ANALYSIS 
W. MURRAY STROME 
PCI 
4800 Dufferin Street, Suite 202 
DOWNSVIEW, Ontario, Canada 
M3H 5S8 
INTRODUCTION 
Before the advent of NASA's LANDSAT program, the only multispectral remote 
sensing data available to the scientific community was that obtained from 
airborne scanners or aerial photography. The radiometric and geometric 
errors in this data were so great that the bulk of the research effort had to 
be directed toward error correction. With LANDSAT, for the first time, large 
amounts of data became widely available. Moreover, the data were of 
sufficiently high quality that research could concentrate on the analysis of 
the data, rather than its correction. 
Soon, digital image analysis systems began to be offered as commercial 
products. Software was available (e.g., VICAR and LARSYS) to U.S. 
organizations for operation on mainframe computers. 
Most commercial image analysis systems were based on specific hardware 
configurations. The DEC PDP-11 family of computers was the most popular 
choice, with interactive displays either manufactured by the company 
providing the system, or selected from a choice of generic devices offered by 
several manufacturers. 
With the advent of the new VAX series of computers from DEC, many companies 
offering image analysis systems were faced with a need to convert their 
software from the PDP-11 and the RSX-11 operating system to the VAX and VMS. 
Many manufacturers went through the laborious task of converting their 
software directly from the PDP-11 to the VAX using "brute force" techniques: 
code was transferred to the VAX, recompiled and "debugged" by searching out 
those sections which were computer or operating system dependent, and was 
then manually changed. 
PCI chose a different route for this conversion process. Having already had 
the experience of converting software from a PDP-11 to a Perkin-Elmer 
computer, we decided that a better way to perform such conversions had to be 
found. The result was the development of EASI/IMP, a tool which can be used 
to develop software that is relatively machine independent. 
HISTORY OF SOFTWARE ARCHITECTURE 
Morland (1985) has given a comprehensive description of the evolution of 
software architecture, with some predictions as to the direction such 
development may take in the future. 
Stage I: 1945-1965 
The earliest computers were programmed by the electrical engineers and 
mathematicians who designed them. They were programmed in machine language 
using octal or hexadecimal codes to represent the actual binary numbers 
stored in the computer to control its actions and those of its peripherals. 
Typically, the programmer booked a block of time on the computer and entered 
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