INTRODUCTION 
Remote sensing satellites for earth observations and 
meteorological applications have opened up new avenues for 
exploration of resources and predicting atmospheric behaviours 
and thus have established a system for obtaining useful information 
, about the earth's surface and its surroundings. Image processing 
has therefore become an important aspect of the remote sensing 
programme for fruitful exploitation of information collected 
through the remote sensing sensors. 
Today, an enormous volume of data is gathered, which 
contains a great deal of information in pictorial form. For 
effective utilization, timely dissemination of data and its processing 
to extract useful information to arrive at a decision quickly | 
requires a new breed of image processing tools. VIDEO-RATE 
is useful concept for real time image processing applications 
which can help in meeting these objectives significantly. 
The intent of this paper is to discuss several aspects of the 
VIDEO-RATE image processing technology and developments at 
the Space Applications Centre, Indian Space Research Organisation 
(ISRO). 
VIDEO-RATE IMAGE PROCESSING - AN OVERVIEW 
VIDEO-RATE image processing means processing at 
television rate, i.e. one frame of picture is processed in 1/25th 
of a second (TV refresh rate). Thus, an electronic image frame of 
S2w512pixels can be processed in just 40 milli seconds, i.e. 
6. 5 million bytes per second. 
Quick look display technique using analog tube memoey has 
been extensively used for remote Sensing and industrial applications, 
However, this has several limitations such as resolution, shading , 
geometric distortions and signal non-linearities. Development in 
digital devices of 4K and 16K static and dynamic RAM made it 
possible to build frame memories of 512 x 512 x 8 bits. 
A digital video-rate image processing system is developed 
using digital video frame memory as the main building block. 
These memory building blocks associated with ultra high speed 
computational logic and processing hardware allow a number 
of functions to be carried out in real time. Video techniques are 
used to convert data into television compatible format which can be 
viewed either on a monochrome or colour TV display for real time 
applications. Use of feedback allows man-machine interactions in 
realtime. Processed data can be recorded both in CCT format or 
video format for post viewing and analysis. 
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