An attempt is made to draw a parallel between the existing geophysical data processing service industries and the emerging earth resources data support requirements. The relationship of seismic data analysis to ERTS data analysis is natural because in either case data is digitally recorded in the same format, resulting from remotely sensed energy which has been reflected, attenuated, shifted and degraded on its path from the source to the receiver. In the seismic case the energy is acoustic, ranging in frequencies from 10 to 75 cps, for which the lithosphere appears semi-transparent. In earth survey remote sensing through the atmosphere, visible and infrared frequency bands are being used. Yet the hardware and software required to process the magnetically recorded data from the two realms of inquiry are identical and similar, respectively. The resulting data products are similar

Jennings, J. D.

Sabels, B. E.

English

NASA Technical Reports Server

Paper I 13 
DIGITAL INTERACTIVE IMAGE ANALYSIS BY ARRAY PROCESSING 
Bruno E. Sabels, Tetra Tech., Inc., Houston, Jerry D. Jennings, Geocom, Inc., Houston 
Geophysical and ERTS Data Processing Are Similar 
This paper endeavors to draw a parallel between the existing geophysical 
data processing service industries and the emerging earth resources 
data support requirements. 
ERTS data analysis i s  natural because in either case data is  digitally 
recorded in the same format, resulting from remotely sensed energy 
which has been reflected, attenuated, shifted and degraded on its path 
from the source to the receiver. 
acoustic, ranging in frequencies from 10 to 75 cps, for which the litho- 
sphere appears semi -transparent. 
through the atmosphere, visible and infrared frequency bands a re  being 
used. 
ically recorded data from the two realms of inquiry a r e  identical and 
similar, respectively. The resulting data products a re  similar. 
In several decades of evolution, the geophysical data processing industry 
has become application oriented and cost effective. 
very intensive competigon. 
survey data analysis, which has hardly entered the commercial sector. 
Therefore, i t  is interesting and probably beneficial to consider the 
The relationship of .seismic data analysis to 
In the seismic case the energy is 
In earth survey remote sensing 
Yet the hardware and software required to process the magnet- 
* 
It is driven by a 
This is not the case at this time in earth 
potential of an existing technology with regard to a developing one. 
Detailed Comparison Between ERTS and Geophysical Data 
A survey of ERTS-1 investigations discloses several categories of 
efforts which can be compared with seismic data processing categories. 
F i r s t  there a r e  the optical and digital filtering and enhancement techniques, 
1199 
https://ntrs.nasa.gov/search.jsp?R=19730019602 2020-03-17T08:46:59+00:00Z
which attempt to eliminate noise or improve contrast in the resulting 
display. With improved processing algorithms, these lead to classi- 
fication techniques, and to hybrid selection and suppression methods. 
Then there a re  highly sophisticated spectral and spatial detection efforts, 
aimed at low signal-to-noise contrasts, for the detection of subtle shades 
of grey or  the respective color, which represent differences in soils, 
chlorophyll, stress,  infestation, or other manifestations of resources 
conditions. Because the dynamic range of the information which can be 
derived from any one recorded element is limited by the number of bits 
per byte, several spectral o r  temporal exposures a re  generally stacked 
and correlated. 
Conversely, seismic processing starts with corrective programs, followed 
by correlative displays of features of similar reflective, attenuative and 
conductive properties, which in geological terms are  better known as  
s tratigraphy and structure. 
the industry has learned to isolate and enhance, even in color, any 
combination of variables of value to the explorationist, ranging from 
velocities, energies, frequency shifts, and reflection coefficients to rock 
type, porosity, water content, temperature, pressure, and hydrocarbon 
concentration. The more sophisticated analyses a r e  based on relatively 
large arrays of data which have been precisely recorded, in as many as  
48 channels, under rigid gain control. The reconstruction of the signal 
characteristics in the computer is possible within a large dynamic range, 
exceeding 100 db and approaching 180 db. This precision is  not available 
for ERTS data, where acquisition and transmission limitations, and 
restrictions of spectral and temporal multiplicity leave room for improve - 
ment in later, more advanced eras  of earth survey. 
A detailed discussion of a specific enhancement of hydrocarbon content 
in gas and oil bearing sediments was recently published by C. I. Craft 
(Oil and Gas Journal, Feb, 19, 1973, pp. 122-125). 
for the display of geophysical parameters have been publicized by several 
geophysical data processing companies, both in the U, S. and abroad. 
Over and beyond these fundamental displays, 
Color processes 
Interactive Mode and Different Service Concepts 
Geophysical data services do not limit their attention and competition 
to a more accurate and useful information content of the final product. 
They have also devised new ways of meeting and involving the client, 
and of participating in designing the product of his choice, where and 
when he needs it. This service approach i s  today completely outside 
of the realm of ERTS investigations, where time and costs are still 
relatively secondary considerations. In geophysical processing, the 
usual interactive involvement of the geophysicist in the man-machine 
cycle has been expanded to include the client, who is generally the 
user of the data. 
or thousands of miles away from the computer facility--allow real time 
display of intermediate data processing steps, and allow decisions and 
participation as to further iterations, choices or measures of enhance- 
ment. There a r e  two more dimensions of service, however, which a re  
available to the geophysical data user. Some service companies have 
adapted and standardized their data processing capability s o  that they 
can take advantage of existing computer centers around the world. 
may, for example, use the “brand Xi’  computer system, and they can 
make i t  work wherever a business potential and a computer location 
coincide, be it Chicago, Calgary, London or  Singapore! And in even closer 
interaction with the field crews, some geophysical service companies a r e  
dispatching miniaturized computer centers into the field, wherever i t  
may be, to work literally tied in with the field data acquisition. 
Remote terminals in major user’s offices--hundreds 
They 
Service at Low Costs - A Goal for ERTS Users 
Some day, similar customer services will exist in earth survey data 
anlaysis as  a re  described above. Indeed, the multi-user possibilities 
of ERTS data promise even cost savings over the generally specialized 
geophysical data utilization. 
2 $0. 02 per km 
frames. 
equipment which is attached to the computer for the more efficient 
handling of large amounts of data. For the geophysical data industry, 
such equipment and the corresponding soft ware were developed by the 
Shell Oil Company. 
A data center has quoted rates as low as  
for image data correlation, based on two compatible 
This low unit cost results from the use of special purpose 
1201 
Other Applications in NASA Earth Observation Programs 
So far, only ERTS data were addressed. 
physical data technology is in the Skylab/EREP program. 
particularly appropriate because the data recorded in manned missions 
need not be restricted as  much as ERTS data, as far as  data intensity 
is concerned. From such applications of geophysical methods, changes 
may result in the design or performance characteristics of later 
generation earth survey data acquisition systems. 
Mutual Technology Trans fer 
The parallel between geophysical and earth survey data analysis is  
hampered at this point by insufficient "channels" of ERTS data available 
to us. 
in the same format as  ERTS CCT's. 
ERTS data in government and industrial processing facilities. And we 
expect that this work will benefit the geophysical data industry as  well, 
as evidenced by the introduction of false color processes in seismic 
data displays. 
One other application of geo- 
This is 
Therefore, most of our efforts were based on geophysical data, 
We can interchange seismic and 
Potential of High-speed Processes for ERTS Data 
In summary, the array processor I s  introduced as an instrument to 
free the investigator from data processing chores, so that he can use 
his time more efficiently for the interpretation and utilization of the 
data. 
not investigators. 
data processing industry, will therefore increase the potential for the 
application and utilization of ERTS data. 
discussed data industries a r e  being pursued. 
Conversely, data products a re  made available to users who a r e  
The service, patterned after the commercial seismic 
Further details of the two 
Appendix - Array Processor Capabilities 
This section describes the array processor, developed by Shell Oil 
Company, which is used in conjunction with a medium to large computer 
center. There a re  several brands of processors and computer systems 
on the market, which may have similar capabilities. 
The AP,  as the array processor is called for short, performs specific 
instructions in memory independent of the central processing unit o r  
CPU. This makes the AP similar to a multi-processing system, except 
1202 
that the A P  has a hard-wired instruction set of about 21 operations 
which a r e  most common in geophysical data processing. 
operations need not be detailed in the programming software, step 
by step, but a r e  executed instantaneously by one command. 
Initially, the AP was used for multiply/add operations which i t  performs 
effectively in 250 nanoseconds. 
were done in the hardware algorithm modules. Today, many other 
mathematical functions have been utilized or adapted, and the AP is 
typically employed for about 7070 of the geophysical calculations. 
instructions available include the following: 
These 
About 2570 of all geophysical calculations 
The 
vector inner product partial matrix multiply 
s u m  of squares sum of vector elements 
scalar multiplication vector element by element multiply 
scalar add vector element by element sum 
complex vector element multiply fast Fourier transform 
convolving multiply limits readout 
interpolations. 
Many of these instructions a re  common to image correlation, enchance- 
ment and analysis. 
The single most effective instruction i s  the convolving multiply. 
improvement realized by using the A P  versus the CPU is better than 
20 to 1. 
-convolution, cross -correlation, and auto-statics. These geophysically 
oriented processes a r e  mathematically applicable in image correlation, 
correction and classification. 
The 
The instruction i s  used in filtering, auto-correlation and 
The interpolation instruction i s  another heavily engaged AP favorite. 
Improvements in processing time a r e  better than 9 to 1 over the CPU. 
This instruction is used in fiducial and statics correction, stacking and 
resampling of data. Functionally, these processes correspond to the 
stretching or compressing of data, either linearly or in time. In image 
analysis of ERTS data, similar instructions become important in dealing 
with registration and boundary problems. 
The partial matrix multiply instruction yields improvements of 4 to 1 
and is used in calculating the Z transform filters by polynomial 
division, recursive filtering, velocity determination, and for preparatory 
sine and cosine function generation for the fast Fourier transform 
algorithm. 
The fast Fourier transform is widely used to convert between the time 
and frequency domains, so as to expedite the processing. 
better than 5 a r e  realized in using the A P  versus the CPU. 
Savings of 
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Digital interactive image analysis by array processing

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