The development of a multispectral scanner data analysis console is reported that incorporates a wideband tape unit, a teletypewriter, a digital computer, and color display as well as numeric display terminals. The device is able to digitize infrared scanner images and displays color differences according to signal differences between analog channels

Arldt, M. J.

Davis, J. E.

Helmke, C. A.

Kell, T. R.

Wilson, E. L.

English

NASA Technical Reports Server

SECTION 24 j7 2 32 ? ? 3 24-1
CONSTRUCTING AND MANIPULATING COLOR
IMAGERY FROM DIGITAL DATA @20@DG 0
by
J. E. Davis, C. A. Helmke, T. R. Kell, M. J. Arldt, E. L. Wilson
Lockheed Electronics Company, Inc.
Houston, Texas
ORIGINAL CONTANS
INTRODUCTION COR L - -
The University Centers of Excellence were the leaders in the dev-
lopment of airborne scanner systems, the related data processing and the
application of this data. When the Earth Observations Division at the
Manned Spacecraft Center decided to use airborne scanners, much of the
technology resulting from the work at these centers was utilized. One
of the more significant areas in thich this technology was advanced by
MSC was in the development of more sophisticated Data Analysis Station
(DAS) Equipment which allows complex manipulation and subsequent ids-
play of the sensor output. A major consideration for the new DAS was
to have an interactive system which would aid investigators, who were
not computer oriented, in examining the data.
EQUIPMENT
The Bendix Corporation developed the 24 band multispectral scanner
system (MSS) and a DAS (Fig. 1) which are now at MSC. A second DAS
(Fig. 2) was developed by Aerojet General primarily for use with the
Passive Microwave Imaging System (PMIS). The manufacturers of these
two DAS supplied both the hardware and the software for these systems.
The following is a listing of the basic units which make up the DAS's.
Some of these units are shared between the two systems.
a. An Ampex FR1900 14-track wide-band tape unit.
b. An ASR-33 teletypewriter.
c. A Systems Engineering Laboratories 810B computer with 16K
word memory, 2 digital tape controller units and 3 separate
digital magnetic tape units.
d. An operator console containing a color display device.
https://ntrs.nasa.gov/search.jsp?R=19720021673 2020-03-23T09:08:07+00:00Z
24-2
e. A multi-bay rack assembly containing a 9 inch strip film
recorder and system control logic.
f. A 1000-line-per-minute line printer.
g. A 600-card-per-minute card reader.
h. An 800 character numeric display terminal which can be used
interactively with the system.
FUNCTIONS OF DAS
Figure 3 shows the MS DAS console and Figure 4 is of the PMIS DAS
console with the interactive display terminal on the right. Figure 5
shows how sensor data is processed in the DAS to cut down on the volume
of data being handled by the large scale computers. Data from these
larger computers comes back to the DAS for display and film recording.
The DAS is used to perform the following functions on scanner data:
1. Editing of flight tapes by transferring to 9 track tape only
that portion of the data to be studied in detail. Training
sample selection is a practical application of editing.
2. Screening flight tapes (or other processed tapes) by creating
black and white or color imagery on the T.V.
3. Producing hard copy in the form of film transparencies in
color or black and white.
4. Outputting data on the line printer.
Item 2 is the principle part of the discussion in this paper.
After the analog PCM tape from the scanner has been read a tape
interface unit converts this to digital data and it is input to the
computer. Figure 6 shows how the computer can then convert the sensor
based data to color signal data using any of a number of algorithms
designed for this purpose. The DAS system then records this processed
data on a disc after going through a buffer unit. The disc then feeds
the T.V. display through the digital to analog converter.
24-3
DATA FORMAT
MS DAS
On the MS DAS the software algorithms must produce color signal data
in the format required by the disk. The format is a 5-bit word which
allows for 32 distinct values (0-31). The relative intensity of a par-
ticular color signal is dictated by the 5-bit color signal word. A word
of all zeros produces no signal for that color while a word of all l's
produces a maximum intensity. Values between 0 and 31 produce a propor-
tional brightness. Thus at each addressable element on the T.V., the
data stored on the disk controls the color presentation by specifying the
intensity of each of the three colors. Since the disk holds one T.V.
frame of data each new scan line that is sent to the disk replaces the
oldest scan line. The vertical synchronization signal is adjusted auto-
matically so that the new data appears at the top of the screen. This
creates a moving scene effect as would be experienced while looking down-
ward through an aircraft window. The rate at which the scene appears to
move past the window is determined by the speed at which the computer
formats new lines and sends them to the disk.
PMIS DAS
The method used by the PMIS DAS is somewhat different but uses the
same principle. A major difference is that while the MS DAS provides for
32 possible intensities for each color the PMIS DAS provides for 16 levels
of green, eight of red and four of blue. This seems to be about as many
levels as the eye can distinguish as shown in Figure 7.
DATA SOURCES
Many data sources suitable for color imagery on the DAS are now
available or in development. The DAS requires that the data be on either
a 14 track PCM tape compatible with the Ampex FR1900 or on a 9-track 800
BPI digital tape. Data recorded on other types of tapes must be con-
verted. Analog tapes for example, must be digitized before coming to the
DAS. To date, color imagery has been generated from the Bendix 24 channel
scanner and from RS14 Infrared Scanner data digitized at MSC. In addition,
aerial photos have been digitized on a microdensitometer and subsequently
displayed.
24-4
COLOR IMAGE CONSTRUCTION
MSDAS
Three specific algorithms are used when processing data with the MS
DAS. All of these algorithms are based on a function which is a linear
combination of the data channels. This function is called linear trans-
formation (LT) and is of the form:
LT = A0 + AC 1 + A2C2 + ..***A24 C24
where A's are coefficients and the C's represent sensor values of the
designated channels.
One algorithm is called Normal Linear Transformation and is simply
three separate linear transformations where the intensity for a CRT gun
(I) is proportional to the linear transformation LT
IR proportional to LT1
IG proportional to LT2
I
B
proportional to LT3
Figure 8 is an example of outputs from this time manipulation.
The red display, is of a thermal IR channel (9.3-9.8 pm) from the 24-
band scanner. The green display, Figure 9, is of a near IR channel
(1.18-1.30 pm) and the blue display, Figure 10, is of the blue channel
(.46-.50 pm). Figure 11 shows the combined display. Figure 12 shows
one channel of data using a linear transformation to get different
intensities of blue. Figure 13 shows this same channel of data after
the table of color codes has been applied to the different signal
levels.
Another algorithm is called Contrast Enhancement. This algorithm
uses only 1 linear transformation. Theresult of the linear transforma-
tion is then used as an index to a table of pre-defined color codes.
I
R
= RED (LT) i.e. the LTth RED value
I = GREEN (LT)
IB = BLUE (LT)
Figure 12 shows one channel of data using a linear transformation
to achieve different intensities of blue. Figure 13 shows this same
channel of data after the table of color codes has been applied to the
different signal levels.
24-5
A third algorithm is called Linear Discriminant. It uses three
linear transformations but the intensities are either zero or the maximum
depending upon whether the result of the transformation meets a given
threshold
IR = 0 if LT1 < THRESH1 i = 31 if LT1 > THRESH1
G = 0 if LT2 < THRESH2 IG = 31 if LT2 > THRESH2
IB = 0 if LT3 < THRESH3 IB = 31 if LT3 >THRESH3
Figures 14 (9.3-9.8 m), 15 (1.18-1.30 m), and 16 (.46-.50 m)
show data which is above the treshold for these three channels.
Figure 17 shows the combined display. White is produced when all 3
channels exceed the treshold. When only the red and green channels
exceed this limit yellow is displayed. Where blue and red exceed the
limit magenta results and when blue and green exceed the limit the
cyan portion of the image (oil tanks) is shown.
PMIS-DAS
The PMIS DAS is used with a program called Color Study which is
similar to Contrast Enhancement. The user can very easily define his own
color tables with the numeric display terminal. The PMIS scanner had not
been flown at the time this paper was written and so none of the data was
available for publication. Data from other sensors has been displayed on
this DAS in the absence of PMIS data.
Figure 18 shows 2 color charts made up on the interactive console
for the Color Study program. The bottom portion shows all 512 possible
colors which may be called upon to generate a color chart.
The data for the image in Figure 19 came from digitizing the two
analog channels of the RS14 infrared scanner (3.0-5.5 pm and 8-14 Wm).
The channels are displayed side by side using the same color chart for
each. Thus the color differences shown represent actual signal differ-
ences between the two channels.
Figure 20 is another example of imagery using the Color Study
program. The data was obtained by digitizing infrared color film
with a microdensitometer and recording on tape.
The imagery in Figure 21 was produced by a simulation study of tem-
peratures in Trinity Bay. Figure 22 represents the same input data
applied to a different color chart.
24-6
SUMMARY
The comparison of Figures 21 and 22 adequately demonstrate how much
easier it is to distinguish different colors than it is to distinguish
shades of grey or in this case shades of green.
All of these examples show what a capable and flexible tool for
principle investigators the DAS is and how it can be applied to a large
variety of sensors.
Future plans call for processing data from sensors such as the PMIS,
the Scanning Imaging Spectroradiometer (SIS), the Skylab S-192 multi-
spectral scanner, and the ERTS systems.
FIGURE LEGENDS
Page
1. Multispectral Scanner Data Analysis Station (MS DAS) 24-8
2. Passive Microwave Imaging System Data Analysis Station 24-9
(PMIS DAS)
3. MS DAS Interactive Console 24-10PMIS DAS Interactive Console
4. PMIS DAS Interactive Console 24-11
5. Sensor Data Flow 24-12
6. DAS Data Flow 24-13
7. The Intensities of the Three Primary Colors
4 Blue, 8 Red, and 16 Green 24-14
8. Thermal IR Channel (9.3 - 9.8pm) Data From the 24 Channel
Scanner on the Red CRT Gun 24-15
9. Near IR Channel (1.18 - 1.30pm) Data from the 24 Channel
Scanner on the Green CRT Gun 24-16
10. Blue Channel (.46 - .50pm) Data from the 24 Channel Scanner
on the Blue CRT Gun 24-17
11. Data from Figure 8, 9, and 10 Displayed Simultaneously 24-18
12. Linear Transformation Applied to Data in Monochrome 24-19
13. Same Data as in Figure 12 with Color Table Applied 24-20
14. Linear Discriminate Algorithm Applied to Thermal IR Channel 24-21
15. Linear Discriminate Algorithm Applied to Near IR Channel 24-22
16. Linear Discriminate Algorithm Applied to Blue Channel 24-23
17. Combined Display of Data Used for Figures 14, 15, and 16 24-24
18. Color Charts Displayed on the PMIS DAS 24-25
19. Display Constructed from Digitized IR Scanner Data using
Color Study 24-26
20. Imagery Constructed from Digitized Photographic Data 24-27
21. Display of Math Model of Temperatures in Bay 24-28
22. Same Data as in Figure 21 with a Different Color Chart
Applied 24-29
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Constructing and manipulating color imagery from digital data

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