Submarine Medical Research

NSMRL Report 1163

Laboratory

13 December 1990

THE EFFECTIVENESS OF A COLOR/SATURATION BEACON AS A NAVIGATIONAL

RANGE INDICATOR

Kevin Laxar

and

S. M. Luria

Released by:

W. G. Walter, CAPT, DC, USN'

Commanding Officer

Naval Submarine Medical Research Laboratory

Approved for public release; distribution unlimited

Naval
THE EFFECTIVENESS OF A COLOR/SATURATION

BEACON AS A NAVIGATIONAL RANGE INDICATOR

Kevin Laxar

and

S. M. Luria

NAVAL SUBMARINE MEDICAL RESEARCH LABORATORY

REPORT NO. 1163

Naval Medical Research and Development Command

and

U.S. Coast Guard Research and Development Center

Contract No. MIPR Z51100-9-0002

APPROVED AND RELEASED BY:

R. G. WALTER, CAPT, DC, USN

Commanding Officer

Naval Submarine Medical Research Laboratory

Approved for public release; distribution unlimited

SUMMARY PAGE

THE PROBLEM

To determine the navigational performance of observers using a simulated aid

to navigation proposed by the U.S. Coast Guard. The aid is a single-station

range beacon that would indicate lateral position in a channel by displaying a

change in color as the vessel operator moved across the channel. The beacon

would show a strong green at one side, gradually changing to white in the center, and increasing to a strong red at the other side.

FINDINGS

The ability of observers to detect deviation from range axis and motion across

range axis was determined for the simulated color beacon both with and

without a white reference light. The sensitivity afforded by this type of indicator to judge on-axis position was found to be questionable, but sensitivity

to motion across range axis was found to be superior to that of alternative

beacons studied previously.

APPLICATION

The findings describe the navigational sensitivity afforded by a color-encoded

single-station range indicator. They will allow comparison with other

proposed single-station range indicators and with current two-station parallax range indicators.

ADMINISTRATIVE INFORMATION

This study was conducted at the Naval Submarine Medical Research

Laboratory under a modification to Contract No. MIPR-Z51100-9-0002 with

the U.S. Coast Guard Research and Development Center, Groton, CT. The

manuscript was submitted for review on 19 October 1990, approved for publication on 13 December 1990, and has been designated as NSMRL Report No.

1163.

iii
ABSTRACT

We evaluated the effectiveness as an aid to navigation of a single-station beacon

which was white when viewed from the centerline of a channel and became increasingly red or green when viewed from off center to the right and left. First we

measured the observers' ability to determine whether a light was white, reddish, or

greenish. A wide range of colors, from 575 nm to 585 nm, were judged to be white,

making it difficult to specify a beacon that would adequately signal center of channel. Second, we measured the ability of the observers to detect a change in color for

slowly changing stimuli. There were seven just noticeable differences in the range of

color investigated. This would provide a sensitivity of 21.8 m (71.4 ft) over a 152 m

(500 ft) wide channel. Measurements were taken with and without a "white" reference light. Under no condition did the reference light improve performance. For

changing stimuli, however, those that were brighter or larger provided better sensitivity than those that were smaller or dimmer.

iv
The Effectiveness of a Color/Saturation Beacon as a Navigation Range Indicator

The U.S. Coast Guard is evaluating

various methods for indicating to a

navigator if his/her ship is proceeding

properly along a channel or "range." A

general question is whether or not the

two-station or parallax range indicator

can be replaced by a single-station

device. Previous publications have assessed navigators' performance using

several types of parallax ranges (Laxar

and Mandler, 1989), as well as a rotating beam (Luria, 1990) and a flashing

light (Laxar and Luria, 1990) type of

single-station range indicator.

The present study examines the effectiveness of a single-station beacon that

would display a beam of light that

varied in color according to lateral position in the channel, as shown in Figure

1. At the left edge of the channel, the observer would see a saturated1 green

light. Approaching the range axis, the

green light would gradually desaturate

until a white light was seen on the

centerline. With further movement

toward the right edge of the channel, the

light would gradually become pink,

then a highly saturated red. Comparison of the variable light with an adjacent standard white light could provide

a reference for judging the saturation of

the variable light and thus the ship's

position relative to the range axis. This

range display would be similar to a sector light in providing a chromatic code.

A sector light, however provides crude

information about lateral position in the

channel. The proposed light was studied

to determine if a continuously varying

GREEN RED

z

Iz

Lul

CHANNEL POSITION

GREEN ---- WHITE -0 RED

Fig. 1. Chromatic range. When on the centerline a

steady white light is seen. As one moves to the

right, the light changes gradually to pink and then

to deep red. Similarly, movement toward the left of

the channel centerline results in a change toward

green.

1 Saturation refers to the purity of a color stimulus, that is, its richness or the

degree to which it differs from white. Two other aspects of a color stimulus are

hue and brightness.

1
chromatic signal would improve lateral

sensitivity. The results may also apply

to the design of a graded sector beacon,

as well as to a continuously varying

beacon, by specifying the optimal number of step gradations displayed across

the channel.

Studies of saturation discrimination

have found that there are about 20 discriminable steps in color purity between

white and red, and between white and

green (Jones & Lowry, 1926; Martin,

Warburton, & Morgan, 1933), considerably more than, for example, between

white and yellow. Other studies, such

as those of Priest and Brickwedde (1938)

and Jameson and Hurvich (1955),

measured the minimal amount of

spectral light added to white that is just

detectable. These studies all concluded

that saturation discrimination is relatively good in the red and green areas of

the spectrum and poor in the yellow. All

of the studies of saturation discrimination, however, have tested the ability to

perceive differences between two static,

unchanging colors. None has investigated observers' sensitivity to a gradual

change in a light's saturation. In previous reports, however, we have shown

that it can be far more difficult to detect

a gradual change in a moving stimulus

(Laxar & Mandler, 1989) or a flickering

stimulus (Laxar & Luria, 1990) than to

perceive that two unchanging stimuli

are different. We therefore conducted

two experiments. In the first, we

measured observers' ability to discriminate small differences in color from

a white stimulus, in order to assess sensitivity to position on or off the range

centerline (static thresholds). In the

second, we measured observers' ability

to judge gradual changes in color, in

order to assess sensitivity to motion

across the range (dynamic thresholds).

METHOD

Observers

Eight volunteers, ranging in age from

20 to 50 years, participated in both the

static and dynamic experiments. All

had normal color vision and 20/25 or better visual acuity, with their spectacle

correction if required. Four of them

were experienced psychophysical observers.

Apparatus

The stimuli were produced by a twochannel optical system, one channel

providing the variable red-to-white-togreen stimulus, the other providing the

fixed white reference light (Figure 2).

In the variable channel, light from a

tungsten source was passed through a

blocking filter, a polarizing filter, and a

polarizing dichroic filter. As the

dichroic filter was rotated 900 in its

plane, the colors it transmitted gradually changed from red to white and then to

green, as given in Table 1 and shown in

Figure 3. The white reference light was

produced by setting a dichroic filter to

the mean not-red, not-green point of 12

observers. This value was determined

psychophysically prior to the start of the

experiment. The reference light's color

temperature was 3338°K. The stimuli

were calibrated with a PR-703A/PC

Spot SpectraScan fast spectral scanner

(Photo Research Div., Kollmorgen

Corp.).

Light from the two channels passed

through a vertical pair of apertures

separated by a visual angle of 8.2 arc

min on center at the 6 m viewing distance. The reference light, when used,

2
LS

ND O

P •

SH I__

I M

MI

6M 0

Ssc 0

0 OBS

Fig. 2. Diagram of the chromatic range apparatus.

The light from each tungsten bulb (LS) goes

through a collimating lens (L), ground glass (G), a

neutral density filter (ND) when required, a

blocking filter (B), a polarizing filter (P), and a

dichroic polarizer (D or VD). The variable stimulus

goes through and shutter (SH). The fixed reference

stimulus is reflected by a mirror (M). Both light

beams pass through their respective apertures in a

screen (SC) 6 m from the observer. The apertures

are vertically aligned, with the variable stimulus

under the reference stimulus.

illuminated the upper aperture. Two

aperture sizes, subtending 1.0 and 3.5

arc min., were tested. Two luminance

levels, given in Table 1, were tested as

well. The lower luminance was

achieved by placing a 1.0 neutral density filter in each channel.

PROCEDURE

The observer sat with his/her chin in

a chinrest, in a room with barely enough

light to see the large objects in the room.

After a brief practice session, the static

thresholds were always measured first,

with the dynamic thresholds measured

in subsequent sessions. Data were collected and analyzed in terms of the angular setting in degrees of the polarizing

dichroic filter, and later converted to

dominant wavelength for reporting purposes.

Conditions. Eight conditions were

measured, combinations of the following

factors: presence and absence of reference light, large and small apertures,

and high and low luminance level. The

order in which the conditions were

presented was counterbalanced across

the eight observers.

Static thresholds. Static thresholds

were measured using the method of constant stimuli. The observer was

presented with a stimulus for 1 sec, and

then he/she responded "red," "green," or

Table 1

Stimuli for Chromatic Range Experiment

CIE Chromaticity Luminance

Dominant Excitation Coordinates (cd\rm2)

Color Wavelength Purity x y Low High

Red 603 nm 98% .630 .367 218 2184

White 578 nm 68% .439 .454 288 2878

Green 518 nm 48% .195 .565 542 5424

3

P B ND G L
.800-

500

4.

0

520

0

* Green

x = .195

y = .5 65

XD = 5l8nm

)0

1 3801

Fig. 3. The CIE Chron

locus of stimuli disp

nm/sec average). The observer was required to judge when the color of the

light appeared to change, and in which

direction, and then respond "more

0 550 green," "less green," "more red," or "less

red," at which point the variable

stimulus was extinguished. At the two

S575 extreme starting points, of course, the

direction of change could only be in the

Whi 0-""less" direction, resulting in a total of -439 600eih

e.439 0 600 eight combinations of starting point and

y = .454 Re SD= 578Snm Red direction of color change. These eight x = 63\0\

y - .367 -' 700 thresholds, measured in random order

D =603nm for each condition, were as follows: 518

nm to Less Green, 537 nm to More

Green, 537 nm to Less Green, 578 nm

toward Green, 578 nm toward Red, 597

I .8I nm to Less Red, 597 nm to More Red,

X. and 603 nm to Less Red. Typically three

to five measures were taken to deternaticity Diagram showing the mine each threshold, depending on the

layed by the variable light variability of the observer.

beam. The fixea beam snowed only the white

reference stimulus.

"neither." For each of the eight conditions, there were usually eight stimuli,

covering the range from one that appeared consistently red to one that appeared consistently green for that

observer. Each stimulus was presented

five times. The experiment was run in a

single session lasting about an hour.

Dynamic thresholds. The method of

limits was used to measure the dynamic

thresholds. Five starting points were

used: 518 nm -- the extreme green end

of the range, 537 nm -- moderately

greenish, 578 nm -- the white stimulus

the same as the reference light, 597 nm -

- moderately reddish, and 603 nm -- the

extreme red end of the range. The

stimulus was exposed, and after a random foreperiod of 0 to 5 sec, the experimenter rotated the variable dichroic

filter at one-half degree per second (0.5

The observers were told when their

judgment was in error. The errors were

recorded, but those data were not

averaged in the results for that

threshold; those trials were rerun later

in the session. No adjustment to the

data was made for observers' guesses

that happened to be correct, so the

results may be biased slightly towards

overestimating sensitivity. Each condition was run in a separate session, lasting about one-half hour.

RESULTS

Static Thresholds

Probit analysis was used to determine

the 95% response point for the red and

green thresholds for each observer

under each condition. These thresholds

were the points at which the observer

changed his/her response 95% of the

time from neither red nor green to either

4
just noticeably red or just noticeably

green. Thresholds varied widely, both

across observers as well as within observers, over the eight conditions. Some

lights that were called "red" by some observers were consistently called "green"

by others. For the eight observers, the

mean threshold across all conditions for

a green response was a light with a

dominant wavelength of 575 nm (SD =

6). For a red response, the wavelength

was 585 nm (SD = 5).

Mean red and green thresholds for

the three main pairs of experimental

conditions are shown in Figure 4. Absence of reference light, and lights of

higher luminance level and larger size,

all tended to shift both red and green

thresholds in the long-wavelength direction. It was hypothesized that the

586 --

584 --

582 4

0

a

Ii

580 4

578 4

576 -+

574 -

572 -

No

REF.

LIGHT

GI

-R

BRIGHT

REF.

LIGHT

G-

-G

presence of a white reference light

would make observers more sensitive to

small changes toward reddish or

greenish. To test this, as well as the effects of luminance level and aperture

size, repeated measures analyses of

variance (ANOVAs) were computed on

the threshold data for the following factors: 2 Conditions of Reference Light

(with and without) x 2 Luminance

Levels x 2 Aperture Sizes x 8 Subjects.

A separate ANOVA was computed for

the red and the green thresholds; the

results are shown in Table 2. In both

cases, the effect of Reference Light was

not significant, and Luminance Level

was significant. Aperture Size was significant for the green thresholds only.

A similar ANOVA was computed for

the differences between the red and

-R

LARGE

Dim G -

-G

-R

SMALL

-G

CONDITION

Fig. 4. Red and green static thresholds for the three experimental parameters (left to right): absence or

presence of reference light, luminance level, and aperture size. Mean data for eight observers.

5
Table 2

Summary of ANOVAs for Red and Green Static Thresholds

Threshold Source df F Probability

Red Reference Light 1,7 0.23 ---

Luminance Level 1,7 50.46 p < .001

Aperture Size 1,7 4.97 ---

Green Reference Light 1,7 2.07 ---

Luminance Level 1,7 77.52 p < .001

Aperture Size 1,7 37.45 p < .001

green thresholds. The only significance

found was for the effect of Reference

Light, F (1, 7) = 8.45, p < .05. Examination of Figure 4 shows, however,

that, contrary to expectations, the

presence of the reference light increased

the difference between the red and

green thresholds. The variables that

were manipulated in this experiment

therefore had no apparent effect on

reducing the red-green threshold differences that would indicate improved

sensitivity.

To get an approximation of the

neutral (not-red, not-green) point, we

calculated the midpoint of the red and

green thresholds for each observer by

condition. Averaged over all conditions,

mean neutral points for the observers

spanned a wide range, from 574 nm (SD

= 3.5) to 588 nm (SD = 3). The overall

mean midpoint was 580 nm (SD = 6),

slightly redder than the 578 nm

wavelength of the reference light determined prior to the experiments. A corresponding ANOVA on these midpoint

data yielded results comparable to those

of the red and green thresholds.

Dynamic Thresholds

A three-way repeated-measures

ANOVA, corresponding to those for the

static data, was computed for each of the

eight dynamic thresholds measured.

The presence of the reference light, as

with the static thresholds, never

produced a significant effect. In

general, the brighter stimuli and the

larger stimuli produced smaller

thresholds and improved performance,

although the effects were only significant at the longer-wavelength

thresholds. The ANOVA results for

these factors are summarized in Table 3.

The dynamic thresholds for the large

bright stimuli are plotted on the CIE

Chromaticity Diagram in Figure 5 in

terms of starting wavelength from

which the just noticeable difference was

measured. The arrows on the diagram

show the overall means across all eight

experimental conditions. Except for the

537 nm to Less Green threshold, the

thresholds are larger for the small dim

stimuli than for the larger brighter

stimuli. In addition, thresholds are

generally larger for thresholds in the

green region than in the red. The effects

of stimulus size, luminance, and

chromaticity found here are in keeping

6
Table 3

Summary of ANOVAs and Mean Errors for Dynamic Thresholds

Factor

Luminance Level Aperture Size

Mean

Threshold F P1 F P1 Errors (%)

518 nm to Less Green --- --- 22.4

537 nm to More Green --- --- 9.3

537 nm to Less Green --- --- 1.6

578 nm toward Green --- 6.9 .05 1.2

578 nm toward Red --- --- 0.0

597 nm to Less Red --- 13.7 .01 0.6

597 nm to More Red 10.3 .05 11.8 .05 1.6

603 nm to Less Red 157.3 .001 26.6 .005 9.3

Note. In all cases, df = 1,7

with results found earlier by other

methodologies (Brown, 1957; MacAdam,

1942; Wyszecki & Fielder, 1971).

Error percentages by condition were

calculated for each observer. The mean

errors for each threshold are presented

in Table 3. Observers made the largest

number of errors (22.4%) on the 518 nm

to Less Green threshold. Though they

could perceive a change, they could not

tell whether it was toward more green or

less green, since it was not apparent to

the observers that this was the extreme

green stimulus. Not quite as difficult,

but still producing substantial errors,

was the similar threshold at the extreme

red stimulus (603 nm to Less Red), and

the 537 nm to More Green threshold.

Some of these errors may be attributable

to the slower change in wavelength at

the extreme ends of the scale as the

polarized dichroic filter was rotated,

relative to the change at the middle of

its range. The slower change at the red

and green ends may have placed an additional memory or perceptual burden on

the observer, making the error rate

higher. ANOVAs corresponding to the

previous ones were computed on the

error percentage data for these three

thresholds. The only factor found significant was Luminance Level for the

537 nm to More Green threshold, E(1, 7)

= 9.9, p .05. Surprisingly, the brighter

stimulus produced 11.7% errors,

whereas the dimmer stimulus produced

only 6.9%. Perhaps the observers made

fewer errors with the dim stimuli because they were acting more conservatively in making more difficult

judgments.

DISCUSSION

Static Thresholds

Based on the results of this study, it

would appear very difficult to choose a

7
Je/

A?'

Ct.0

4N4t

AO

.t

AC'

'C'

0

A.

A.'C' Q

Q

'Cd 0

A.

N .. '7 4, . 'C'

4,

'C- Q

4',

'C'

'7 N0'C,

0 c. A. 'C'

4.

0

N A.0 'C,

4 , ;

I I I I I 1

•.200

3 • 300

4 . 400 I

• 500 0 . 600

X

Fig. 5. Dynamic thresholds for the larger brighter stimuli plotted on the 1931 CIE Chromaticity Diagram,

labeled in terms of dominant wavelength of starting point. Arrows indicate mean thresholds for all eight

stimulus conditions. Mean data for eight observers.

"white" light to indicate center of the

channel that would be immediately

recognized as white under a variety of

conditions by a large proportion of observers with normal color vision. When

looking at either individual or grouped

data, discrimination between white and

reddish or greenish colors appears quite

good. When comparisons are made

among different observers, however, it

is clear that wide and consistent differences exist in the judgment of hues.

Recently, Neitz and Jacobs (1986, 1990)

have documented the wide range of performance on a color matching task by a

large number of color normal observers.

In addition, studies have shown that significant shifts occur in the judgment of

hues with age (Schefrin & Werner,

1990) and even over relatively short

time periods within the same observer

(Laxar, Miller, & Wooten, 1988).

Choice of a more neutral (less yellowish) white may improve inter-observer agreement. Equipment

limitations precluded this. In any case,

however, individual differences would

8

.600 -T"

.500 -

y

.400 -

_ /

'4

4,o

.300 -+

I ! I
still exist. The literature contains many

examples of the variability of white

points, including differences due to exposure duration and stimulus size

(Jameson & Hurvich, 1951), as well as

physiological variables (Richards, 1967;

Wright, 1969). In this study, the large,

bright stimuli produced the smallest difference between the mean red and green

thresholds; that is, sensitivity to centerline position would be optimal. However, the neutral points (roughly, the

midpoints between the red and green

thresholds) for only three out of the

eight observers fell between the red and

green thresholds. These data show that

individuals have widely varying values

for what they call white. This suggests

to us that no observer looking at the reference light actually thinks of it as

white; it always looks either reddish or

greenish, and consequently does not do

much to help his/her performance. A

slightly different experimental task, in

which the observer was asked to directly

indicate "left," "center," or "right" channel position, rather than color, may

have shown the reference light to be

more useful in identifying center of

channel.

These results suggest that a

chromatic range beacon may not be an

appropriate device for displaying center

of channel position. Given the data from

the present simulations, we consider it

not meaningful to try to specify the sensitivity afforded by this type of beacon

for identifying center of channel position. It cannot be predicted whether,

from a brief glance, a vessel operator

could tell if he/she were on or slightly off

the channel centerline.

Dynamic Thresholds

As expected, discrimination of slowly

changing color stimuli proved much

poorer than measures of static discrimination found in the literature. As

shown in Figure 5, under the optimal

conditions of higher luminance level

and larger aperture size, there exist

seven just noticeable differences in the

range of colors tested. Let us assume a

nominal range 1219 m (4000 ft) long

with a channel width of 152 m (500 ft)

and the navigational beacon 610 m

(2000 ft) from the near end of the range

(see Laxar & Luria, 1990). If a singlestation range beacon were to display

these colors over the channel width at

the far end of the range, the observer's

sensitivity would be one-seventh of the

width, or 21.8 m (71.4 ft). This would

mean that the vessel would have to

move that distance across the channel

before the operator could determine that

the ship had moved, and in which direction (right or left). In a recent study of

two-station parallax ranges, Laxar and

Mandler (1989) found that observers

could perceive a change in horizontal offset of the near and far range lights of

approximately 1.5 minutes of arc. This

is equivalent to a sensitivity of 39 m

(128 ft) within a channel 152 m (500 ft)

in width. Under optimal conditions,

therefore, the color/saturation singlestation beacon may provide better sensitivity to motion across a channel than

present parallax displays. At the end of

the range near the beacon, however, the

colors, being displayed at the same

angles, would span only the central 51

m (167 ft) of channel width. In some instances, this may be impracticably narrow, and careful consideration would

have to be given to the dimensions of the

range for which an angular display

beacon could be used.

9
Aperture size may be more important

in determining performance than the

luminance levels tested here. It has

long been known that color discrimination becomes poorer with lights of

smaller subtense (Bedford & Wyszecki,

1958). With extremely small lights, discrimination becomes especially poor in

the blue-green region of the spectrum

(Willmer and Wright, 1945). The

smaller aperture, 1 arc min, would be

0.54 m (1.77 ft) in diameter and the

larger aperture, 3.5 arc min, would be

1.89 m (6.19 ft) in diameter at 1 nautical

mile distance. At greater distances, the

lights would have to be proportionately

larger, and may prove impractical for a

single-station beacon.

With the exception of the extreme

green end of the scale, errors on the

color/saturation dynamic thresholds

averaged lower than those found with

current two-station range indicators,

which were on the order of 11% (Laxar

& Mandler, 1989). The 22.4% error rate

found at the green extreme may be related to the relative lack of saturation of

that stimulus light, excitation purity of

48%, making it difficult to tell when it

was changing toward the yellowish

white. In the middle of the color range,

errors were virtually nil.

CONCLUSIONS

The color/saturation concept shows

promise for a single-station range

beacon for indicating lateral motion in a

navigational channel. For observers

with normal color vision, sensitivity was

better than with current two-station and

some alternative single-station range indicators, although errors were very high

at the extreme green end of the color

range. With the colors of lights tested,

however, it was unclear that such a

beacon would perform adequately for

signaling when the vessel was on or

near the centerline of the channel. Further study with a more saturated green,

a more neutral white, and a longer

wavelength red would provide further

information on the adequacy of a

color/saturation single-station range indicator. The colors would also have to be

carefully chosen and tested to ensure

minimal confusion by color defective observers, estimated to comprise over 8%

of the male population (Wyszecki &

Stiles, 1982).

ACKNOWLEDGMENT

The authors wish to thank Ms. Kelly

Johnson for her help in observing, and

collecting and analyzing data.

REFERENCES

Bedford, R. E., & Wyszecki, G. (1958).

Wavelength discrimination for point

sources. Journal of the Optical

Society of America. 48. 129-135.

Brown, W. R. J. (1957).

crimination of twelve

Journal of the Optical

America, 47, 137-143.

Color disobservers.

Society of

Jameson, D., & Hurvich, L. M. (1951).

A psychophysical study of white. II.

Neutral adaptation. Area and duration as variants. Journal of the Optical Society of America, 41, 528-536.

Jameson, D., & Hurvich, L. M. (1955).

Some quantitative aspects of an opponent-colors theory. I. Chromatic

responses and spectral saturation.

Journal of the Optical Society of

America, 45, 546-552.

10
Jones, L. A., & Lowry, E. M. (1926).

Retinal sensibility to saturation differences. Journal of the Optical

Society of America, 13, 25-37.

Laxar, K., & Luria, S. M. (1990). Frequency of a flashing light as a navigational range indicator (Report No.

1157). Groton, CT: Naval Submarine

Medical Research Laboratory.

Laxar, K., & Mandler, M. B. (1989).

Navigation performance using parallax range lights (Report No. 1149).

Groton, CT: Naval Submarine Medical Research Laboratory.

Laxar, K., Miller, D. L., & Wooten, B. R.

(1988). Long-term variability in the

spectral loci of unique blue and unique yellow. Journal of the Optical

Society of America A, 5, 1983-1985.

(NSMRL Report No. 1107)

Luria, S. M. (1990). Perception of temporal order of flashing lights as a

navigation aid (Report No. 1155).

Groton, CT: Naval Submarine Medical Research Laboratory.

MacAdam, D. L. (1942). Visual sensitivities to color differences in

daylight. Journal of the Optical

Society of America, 32, 247-274.

Martin, L. C., Warburton, F. L., & Morgan, W. J. (1933). The determination

of the sensitiveness of the eye to differences in the saturation of colours.

Special Report Series No. 188 (pp. 1-

42). London: Great Britain Medical

Research Council.

Neitz, J., & Jacobs, G. H. (1986).

Polymorphism of the longwavelength cone in normal human

colour vision. Nature, London, 323,

623-625.

Neitz, J., & Jacobs, G. H. (1990).

Polymorphism in normal human

color vision and its mechanism.

Vision Research, 30,621-636.

Priest, I. G., & Brickwedde, F. G.

(1938). The minimum perceptible

colorimetric purity as a function of

dominant wavelength. Journal of the

Optical Society of America, 28, 133-

139.

Richards, W. (1967). Differences among

color normals: Classes I and II. Journal of the Optical Society of America,

57,1047-1055.

Schefrin, B. E., & Werner, J. S. (1990).

Loci of spectral unique hues

throughout the life span. Journal of

the Optical Society of America A, _,

305-311.

Willmer, E. N., & Wright, W. D. (1945).

Colour sensitivity of the fovea

centralis. Nature, 156, 119-121.

Wright, W. D. (1969). The measurement of colour. New York: Van

Nostrand Reinhold.

Wyszecki, G., & Fielder, G. H. (1971).

New color-matching ellipses, Journal

of the Optical Society of America, 61,

1135-1152.

Wyszecki, G., & Stiles, W. S. (1982).

Color science (2nd ed.). New York:

Wiley.

11
UNCLASSIFIED

SECURITY CLASSIFICATION OF THIS PAGE

Form Approved

REPORT DOCUMENTATION PAGE OMB No. 0704-0188

la. REPORT SECURITY CLASSIFICATION lb. RESTRICTIVE MARKINGS

UNCLASSIFIED

2a. SECURITY CLASSIFICATION AUTHORITY 3. DISTRIBUTION /AVAILABILITY OF REPORT

2b. DECLASSIFICATiON/DOWNGRADING SCHEDULE Approved for public release; distribution

unlimited.

4. PERFORMING ORGANIZATION REPORT NUMBER(S) 5. MONITORING ORGANIZATION REPORT NUMBER(S)

NSMRL Report # 1163

6a. NAME OF PERFORMING ORGANIZATION 6b. OFFICE SYMBOL 7a. NAME OF MONITORING ORGANIZATION

Naval Submarine Medical (If applicable) Naval Medical Research and Development

Research Laboratory Command

6c. ADDRESS (City, State, and ZIP Code) 7b. ADDRESS (City, State, and ZIP Code)

Naval Submarine Base New London National Naval Medical Command

Groton, CT 06349-5900 Bethesda, MD 20889-5044

8a. NAME OF FUNDING/SPONSORING 8b. OFFICE SYMBOL 9. PROCUREMENT INSTRUMENT IDENTIFICATION NUMBER

ORGANIZATION U. S. Coast Guard (If applicable)

Research & Development Center I

8c. ADDRESS (City, State, and ZIP Code) 10. SOURCE OF FUNDING NUMBERS

Avery Point PROGRAM PROJECT TASK WORK UNIT

ELEMENT NO. NO. NO. ACCESSION NOSMIPR Z51100 9 0002

11. TITLE (Include Security Classification)

"(U) The effectiveness of a color beacon as a navigational range indicator

12. PERSONAL AUTHOR(S)

LAXAR, Kevin, & LURIA, S. M.

13a. TYPE OF REPORT 13b- TIME COVERED 114. DATE OF REPORT (Year, Month, Day) 115. PAGE COUNT

Interim FROM 4/Q9 TO 109Q 0 1990 October 19 12

16. SUPPLEMENTARY NOTATION

17. COSATI CODES 18. SUBJECT TERMS (Continue on reverse if necessary and identify by block number)

FIELD GROUP SUB-GROUP Aids to navigation; leading lights, range lights;

lateral sensitivity, saturation discrimination;

h,, discrimination; color perception

19. ABSTRACT (Continue on reverse if necessary and identify by block number)

We evaluated the effectiveness as an aid to navigation a single-station beacon which

was white when viewed from the centerline of a channel and became increasingly red or

green when viewed from off center to the right and left. First we measured the

observers' ability to determine whether a light was white, reddish, or greenish. A wide

range of colors, from 575 nm to 585 nm, were judged to be white, making it difficult to

specify a beacon that would adequately signal conter of channel. Second, we measured'

the ability of the observers to detect a change in color for slowly changing stimuli.

There were seven just noticeable differences in the range of color investigated. This

would provide a sensitivity of 21.8 m (71.4 ft) over a 152 m (500 ft) wide channel.

Measurements were taken with and without a "white" reference light. Under no condition

did the reference light improve performance. For changing stimuli, however, those that

were brighter or larger provided better sensitivity than those that were small or dim.

20- DISTRIBUTION/AVAILABILITY OF ABSTRACT 21. ABSTRACT SECURITY CLASSIFICATION

flUNCLASSIFIED/UNLIMITED EJ SAME AS RPT. C3 DTIC USERS UNCLASSIFIED

22a. NAME OF RESPONSIBLE INDIVIDUAL 22b. TELEPHONE (Include Area Code) 22c. OFFICE SYMBOL

iSq,•n T)- Mnnt-v_ Piuh1ien-t-4nn.Q Offit, (0'9 449-3967

DD Form 1473, JUN 86 Previous editions are obsolete.

S/N 0102-LF-014-6603

SECURITY CLASSIFICATION OF THIS PAGE

UNCLASSIFIED
SECURITY CLASSIFICATION OF THIS PAGE

DD Form 1473, JUN 86 (Reverse) SECURITY CLASSIFICATION OF THIS PAGE