NBSIR 75-663 0=0

Color Requirements for the

Marking of Obstructions

Robert L. Booker

Illuminating Engineering Group

Optical Radiation Section

Heat Division

Institute for Basic Standards

National Bureau of Standards

March 1975

Final Report

Prepared for Federal Aviation Administration

Systems Research and Development Service

Washington, D. C. 20553
•A .
NBSIR 75-663

COLOR REQUIREMENTS FOR THE

MARKING OF OBSTRUCTIONS

Robert L. Booker

Illuminating Engineering Group*

Optical Radiation Section

Heat Division

Institute for Basic Standards

National Bureau of Standards

March 1975

Final Report

*The work described herein was accomplished while the author was in the Sensory Environment Section, Center for Building

Technology, Institute for Applied Technology.

Prepared for Federal Aviation Administration

Systems Research and Development Service

Washington, D. C. 20553

U. S. DEPARTMENT OF COMMERCE, Frederick B. Dent, Secretary

NATIONAL BUREAU OF STANDARDS, Richard W. Roberts. Director

CONTENTS

Page

Abstract iv

1. Introduction 1

2. The Problem 1

3. Visual Observations 3

3.1 Ground Observations in Washington Area 3 3.2 Air Observations in Washington Area 4

3 . 3 Air Observations in Surrounding Area 4

4

4. Analysis of Flight Observations

5. Colorimetry of Paint Chips 10

6. Discussion of Previous Experiments 11

7. Recommendations and Discussion 14

8. Field Implementation 16

REFERENCES 19

APPENDIX A - Group on First Field Trip 20

- i
LIST OF FIGURES

Figure No. Page

1. Portion of Chromaticity Diagram Showing

Coordinate Locations of Paint Chips from Towers

and Various Chromaticity Boundaries for Surface

Orange 12

2. Eight Coordinate Positions of Color Chips

Proposed for Inspection of In-Service Orange

Painted Surface 17

- 11 -
LIST OF TABLES

Table

No. Page

1. Chromaticity Coordinates and Luminance Factor (Reflectance)

of Paint Chips from Towers in Washington Metropolitan Area... 3

2. Comments Resulting from Helicopter Flight Viewing Towers in

Washington Metropolitan Area on June 4, 1974 5

3. Chromaticity Coordinates, Luminance Factors (Reflectance) of

Paint Chips, and Comments Relating to Towers Observed During

DC-3 Flight on May 17, 1974 6

4. Description of Six Colors Used by Middleton 13

5. Chromaticity Coordinates (Source C) of Color Chips Proposed

for Inspection of In-Service Orange Painted Surfaces 18

- iii -
ABSTRACT

Present methods and problems associated with the

surface marking of obstructions to aviation, such as tall towers, are discussed. The correlation of subjective

evaluations of appearance, from both ground and air

observations, with the physical characteristics of the

orange-painted sections of selected towers is described.

Recommendations regarding the in-service appearance of

orange paint consist of expanded chromaticity limits in

combination with specific restrictions on reflectance.

A suggested method of field implementation consists of

using color tolerance charts displaying colored squares

which depict the limit of the chromaticity and reflectance

requirements.

IV -
Color Requirements for the Marking of Obstructions

1 . INTRODUCTION

The Federal Aviation Administration requires that all obstructions, which pose a potential hazard to aircraft, be marked

in a specific manner. Included in this category are towers

rising 200 feet or more above the established terrain. They must

be painted in alternating bands of white and orange in accordance

with the provisions of Advisory Circular 70/7460-1. The purpose

of this requirement is to increase the conspicuity of the towers

when viewed from the air during daylight hours. Under certain

viewing conditions, a tower's painted pattern is recognizable

before its outline.

It should be pointed out that the color aviation orange is

used for its proven characteristic of conspicuity under a wide

range of environmental conditions. It is unimportant that an aviator identify its orange color as such. It is only important

that he notice the presence of an object painted with it. It is

also for reasons of increased conspicuity that the luminance

factors (reflectances) of the white and orange paints used in

painting the towers are markedly different. Aviation surface

orange has a reflectance of approximately 14% while aviation

white is about 88% when the paints are fresh.

In order to control the orange color of towers, the FAA

published an "Aviation Surface Orange Color Tolerance Chart" in

May, 1971. The chart displays a grouping of seven orange colored

squares including a target color in the center and six surrounding

tolerance limit colors which differ from the target color in

varying degrees of hue, lightness, or saturation. The chart has

two vertical openings which allow an orange surface to be visually

evaluated when the chart is placed upon it.

Information on the reverse sides of the color tolerance

chart lists both the CIE data (Source C) and the Munsell notation

for each of the seven orange squares. A brief explanation of the

Munsell System is given as well as an explanation of the usage of

the chart. Two available paints which meet the requirements of

the specification are also listed.

2. THE PROBLEM

The Color Tolerance Chart is an effective means of controlling

the color of newly painted towers. However, the color of a newly

painted exterior surface soon begins to deteriorate due to action

- 1 -
of the weather and elements. The orange painted sections of the

towers change and soon reach a point where they are outside the

limits of the color tolerance chart. FAA Advisory Circular AC

70/7460-1 is not specific in that it recommends that "...

surfaces should be repainted whenever the color changes noticeably

or its effectiveness is impaired by scaling or chipping." A

recommendation of the International Civil Aviation Organization

, (ICAO) is similar in tone — "The specifications of surface

colors apply only to freshly colored surfaces. Colors used for

surface markings usually change with time. Due diligence should

be exercised to ensure th^t surfaces are renewed whenever they

have changed color noticeably," The problem is compounded because

a paint's useful life usually extends beyond its chromatic life.

In other words, the paint will continue to protect the tower's

surface even after the paint has lost most of its chromatic

qualities.

Consequently, the FAA is considering the use of additional color

tolerance charts, to display acceptable limits of fading, for use in

determining when a tower should be repainted.

3. VISUAL OBSERVATIONS

Three separate field trips were conducted in order to

evaluate the appearance of various towers.

3 . 1 Ground Observations in Washington Area.

The first field trip, which consisted of ground observations,

occurred on Noven±)er 19, 1973, when a group comprised of 10

' . individuals from the Federal Aviation Administration, Federal

Communications Commission, and the National Bureau of Standards

(See Appendix A) visited seven tower sites in the Washington, D. C. area

.

As the towers were visited, each of the participants from

the FAA and FCC was questioned by the senior NBS participant

regarding his opinion of the appearance (color) of the painted

orange surfaces. A seven-point scale was used in ranking the

towers with seven corresponding to the most satisfactory rating

and one to the least satisfactory rating. These subjective

evaluations were recorded and later used in correlating the

visual assessments with the physical data obtained from the

paint chips which were gathered at most of the sites c These

results are presented in Table 1 and are discussed more fully

in Section 5 of the report. An interim report was issued

regarding these findings [1]

.

- 2 -
TABLE 1 Chromaticity Coordinates and Luminance

Factor (Reflectance) of Paint

Chips from Towers in Washington Metropolitan Area

Average of the

Tower X y. X* Observers' Ratings

A - WDCA 0.521 0.360 22.2 6.1

.528 .364 21.3

B - WMAL .510 .356 16.1 6.0

.504 .355 15.3

.470 .351 15.1

C - AT&T .477 .351 21.2 4.5

.479 .352 21.2

.461 .347 16.4

D - WRC .5 39 .359 9.9 3.2

.477 .367 11.7

.492 .364 10.4

E - PEPCO .459 ' .345 14.4 3.1

.441 .348 21.9

F - WTOP-2 .601 .349 19.77 6.4

.578 .354 19.77

- 3 -
3. 2 Air Observations in Washington Area

These same towers were later observed from the air during

;. a helicopter flight the afternoon of June 4, 1974. Some

additional structures along the flight path were also observed.

The comments of the three NBS observers are presented in Table 2.

3 . 3 Air Observations in Surrounding Area.

A different group of towers, consisting of 12 locations

over a 4-state area, was observed from a DC-3 aircraft,

operated by the FAA, on May 17, 1974. After locating a particular tower, the pilot usually circled at close range.

Occasionally the pilot was asked to circle at longer

distances, ranging up to 4 miles. The observations

presented in Table 3 represent those of the NBS

participants.

4. ANALYSES OF FLIGHT OBSERVATIONS

Circling the towers during the DC-3 flight served to illustrate

the degree to which a tower's conspicuity can vary as a function of

viewing angle and viewing conditions. For example, in the up-sun

direction, the towers are silhouetted against a brighter sky background and, as such, have a negative contrast -- see Middleton [2]

.

Under these conditions, their contrast with the sky is almost independent of the color or the condition of the paint. Viewing up- sun is a condition where the tower is viewed against a bright,

illuminated sky, with the sun far enough from the line of sight so that it is not a glare source.

Down-sun is used to describe viewing conditions where the

sun is behind the observer as he views the tower. Under these

conditions, the white of the tower usually appears to be much

more luminous than its background and hence is highly conspicuous

and the orange is conspicuous as a chromatic signal. However, if

under down-sun viewing conditions, the background of the tower is a sun-lighted cloud, the contrast between the white of the tower

and the background will be very low, and the white will often not

be visible.

The foregoing discussion of up-sun and down-sun tower

visibility assumes a sky background. The situation is obviously

different for a terrestrial background, which is much darker.

Viewing up-sun against a shaded terrestrial background such

as hills or trees, the tower appears dark against its background,

since the sun is behind the tower. Under these conditions, colors

are difficult to distinguish and the chromatic aspects of orange

- 4

-
TABLE 2

Comments Resulting from Helicopter Flight

Viewing Towers in Washington Metropolitan Area

on June 4, 1974

Area/Tower Comments /Addp;i r^nfp

Andrews AFB - glide path shelter and other small buildings - very good

+- Y" 3 O TTl 1 C G <^tTtO +* O V" C +" a n /*1 — 1 1 r-\ -J ^/~«

o

Y~\ 3 1 O

— water tower - good to very good, depending

on angle of view

Anacostia various smokestacks - all had faded paint - appearcince with down-sun viewing acceptable

N. W. Washington highly visible in silhouette as seen from

(WRC, WTOP, WTTG) Georgetown - white almost invisible from

(-nam tsriage area vaoouL. z>u to sun^

PEPCO terrestrial background-being repainted - much

improved

WMAL 4 guyed towers - good appearance - terrestrial

background - white better than orange

WMAL (old) self-standing - appeareince at limit of acceptability

WRC/AM 4 slender guyed towers - not so good - towers

present small surface area - paint may be OK - background includes brick buildings

WJMD short tower in golf course - terrestrial background - very good from all angles of view

WDCA candelabra-River Road - poor - lacks chromatic

appearance from all angles of view

WTTG & WTOP good - shorter WTOP tower has been repainted - wave guides not painted

WRC/TV poor - orcinge appears very dark

American University somewhat better than WRC/TV - near limit of

acceptability

Virginia group of 3 towers - microwave tower acceptable - others poor - tallest, self-standing, has desaturated.

yellowish orange - nearby water tower excellent

Note - See Table 1 for chromaticity coordinates of orange paint on Washington

area towers

- 5 -
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surfaces are not apparent. The white portion in a tower's painted

pattern becomes its distinguishing factor, since it is the only

part that stands out against the dark background. The necessity

for a white paint of high reflectance under these circumstances

is obvious.

Viewing down-sun against a terrestrial background does

not present any special problems. The combination of terrestrial

background and direct illumination on the viewed surface of the

tower tends to make the tower very conspicuous, with good coloring,

even if the paint is faded.

Up-sun and down-sun viewing are, of course, only two of the

many possible viewing angles. When consideration is given to the

variations that occur in backgrounds, a truly large number of

viewing situations is possible. Because of this high number of

combinations of viewing conditions which must be accommodated,

maintenance of a pattern having a high reflectance in white

and high chromaticness in orange is essential.

Tower number 12, in Richmond, is a good case for the use of lights. From some angles of view, its appearance will have

a seasonal variation, depending on the extent of foliage on the

terrestrial background. Since our observations took place in

mid-May, the trees were leafed-out and provided a good visual

background. However, from some angles of view, the background

was a mixture of concrete pavement and red brick buildings,

which effectively camouflaged the tower. This latter condition

is more predominant in the winter months, when the trees are without leaves.

Towers number 11 and 11a showed the distinct advantage

of (apparently) new paint. Their appearance was greatly en- hanced, on a comparative basis, by the saturated colors of the

orange paint.

Generally speaking, there are 3 separate ways in which a tower's appearance is likely to deteriorate:

a) the orange paint can fade (desaturate) and become

lighter.

b) the orange paint can get darker and desaturate

towards neutral.

c) both the orange and white paint can get darker while

maintaining the same chromaticity (hue and chroma)

.

- 8 -
The first and second conditions characterize the towers

viewed from the ground during the earlier field trip, based on

the colors of the paint chips [1]

As previously mentioned, comments relating to the helicopter

flight are presented in Table 2. Towers supported by guy wires

are identified as such in the comments. Guyed towers are more

slender and, depending on the viewing distance, are frequently

less conspicuous than self-standing towers of the same height,

which present a larger painted surface to an observer.

Circumstances require special examination of the data and

comments regarding the WDCA tower. The data in Table 1 show a high rating from the ground observers and fairly high saturation

for an in-service orange paint. In view of this, the comments

resulting from the helicopter flight. Table 2, that the appearance

of the WDCA tower was "poor" and "lacks chromatic appearance from

all angles of view" would seem to be contradictory. However, the

ground observations had revealed that the interior exposed surfaces

of the WDCA tower had not been painted and had a deteriorated

appearance. The ground observers based their evaluation (rating)

of the tower's appearance upon those surfaces that were painted.

The consequences of this were borne out in the ultimate test,

appearance from the air. This example should be ample proof for

the necessity of painting all exposed surfaces of skeletal structures.

The new (100-foot) stripes are much better than the older

40-foot wide stripes in making a tower conspicuous. Consideration

should be given to synchronizing the painted patterns of towers

in close proximity to one another despite differences in height.

For instance, if two or more towers of differing heights are located within an area of one-half mile or less in diameter,

then the band width for all towers would be based on the height

of the tallest tower, as specified in AC 70/7460. However, the

width of the uppermost orange band of the shorter tower should be

adjusted, as appropriate, to insure that the top of the tower is

painted orange.

When the band widths of such towers are not arranged to

coincide with one another, under some angles of view the towers

can line up in such a manner that, while not obscuring one

another, the combined patterns present a mottled mixture of

orange and white that makes the towers less conspicuous.

- 9

-
5. COLORIMETRY OF PAINT CHIPS

Orange paint chips were gathered at six of the tower sites

during the observations in the Washington metropolitan area to be

used in correlating the subjective evaluations of the towers'

appearance with a physical description of the orange paint. The

paint chips were gathered from the base of the towers.

Subsequent to the DC-3 flight, appropriate tower operators

were contacted requesting that orange paint chips from the base of

the tower be sent to us. Information was also requested regarding

the date and type of paint used during the most recent painting of

the tower.

Because the fragile condition of the chips and their non-viniform

surface contours made them unsuitable samples for spectrophotometry,

the paint chips were visually evaluated by NBS personnel under a controlled visual environment and their color described using the

Munsell renotation system. The color designations were made using

45° illumination and perpendicular viewing. The source of illumination was a system using Macbeth Nor lite D7500 fluorescent lamps.

The Munsell renotation was then converted to CIE notation using the

tables and charts in Wyszecki and Stiles [3]

.

Every chip obtained from each site was not evaluated. Chips were selected for evaluation which were noticeably different from

others gathered at the same site. In some cases, only a small

portion of a chip was evaluated.

Since the conversion charts are based on CIE Illuminant C,

and the paint chips were initially described using a D7500 source, an adjustment factor was obtained to account for the differences in

chromaticity due to the different sources.

In order to obtain an adjustment factor, ten colored scimples

were selected from Federal Standard 595 on the basis that their

chromaticity coordinates were in the same general range as those

of the chips from the tower sites. The spectral reflectance properties

of each of these 10 samples was then obtained using a recording

spectrophotometer automated with digital interface equipment.

Chromaticity coordinates were then computed for both Source C and

D7500 illuminants. Source C has a correlated color temperature of

6770 K and is representative of the spectral energy distribution

of overcast skylight. A comparison of the results for the two

sources provided adjustment factors which were then applied to

convert the D7500 results to Source C results.

The adjusted chroma ticities (Source C) are listed in

Tables 1 and 3. Also tabulated in Table 3 are the averages of

the individual numerical ratings of the appearance (color) of the

- 10 -
towers visited during the initial ground observations, obtained as

a result of the subjective evaluations.

The chromaticity coordinates listed in Tables 1 and 3 are plotted in figure 1, a portion of a CIE chromaticity diagram.

Also shown are the boundary limits for ICAO orange and FAA

aviation surface orange. The so-called boundary limits for FAA

aviation orange were obtained by joining with straight lines the

coordinate points of the hue and chroma (saturation) limit

colors on the color tolerance chart. It is interesting to note

that the H-(red limit) point plots outside of the ICAO limits.

The possibility exists that the orange paint at the base of

a tower, from which paint chips were obtained, was not representative of the upper portions of the tower. However, results obtained

through colorimetry of the paint chips correlated well with the

ground and in-flight field observations. It was considered not

feasible to attempt obtaining paint chips from higher portions of

the tower.

6. DISCUSSION OF PREVIOUS EXPERIMENTS

Middleton's work on the conspicuity of orange surface colors [4]

is pertinent to the present problem. Middleton used six individual

targets, six foot square, at distances from 4 1/4 miles to 6 1/4 miles.

The panels faced south and were therefore illuminated by the sun when

it was not obscured by clouds. Observations took place in all seasons

and the visual backgrounds included snow, vegetation which varied

seasonally, light brown grass, fresh green grass, and the forest. The

observers indicated the order of conspicuity of the six panels as a chromatic signal. A description of the six colors used by Middleton

is given in Table 4.

One of the colors. No. 3, corresponds very closely to FAA aviation

orange. The first five colors formed a series ranging from bright

yellow to a deep reddish orange; the sixth was designed to be similar

in hue to aviation orange but of lower saturation, to correspond to a weathered surface of that paint.

The results showed that color No. 1, a bright yellow, is totally

unsatisfactory as a chromatic signal, despite being very conspicuous

against dark backgrounds. When seen from a distance, this color frequently resembled that of a patch of sand or light soil.

Against the forest background the order of conspicuity of colors

2 to 5 was the order of their reflectances. The performance of No. 6,

designed to simulate weathered or slightly soiled aviation orange, was

the poorest.

Against the snow background, aviation orange. No. 3, was the

superior color. Color No. 6 again made the poorest showing.

- 11 -
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TABLE 4

Description of Six Colors Used by Middleton

No, Composition

Reflectance

Y

Chromaticity

Coordinates

X y

Munsell

Renotation

H V/C

1 Medium Chrome

Yellow

0.512 0. 501 0.471 1.5Y 7.5/15.2

2 Aviation Orange

and Med. Chrome

Yellow

3 Aviation Orange

4 Aviation Orange

and Toluidine

Red

5 Aviation Orange

and Toluidine

Red

6 Aviation Orange

and Light Chrome

Red

,226 573

086

121

.654

407 3YR 5.3/15.0

142 .608 .363 0.5YR 4.3/14

114 .620 .339 9R 3.9/16

321 8R 3.4/15

588 .373 lYR 4.0/12.4

- 13 -
Color No. 3 maintained a slight superiority against the

grass background.

Middleton concluded that aviation orange. No. 3, was the

most conspicuous color among those chosen when the whole range of

natural backgrounds was taken into account, although a lighter

and yellower color was more conspicuous against a forest background.

Middleton had predicted this earlier on a theoretical basis [5]

.

His second conclusion was that it is essential to keep this

color clean and fresh, or in other words to maintain a high

chroma. Color No. 6, which gave poor results throughout, could

easily pass for a moderately weathered specimen of aviation

orange. Middleton considered his paper as documenting the.

necessity for maintaining these orange paints in very good

condition.

It should be noted that Middleton 's conclusion, regarding

the use of yellow against a forest background, was based on the use of a single conspicuous color as a signal. It is precisely

for the reason that obstructions are viewed against a variety of

backgrounds that the FAA-prescribed marking pattern consists of

alternating orange and white. The white is conspicuous in

situations where the orange is deficient, i.e., against a dark

forest background.

In a separate but related study, Judd and Yonemura [6]

concluded that international orange is more conspicuous than

black against a dark-foliage surround; and black is more conspicuous

than international orange for a light-foliage surround. For

average foliage international orange is more conspicuous at large

angular subtense (greater than 10 minutes of arc) ; and black is

more conspicuous at small subtense. The virtue of international

orange is that it is fairly conspicuous against all foliage

backgrounds.

7'. RECOMMENDATIONS AND DISCUSSION

It is recommended that the FAA adopt limit boundaries to

determine the acceptability of the color of in-service orange

painted obstructions. The acceptable area of chromaticities is

bounded by the spectrum locus and the following boundaries as plotted on the 1931 CIE chromaticity diagram:

y 0 .lOOx + 0.285 (red boundary) (1)

y 0.862 - X (white boundary) (2)

y 0.220X + 0.250 (yellow boundary) (3)

- 14 -
The coordinates of the points of intersection of the white

boundary with the red and yellow boundaries are x = 0.525, y

= 0.337 and x = 0.502, y = 0.360. These "in-service" boundaries

are plotted on figure 1. The solid lines are the existing

boundaries for ICAO orange. The dashed lines represent the

additional limits recommended in this report. The red and yellow

in-service boundaries recommended for faded orange are extentions

of the existing red and yellow limits of ICAO orange. These

boundaries approximate the constant hue lines between ICAO orange

and CIE Source C.

Associated with the expanded limits on chromaticity are upper and lower limits on the reflectance of the orange paint.

The maximum reflectance permitted is Ymax = 0.21. The minimum

reflectance allowed varies according to the location of the

sample within the orange boundaries. This limitation is represented by the equation

Y . = 0.452 - 0.541X (4) min

which requires minimum reflectances which vary from 0.18 for the

minimum saturation permitted to 0.10 for saturated colors at the

spectrum locus.

The area delineated by the dashed lines, used in conjunction

with the limitations on reflectance, includes the chromaticities

of the paint chips from those towers regarded as acceptable or not deteriorated enough to be regarded as unacceptable. Requiring

the reflectance Ymin ^ function of the chromaticity co- ordinate X permits the continued in-service use of those few

relatively desaturated orange surfaces whose reflectance was

such that their appearance was not unacceptable.

At first glance^ the recommended boundaries for in-service

orange may seem to allow colors which are too desaturated.

However, these boundaries are consistent with the visual data

obtained — to use more restricted boundaries would be tantamount

to ignoring the results of the observations.

As noted earlier, it is unimportant for an aviator to

identify the orange color as such. This checks well with the

observations where it seems that the chromaticness of the orange

per se is not important in establishing the acceptability of a tower's appearance. In this regard, the conclusions stated in

this report differ from those of Middleton described earlier.

As discussed in Section 6, Middleton 's conclusion was based on the use of a single conspicuous color as a signal.

- 15 -
8. FIELD IMPLEMENTATION

In order to facilitate the field evaluation of in-service

orange paint, it is recommended that a pair of color tolerance

charts, designated as ^maiX ^min be developed, similar to

the presently available "Aviation Surface Orange Color Tolerance

Chart" used for new paint- Each chart would display non-glossy

color chips (squares) with chromaticity coordinates at the eight

locations indicated on figure 2. Each of the eight chips on the

chart would have a reflectance of 0.21 corresponding to the

maximum allowable reflectance. The eight chips on the Y^in

chart have reflectances as a function of their position computed

using equation 4. The chromaticity coordinates, and equivalent

Munsell notation, of the eight ^max chips and the eight '^x^^.n chips are listed in Table 5.

The spacing of the color chips along the red and yellow

boundaries was obtained through the use of a 1960 CIE uniformchromaticity-scale diagram (UCS) . After the red and yellow

boundaries were plotted on the UCS diagram, points were located

that divided these boundaries into four equal portions between

the white boundary and the spectrum locus. These points were

then transformed back into the 1931 CIE system and, together

with the two intersection points on the white boundary, provide

the locations of the eight proposed color chips, as shown in

figure 2 .

^

When using the new charts to evaluate in-service orange

painted surfaces, an acceptable orange surface would be one

redder than the colors lying along the yellow boundaries, yellower

than the colors lying along the red boundaries, more saturated

than the colors forming the white boundaries, no lighter than

its nearest color match on the Yj^^j^ card, and no darker than its

nearest color match on the Yjnin card.

16 -
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18 -
REFERENCES

1. Booker, R. L., Interim Report on the Marking of Obstructions,

NBS Report of Test, March 18, 1974.

2. Middleton, W.E.K. , Vision Through the Atmosphere, Univ. of Toronto

Press, 1952.

3. Wyszecki, G. and Stiles, W. S. , Color Science, Wiley, New York

1967.

4. Middleton, W.E.K. , A Study of the Conspicuity of Orange Surface

Colors, Illuminating Engineering, 95, 1952,

5. Middleton, W.E.K., The Colors of Distant Objects, JOSA 40, 373,

1950.

6. Judd, D. B. and Yonemura , G. T. , Target Conspicuity and Its

Dependence on Color and Angular Subtense for Gray and Foliage

Green Surrounds, NBS Report 10-120, November 1969.

- 19 -
APPENDIX A

List of Individuals Comprising Group

Which Visited Tower Sites in Washington, D. C. Area on November 19, 1973

Name

Walter Fisher

Stanley Kingham

Joseph Scarlata

Gerald Gibson

Addison Fowler

Joseph Thomas

Carlos Roberts

Charles Douglas

Robert Booker

Gerald Howett

Organization

FAA-ARD-320

FAA-AAT-242

FAA-AAT-242

FAA-AFS-460

FAA-AAS-550

Federal Communications

Commission

Federal Communications

Commission

National Bureau of

Standards

National Bureau of

Standards

National Bureau of

Standards

USCOMM-NBS-OC - 20 -
NBS-114A (REV. 7-73)

U.S. DEPT. OF COMM.

BIBLIOGRAPHIC DATA

SHEET

1 PIIMI If ATIONJ OR R K POH T NO

NBSIR 75-663

V liy-\ti t A f /~ ^ c c I r\n 4,* VJOV I /ii. C C 3 ?> 1 (Jll No.\ n. ^ f t r\ t n t c A/^/~<*ccir^n M

Color Requirements for the Marking of Obstructions

5. Publication Date

6« Perforrning Organization Code

7. AUT}10RfS) Robert L. Booker

8. Performing Organ. Report No. NBSIR 75-663

y. PhKrUKMlNCi ORG AN 1 ION .NAMh AND AlJlJRhSS

NATIONAL BUREAU OF STANDARDS

DEPARTMENT OF COMMERCE

WASHINGTON, D.C. 20234

10. Project/Task/Work Unit No.

11. Contract /Grant No.

' ^* --'JJL'lIoUt '"f> ^ ' ^cllli£.£lLICJil l^dlllC allU '-UlIlL/ltrltr '»Ll(jrt:SS (•Jl/Crtrl, \mf J ly , ^ lOlC , w f » ^ Federal Aviation Administration

Research and Development Service

Washington, D. C. 20553

13. Type of Report & Period Covered

Final, March 1975

14. Sponsoring Agency Code

15. SUPPLEMENTARY NOTES

16. ABSTRA(;T (A 200-word or less factual surrunary of most si^ificant information. If document includes a significant

bibliography or literature survey, mention it here.)

Present methods and problems associated with the surface marking of obstructions

to aviation, such as tall towers, are discussed. The correlation of subjective

evaluations of appearance, from both ground and air observations, with the physical

characteristics of the orange-painted sections of selected towers is described.

Recommendations regarding the in-service appearance of orange paint consist of

expanded chromaticity limits in combination with specific restrictions on reflectance.

A suggested method of field implementation consists of using color tolerance charts

displaying colored squares which depict the limit of the chromaticity and reflectance

requirements

.

17. KEY WORDS (six to twelve entries; alphabetical order, capitalize only the first letter of the first key word unless a proper name; separated by semicolons)

Aviation orange paint; color marking of obstructions; obstruction marking; visibility of towers.

18. AVAILABILITY Unlimited

Ix} For Official Distribution. Do Not Release to NTI.S

Order From Sup. of Doc, U.S. Government Printing Office Washington. D.C. 20402. SD Cat. No. CI}

Q Order !• rom National Technical Information Service (NTIS)

Springfield, Virginia 22151

19. SECURITY CLASS

(THIS REPORT)

UNCL ASSIFIED

21. NO. OF PAGES

26

20. SECURITY CLASS

(THIS PAGE)

UNCLASSIFIED

22. Price

USCOMM-DC 29042-P74