FIG. 1. Black and white photograph of a portion of the test area near Bennettsville, South Carolina. The original scale was 1:20,000-this reproduction is about 1:32,000. See also Figure 5.

ABRAHAM ANSON* U. S. Army Engineer GIMRADA Fort Belvoir, Virginia

Color Photo Comparison

A photo interpretation test with Panchromatic, Color, and Ektachrome IR establishes the superiority of the latter two for mapping drainage, vegetation, soils and culture.

(Abstract on page 289)

INTRODUCTION Bennettsville, South Carolina, Test Area. The test was designed to obtain quantitative and DIHECT HESULT of the action by the mem­ qualitative information regarding the role of bers of the Color Photography Commit­ A color, infrared and special purpose films in tee of the American Society of Photogram­ photogrammetric applications. The purpose metry was a series of test flights over the of this paper is to report on a comparative photointerpretation study of a controlled * Presented at the Semi Annual Convention of test area, photographed in black and white the American Society of Photogrammetry at panchromatic, color, and Kodak Ektachrome Dayton, Ohio, September 1965, see under the title "Comparative Photointerpretation from Panchro­ Infrared Aero Film Process E-3, also known matic, Color, and Ektachrome IR Photography." as false-color film. Each emulsion was exposed

*»-+ FIG. 2. Aero Ektachrome color photograph of approximately the same area as shown in Figure 1.

FIG. 3. Anscochrome aerial color photograph of approximately the same area shown in Figures 1 and 2.

FIG. 4. Aero Ektachrome IR photograph (sometimes referred to as CD-camouflage detection) of approximately the same area as shown in Figures 1, 2, and 3. 286

COLOR PHOTO COMPARISON 289 under essen tiall y iden tical conditions, regard­ in order to utilize any valid information re­ ing camera, vehicle, and personnel over the garding the comparative characteristics of same target area. each emulsion from the available photog­ Arrangements for the flight by the U. S. raphy. Upon re-examination of the photog­ Air Force were made by the Defense Intel­ raphy, the several organizations of \-Vorking ligence Agency. The test \I'as conducted under Group I, which met at Army Map Service, the guidance of the Coast and Geodetic relinquished all tasks except photoidentifica­ Survey, over an area specified by the Color tion and photointerpretation, undertaken by Photography Committee of the American GIMRADA, with the assistance of the Army Society of Photogrammetry. Field engineers Map Service. During this period, the Itek provided by the Army Map Service were Corporation, Data Analysis Center, Alex­ available to obtain ground identification in­ andria, Virginia, offered the services of its formation. personnel for photointerpretation under a The aerial photography obtained over a Loan Agreement with GIMRADA. This re-

ABSTRACT: As the result of action by the Color Photography Committee of the A merican Society of Photogrammetry, panchromatic, color and Ektackrome IR photography of the same area were compared under essentially identical conditions. The study includes the identification and interpretation of drainage, vegetation, soils, and map features such as roads, railroads, and buildings. As a control the same features were identified on the ground. In addition, the photointerpretors were required to identify 42 selected photopoints that appeared photographs. On the basis of tile limited study, Ektachrome IR photography proved to be superior to color and to panchromatic photograplly for mapping, vegetation, and drainage. Color photography was found to be superior to pan­ chromatic and Ektachrome I Rfor mapping soils and culture.

three week period was flown at 2,500, 10,000, port will be concerned principally \\'ith the 20,000 and 30,000 feet above terrain. results of their study and an evaluation by After processing by the Coast and Geo­ the author and other GIMRADA personnel. detic Survey, it was apparen t that not all of Cooperating agencies in this effort include the photography produced was acceptable for the U. S. Air Force; the Coast & Geodetic the following reasons: Survey; the Eastman Kodak Company; the Ansco Corporation; the Fairchild Camera and * The fligh ts were made over a period of several weeks. The length of ti me in vol ved Instrument Corporation; the U. S. Army Map included unavoidable changes in weather Service; the Itek Corporation; and the U. S. which had some effect upon the resulting Army Engineer Geodesy, Intelligence and photography. Mapping Research and Development Agency. * An exposure developmen t test could INVESTlGATION not be made prior to the completion of the photography. An RC-130 Aircraft, furnished by the U. S. * Atmospheric haze affected color fidel­ Air Force, was used as the camera vehicle. ity as well as the black and white photog­ Fairchild Camera and Instrument Cor­ poration supplied a six-inch focal length KC-4 raphy at the test si teo The camera window tint of the vehicle Camera, 9X9 inch format, equipped with a * Geocon, color corrected lens, from which the used, in association with the color COiTec­ tion characteristics of the cameras, pro­ panchromatic photography used in this analysis was obtained. The Coast and Geo­ vided a color bias in the resulting aerial photography. detic Survey supplied a Wild RC-8 Camera 9X9 inch format, equipped with a six inch GI 1RADA personnel suggested that the focal length, Aviogon lens, color corrected, flights at 10,000 feet had sufficient informa­ \I'ith an anti-vignetting filter for obtaining tion in all three emulsions to justify detailed color and Ektachrome Infrared aerial photog­ analysis. Working Group I was formed at the raphy. Color Photography meeting in October, 1964, The Ansco Corporation supplied Plestar 290 PHOTOGRAMMETRIC ENGINEERING

FIG. 5. Mosaic of black and white photographs of the test area showing Bennettsville, South Caroli na at a scale of approximately 1: 64,000. base, Anscochrome Aerial film, a color re­ to obtain the following detailed information versal film in 9! inch widths. The Eastman in each of the 42 selected ground control Kodak Company supplied Ektachrome MS poin ts: Aerial Film, a color reversal film, on an Estar 1. Vegetation. base; Ektachrome Infrared Aerial film on an a. Tree height acetate base; and Kodak PI us X Aerial film, b. Trunk size panchromatic, on an Estar base. Figure 1 c. Tree spacing represents black and white panchromatic pho­ d. General species tography from a flight height of 10,000 feet. e. Ground cover Figure 2 represents Aero Ektachrome, Figure 2. Type of soil (gravel, sand, rock, clay, 3 represents Anscochrome, and Figure 4 rep­ sil t, and mixtures). resents Aero Ektachrome IR photography. 3. Moisture Content. The selection of the Bennettsville Test Area a. Dry was dictated by the following considerations: b. Wet * The U. S. Air Force indicated that the c. Marsh scheduling required the use of an East Coast d. Flooded Test Site if the flights were to be made in 4. Surface Drainage. FY 1964. * The Army Map Service engineers In cultivated areas, crop identification was would be available in the area to obtain the requested; in populated areas, the type of ground truth necessary for control of photo­ structure was also requested. interpretation procedures. A detailed operational plan was prepared by the author for the photointerpretation In addition to an overall interpretation of work to be performed by the I tek Corpora­ the Test Site, which is approximately 30 tion. In order to eliminate the bias which square miles (Figure 5), interpretation was could occur from a direct comparison of the required for 42 photo points selected to ob­ three emulsions, the interpreters were given tain more precise ground information (Figure one set of photographs at a time in stereo 6). The AMS field engineers were requested coverage with a small scale general map of the

Q". a.. 0... 0.... 0 .. Q" Q", G., 0 .... 0'" 0 •• 0 .., 0·"a... O~" O~.. 0 .•. 0 ... Qm O~" 0.". 0., 0 ... 0... 0" .. Q" 0.,,·

0,,,. L

FIG. 6. Descriptive points and ground stations in test area shown in Figure 5. COLOR PHOTO COMPARISON 291

FIG. 7. Drainage map compiled from black and white photography of test area shown in Figures 5 and 6. Compare with Figures 8 and 9. area and a text, "Geology of the Coastal photomosaic. During this period the AlVIS Plain of South Carolina," a report by the field engineers were obtaining the ground U. S. Geological Survey, published in 1933. truth. The instnlctions to the interpreters for each Zeiss mirror stereoscopes with six power set of photographs were as follows: magnification were used for the Photo inter­ pretation; Stereometers were used for making • Prepare a drainage map at photo scale, elevation measuremen ts. The two in terpreters 1: 20,000, incl uding, primary, secondary, and tertiary drainage, used in this task were skilled in mapmaking and field geologic investigation procedures. • Prepare a vegetation map at photo scale, differentiating the species within ob­ servable capabilities, STUDY RES LTS • Prepare a soils map at photoscale for Rather than a direct comparison of the in­ identification of similar soils areas, with a formation content or interpretability of the key for each area, and, three types of photography; the photointer­ • Prepare a cuI ture map at photo scale, pretation procedures resulted in the prepara­ identifying roads, railroads and special tion of three independent studies and no dis­ purpose buildings. tinction was made between the Anscochrome The interpreters were not given the ground and Ektachrome films. The following is an truth, they could not compare one set of account of the interpreters findings. photos wi th the other two, nor could they use the small scale map as a reference. In DRAINAGE addi tion to the required maps, they were re­ A visual comparison of the overlays shows quested to make an analysis of the 42 selected an increasing amount of drainage density photo points, and required to supply the mapped from panchromatic (Figure 7), color identical information that was being procured (Figure 8) and Ektachrome IR photography in the field. (Figure 9), mapped in that order. In the Over a period of six months, the same two interpreter's opinion, the Ektachrome JR interpreters made all of the required interpre­ photography affords a rapid and accurate tations. Upon completion, the Itek Corp. means of mapping drainage. Streams and furnished a report which included a detailed bodies of water appear dark brown to black; analysis of each of the 42 selected photo muddy water around various excavations points with a separate list of items for the appears bluish in tone because of the re­ panchromatic photography, an addendum for flectivity of the sediment. Tertiary and inter­ the color photography and an addendum for mittent drainage lines are readily observed the Ektachrome Infrared photography. Thir­ because of their darker tones, which contrast teen 1: 20,000 scale planimetric maps were with the surrounding areas. The higher mois­ furnished for the comparison. They included ture content of intermittent streambeds a drainage map, a soils map, a vegetation even though dry show a dark image. The con­ map; and a culture map for each emulsion; a fidence level for drainage interpretation is separate map was prepared locating each of highest on the Ektachrome JR photography. the 42 photo points; as well as 1:20,000 scale Compare ponds in Figures 1, 2, 3 and 4. 292 PHOTOGRAMMETRIC ENGINEERING

FIG. 8. Drainage map compiled from color photography. Compare with Figures 7 and 9.

VEGETATION only to this region and for this season of the The two vegetation maps compiled from year. panchromatic (Figure 10) and color photog­ SOILS raphy (Figure 11) indicate almo t the same information densi ty; the Ektachrome IR (Reference Figures 13, 14, and 15). A com­ photography (Figure 12) ho\\'e\'er, shOll'S al­ prehensive soils study \I'as not attempted, most twice the detail that can be in tel' preted since a field trip would have been necessary. from the other two emulsions, The ability of HOlI'el'er, the soils were mapped under the the photointerpreters to determine the den­ premise that similar soils appear in similar sity of \'egetatil'e groll,th appeared to be equal tones and patterns. Approximately the same for all types of photography, but their ability density of soil information was mapped from to extract vegetative detail was far greater on each type of photography. Ektachrome IR photography, since the decid­ uous trees, crops and grasslands show a pre­ GEOLOGY dominantly red tone, whereas the coniferous No geologic structures (folds or faults) or trees which absorbed more infrared appeared rock ou tcrops were observed in any of the in tones of purple. Single trees or small groups three types of photography studied. The of one species standing in an area surrounded major landform of the area is characterized by another species, were easily recognized. by low relief, slightly hummocky, and the An outstanding feature of the IR film was the surface topography is probably deeply under­ ease with which cultivated and fallow crop­ lain by unconsolidated sand and gravel land could be mapped; while two classes of (typical Atlantic Coastal Plain) as evidenced cropland could be determined from the by numerous excavations and pits throughout panchromatic and color photography, four the area. Many Carolina Bay type of depres­ classes could be mapped from the Ektachrome sions with accompanying sand ridges were lIZ photography. These results are applicable observed throughou t the project area.

~ FIG. 9. Drainage map compiled from Ektachrome IR photography. Compare with Figures 7 and 8. COLOR PHOTO COMPARISON 293

k- FIG. 10. Vegetation map compiled from black and white photography of test area shown in Figure 5. Compare with Figures 11 and 12. Legend: (1) Heavily wooded. (2) Woodland thinned by logging. (3) Cul­ tivated field. (4) Thinned woodland. (5) Cleared FLeld; brush. (6) Fallow field. (7) Grass. (8) Orchard. (9) Marsh. (10) Residential or industrial. (11) Strip mine.

L FIG. 11. Vegetation map compiled from color photography. Compare with Figures 10 and 12.

FIG. 12. Vegetation map compiled from Ektachrome lR photography. Compare with Figures 10 and 11.

CULTURE found working with color or Ektachrome II{ (Reference Figures 16, 17, and 18). Three to be more satisfactory regarding speed and detailed culture maps were completed, in confidence. which roads, railroads and cultural features were shown. In a visual comparison of all SPECIFIC AREAS three maps the same information is apparent in maps compiled from color and Ektachrome Two specific areas in the city of Bennetts­ IR, whereas slightly less information was ville were analyzed in detail on the three types interpreted from panchromatic photography. of photography. For cultural determination, \Vhile the amount of information was not the color photography appeared to be most appreciably greater, the photointerpreters ad vantageous. 294 PHOTOGRAMMETRIC ENGINEERING

L

FIG. 13. Soils map compiled from black and white photography of test area shown in Figure 5. Com­ pare with Figures 14 and 15. Legend (in addition to that indicated in Figure 10): (3a) Early planting. (3b) Late planting. (3c) Possibly fallow.

FIG. 14. Soils map compiled from color photography. Compare with Figures 13 and 15.

FIG. 15. Soils map compiled from Ektachrome lR photography. Compare with Figures 13 and 14.

PHOTO POI)./T lDENTll'ICATlON DISCUSSION Each of the 42 pre-selected photo-points The detailed specifications which had been were studied by the interpreters and an at­ prepared by the Color Photography Com­ tempt was made to list the specific items re­ mi ttee of the A merican Society of Photo­ quested of the field engineers. Figure 6 shows gram metry cou.ld no! be implemented as the distribution of the 42 photo points. Table planned. Since so many operations were scat­ J lists the items of information requested tered abou t through several agencies, coordi­ along with the number and correctness of re­ nation became the principal problem. As sponse by the interpreters. mentioned in the beginning of this paper, the COLOR PHOTO COMPARISON 295

FIG. 16. Culture map compiled from black and white photography of test area shown in Figure 5. Compare with Figures 17 and 18.

FIG. 17. Culture map compiled from color photography. Compare with Figures 16 and 18.

FIG. Ill. Culture map compiled from Ektachrome IR photography. Compare with Figures 16 and 17.

U. S. Air Force furnished the vehicle and ground, with their full support in obtaining crew for exposing the aerial photography, ground truth, yet several months elapsed be­ however, it was not possible to fly over the tween exposing the photography on 8-22 pre-selected test area within the time sched­ June 1964 and obtaining ground information uled. The Coast and Geodetic Survey fur­ from October to December, 1964. nished technical advice and photographic Color fidelity was one key to the entire assistance as well as processing facilities, yet project, and the color bias, which appeared as circumstances did not permit exposure de­ an overall green tone in one color emulsion velopment tests, which are considered essen­ and as an overall bl ue tone in another type of tial for this type of mission. No standard color emulsion, led some agencies to withdraw from panels were emplaced in the field. The Army the evaluation procedures. This author is of Map Service field engineers were on the the opinion that the color fidelity i& not as 296 PHOTOGRAMMETRIC ENGINEERING

TABLE I TOTAL 'UMBER OF lTEMS-237

Panchromatic Color Ektachrome IR Field

Correct Response 136 163 165 237 1ncorrect Response 69 47 45 Not Answered 32 27 27

Ratio Correct/Total"limber 136/237 163/237 165/237 Ra tio Incorrect/Correct 69/136 47/163 45/165 Ratio Not Answered/Correct 32/136 27/163 27/163 Ratio Not Answered/Total 32/237 27/237 27/237 much a consideration in photointerpretation selection of detail from the IRand color as color differentiation. This is substantiated photography than from the panchromatic by the results obtained using Ektachrome IR black and white photography, although the Photography, which is a color distortion amount of detail is not significantly greater. medium. To be more specific, if a building, a The numerical analysis of the specific items field tone, or a geological formation differs requested in the 42 selected photo prints was in hue from its surround, then it has its own obtained by totalling all of the individual characteristics and facilitates its identifica­ items requested from the field engineers and tion. It was on this basis that GI IIRADA cross checking this information with the same undertook the photoidentification and photo­ requests made of the photointerpreters. The interpretation task, which \I'as the only correct responses for color were approxi­ evaluation procedure performed by \Vorking mately 20 per cent greater than panchromatic Group 1. It must be stressed, however, that black and white, and 22 per cent greater for the exact nature of the color distortion, if IR film. Conversely there were fewer errors any, should be known. for color photography than for items ex­ In checking the work of the photointer­ tracted from black and white photography. preters, furnished by the Itek Corporation The error ratio was also less for IR photog­ Data Analysis Center, a detailed comparison raphy. Items not determined which included was made of the planimetric maps which were tree trunk size, tree spacing and depth of compiled. The comparison indicated that the ditches were approximately equal for all three color IR Photography reveal much more drain­ emulsions. age information than can be obtained from panchromatic black and white photography. COKCLUSIONS Differences between the information supplied On the basis of the limited study described by either color or IR film are not as great. above, the photointerpreters drew the follow­ The confidence level for drainage determina­ ing conclusions. tion is highest in the IR transparencies, with Ektachrome IR photography is superior to color and panchromatic following in that color and panchromatic photography for the order. mapping of drainage and vegetation. vVith regard to the vegetation analysis, an Color photography is su perior to panchro­ overlay comparison of all three planimetric matic and Ektachrome IR for the purpose of maps displays the superiority of IR film over mapping culture and soils. color or panchromatic film for the classification Pancht'omatic photography is inferior to of vegetation. The spectral response of the Ektachrome IR and color photography in coniferous trees vs deciduous trees as \I'ell as each of the several categories studied. The young crops vs bare ground show a greater interpreters believe that they were unable to contrast in Ektachrome IR Film than in the draw any concrete conclusions from the study other mediu ms. Comparison of the three soils because the quality of the photographs sup­ maps is not conclusive since the photointer­ plied was not the best, the ground truth \I'as preters need field information to make a valid not available to them and they were requested specific analysis. The data derived are rela­ that all three sets of photographs not be tive. visually compared. This experiment has con­ In the mapping of cultural features, the sisted of a comparison study of a small typical photointerpreters have more confidence in the area carried out with photography obtained COLOIZ PHOTO COMPARISON 297 under less than ideal conditions, less than ACKNOWLEDGEMENTS adequately controlled, and compounded by Acknowledgement is made to the following inferior quality materials. The interpreters for assistance in preparing this report: suggest that the information gleaned from Mrs. Clarice Norton, Fairchild Camera and this study be used as a reference for planning Instrument Corporation, Chairman, ASP fu ture studies, and not as conclusive evidence Color Photography Committee. that anyone of the three types of photography Mr. William D. Harris C&GS, Deputy is superior in performance in anyone of the Chairman, Color Photography Commit­ categories studied. The interpreters were not tee. fully aware, because of the test procedures, of Mr. John T. Smith, Jr., C&GS, Consultant the success which accompanied their inter­ in Aerial Photography and Processing. pretations. Mr. Barry Shelkin, Itek Corporation. Working Group I Members RECOMMENDATIONS MI'. James P. Webb, Chairman, AMS The investigators recommend that con­ Mr. Paul H. Alban, AMS sideration be given to controlled sensitometry Mr. S. W. Dossi, AMS for exposure prior to acquisition of the photo­ Mr. J. W. Elliott, USFS graphs and to testing and controlling the Mr. F. W. Masek, AMS. resolution and color response of each type of photography by photographing resolution BIBLIOGRAPHY targets and color panels laid out on the 1. American Soc. Photogrammetry. Manual of ground in the target areas. Photographic Interpretation. The American So­ In order to evaluate fully the merits of the ciety of PhotogramlIletry, 1960. 2. Colwell, Robert N., "Some uses and limitations three types of photography for military, of aerial color photography in agriculture." industrial, agricultural, and geologic inter­ PHOTOGRAMMETIUC ENGINEERING 26: 220-22. pretations, it would be beneficial to obtain 1960. coverage of several different areas, as no one 3. Fisher, William A., "Color aerial photography in geologic investigations." PHOTOGRAMMETRIC area will contain sufficient variety of data to ENGINEERING 28: 133-139. 1962. permi t a complete and detailed study of all 4. Haack, Paul M., "Evaluating color, infrared, possible problems. Ground tru th and geo­ and panchromatic aerial photos for the forest detic control should be compiled and indi­ survey of interior Alaska." PHOTOGRAMMETRfC ENGINEERING 28: 592-98. vid ual targets should be selected to cover the 5. Maruyasu, Takakazu and Nishio, l\~otomitsu. widest range of subjects possible. "Experimental studies on color aenal photo­ The most effective method of study would graphs in Japan." Photograrnrnetria 18: 87-106. be to employ a group of two or more inter­ 1961-62. 6. Ottoson, L. "Comparative tests of the accuracy preters of approximately equal experience and of panchromatic, infrared and color pictures capability who will be allowed to compare from the air for photogramlIletric purposes." visually the three sets of photography with Intern. Congress for Photogrammetry. Stock­ access to all ground tru th and geodetic con­ holm. 1959. 7. Swanson, L. "V. "Photogramll1etric surveys for trol. The interpreters should compile a chart nautical charting use of color and infrared listing terrain and cultural features that can photography." PHOTOGRAMMETRfC ENGINEER­ best be interpreted on each type of photog­ ING 26: 137-41. 1960. raphy, while recording their individual com­ 8. Tarkington, R. G. & Allan L. Sorell1. "Color aJl~ false color films for aerial photography. ments for each feature as the project pro­ PHOTOGRAMMETRIC ENGINEERING 29: 88-95. gresses. 1963.

P aid A dvert-isemc'Ht

AERIAL MAPPING INSTRUMENTS Kelsh Plotters-Multiplexes Ideal for Training and Photogrommetric Studies PACIFIC AIR INDUSTRIES, INC. 725 E. Third Street, long Beach, California SPruce 5-1059 HEmlock 5-8326