Printup, Dan

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Journal of the Arkansas Academy of Science Volume 23 Article 7 1969 Experiments in Aerial Photography Dan Printup Arkansas Archeological Survey Follow this and additional works at: https://scholarworks.uark.edu/jaas  Part of the Archaeological Anthropology Commons Recommended Citation Printup, Dan (1969) "Experiments in Aerial Photography," Journal of the Arkansas Academy of Science: Vol. 23 , Article 7. Available at: https://scholarworks.uark.edu/jaas/vol23/iss1/7 This article is available for use under the Creative Commons license: Attribution-NoDerivatives 4.0 International (CC BY-ND 4.0). Users are able to read, download, copy, print, distribute, search, link to the full texts of these articles, or use them for any other lawful purpose, without asking prior permission from the publisher or the author. This Article is brought to you for free and open access by ScholarWorks@UARK. It has been accepted for inclusion in Journal of the Arkansas Academy of Science by an authorized editor of ScholarWorks@UARK. For more information, please contact scholar@uark.edu. 24Arkansas Academy of Science Proceedings, Vol. 23, 1969EXPERIMENTS IN AERIAL PHOTOGRAPHYDan PrintupArkansas Archeological Survey, Fayetteville, ArkansasIn recent years ancient roads, walled areas, architecturalfeatures, long forgotten works of man, have been discovered, oftenaccidentally, as a result of aerial reconnaissance. Improved equip-ment, aircraft, cameras, and materials have made itpossible to photo-graph these areas and produce valuable prints for laboratory analy-sis. Dr. W. B. McCoy, Department of Civil Engineering, Universityof Saskatchewan, in a paper presented at the Sixth Annual Saskatche-wan Archaeological Society Meeting, offered several suggestions forthe use of aerial photography in archeology (1968). He particularlymentioned the work at Louisbourg, an 18th century French fortresson Cape Breton Island. The site is being restored by the CanadianGovernment as a National Park, and aerial photographs were usedin delineating and exploring the fortress area (McCoy 1968).The value of aerial photography to archeological research hasbeen recognized for some time, but the cost of equipment andtrained personnel has limited its use by those with small resourcesof money and equipment. Some excellent work has been done by afew, but the obstacles have discouraged too many of us. In the earlysummer of 1968 an opportunity arose for some experiments of thisnature in connection with archeological work being done in north-west Arkansas in the Ozark Reservoir, under a cooperative agree-ment between the University of Arkansas Museum and the NationalPark Service, Southeast Region (Hoffman 1968).In the latter part of May and early June, 1968, two aerialflights were arranged by the University of Arkansas Museum forthe purpose of photographing certain archeological sites in theOzark Reservoir. Itwas hoped that the resulting photographs wouldreveal additional information that would supplement that alreadyobtained during surface investigations of these sites (Hoffman 1965).Iagreed to handle the photographic chores, although my previousexperience in aerial photography had been limited to making a fewcolor slides of sites on which Ihad worked. These slides were usedto show the general lay of the land and appearance of the areas, andnot for analysis of details of the sites.24Journal of the Arkansas Academy of Science, Vol. 23 [1969], Art. 7Published by Arkansas Academy of Science, 196925Experiments in Aerial PhotographyAIRCRAFTThe aircraft used on both flights in 1968 was a high wing,single engine Aero Commander. The door on the right (the photogra-pher's side) was removed to give an unobstructed view and to avoidreflections. This necessitated sitting far enough back from the open-ing to prevent prop-wash hitting the camera. Itgoes without sayingthat the cameras were secured by straps. A seat belt gave thephotographer a small feeling of security.CAMERAS AND FILMThe cameras used were a Retina III, with a 50mm. f:1.9Schneider lens, and a Contaflex I, with a 45mm. f:2.8 Zeiss Tessarlens. The films used were Kodachrome II,Plus-X Pan, and KodakInfrared. A skylight filter was used with the Plus-X film, and aNo. 25(A) with the IR 135 (infrared).Subjects of the same visual appearance may be quite differentin the amount of infrared radiation that they emit. Infrared filmused without a filter will produce only "ordinary" results. To getthe desired infrared effect, it is necessary to use a filter over thelens (or the light source) in order to eliminate the blue light towhich the film is also sensitive. In the case of the red filter usedwith the infrared film the exposure time is increased considerably.Visual and infrared rays do not focus in the same plane. Unless thecamera has a setting for infrared it is usually necessary to compen-sate for this difference. From the distance at which we were workingin the Ozark Reservoir, with relatively short focus lenses, this wasno problem. The camera was set on infinity, and the results weregood.EXPOSURESSince the sites to be photographed were in cultivated bottomlandalong the Mulberry River, with no elevations that might be delineatedby shadows, both flights were made toward the middle of the day.At the time of the first flight the weather was clear, and soil con-ditions were good, although there was some water standing in thefields. Too much water results in a loss of visible detail on groundsurfaces, and completely arid conditions are even worse. Differencesin soil colors (often significant in archeological work) are mostvisible when the ground has been wet and has partially dried. Thisis particularly true when one is checking old stream channels fromthe air. The old stream beds are quite visible when they are still25Journal of the Arkansas Academy of Science, Vol. 23 [1969], Art. 7https://scholarworks.uark.edu/jaas/vol23/iss1/726Arkansas Academy of Science Proceedingsmoist and the higher areas bordering them have dried out. Theyare best seen, of course, on relatively level cultivated land.On the first flight Kodachrome IIwas used in the Retina.Exposures were at 1/250 second at f:5.6; one stop smaller wouldhave given better exposures. The built-in exposure meter could notbe relied upon, as the slight bumping of the plane caused too muchfluctuation of the indicator needle.Plus-X film was used in the Contaflex on the flight. Goodexposures were obtained at 1/500 second at f:8, with the skylightfilter.The weather was partly cloudy at the time of the second flight,but the site areas were clear for the first part of the flight. Onthis flight Plus-X film was used in the Retina, with a skylightfilter, and IR 135 (infrared) in the Contaflex with the No. 25 filter.In the publication Kodak Black and White Films in Rolls(Eastman Kodak Company 1967), the manufacturers explain that,since photoelectric cells measure only visible light and this mayvary considerably from infrared radiation from the same area, it isimpossible to give exact data for exposing infrared film. On thebasis of a suggested trial exposure our infrared pictures were takenat 1/250 second at f:2.8, using the No. 25 filter. (The advantage ofusing a fine lens such as the Zeiss Tessar is that it willgive excellentdefinition at full aperture.) Our results were very good.All shots were necessarily oblique because they were madethrough the plane door, with the camera held inside the plane. Al-titudes were between 200 and 500 feet.RESULTSThe results of our aerial photography were rewarding (Hoff-man 1968: 10), the infrared film brought out some elements thatwere not picked up by the Plus-X film. This was particularly trueat the Spinach Patch Site (3FR1) where the infrared pictures sug-gested there may have been a second mound in addition to the onealready recognized on the surface and from Plus-X photographs madeduring the first flight (Hoffman 1968: 3). What looked like a'eatureless sandy area when we flew over the Natural Levee Site(3FR33) showed some soil discolorations in the Plus-X pictures.These discolorations were much more noticeable in the infraredphotographs. The aerial photographs suggested that the River BankSite (3FR23) extended into an area that had not been recognized26Journal of the Arkansas Academy of Science, Vol. 23 [1969], Art. 7Published by Arkansas Academy of Science, 196927Experiments in Aerial Photographyduring surface investigations. This has since been confirmed bysurface examination.At the Spinach Patch Site the soil was drier at the time ofthe second flight (when infrared film was used), and this usuallyresults in a loss of detail. Even so, the infrared photographs showedmore detail than did the Plus-X pictures made under more moistconditions. Itis possible, of course, by manipulations during print-ing to produce pictures from the same negative that look quitedifferent from each other. In processing the film from these flightsand printing the pictures every effort was made to get "normal"prints with no exaggeration of any aspect.SUGGESTIONSAlthough we were pleased with the results of our first aerialreconnaissance, there are several points that deserve considerationbefore additional flights are made:(1) If possible, flights for aerial photographic purposes shouldbe made on clear days. Although haze penetration is one of thequalities of infrared film, ground shadows cast by clouds were quitedark in prints. This would seem to indicate that the cloud coverhad obstructed the infrared as well as the visual rays.(2) Unless the photographer and pilot are familiar with thearea being photographed, it would be helpful to have ground markersdelineating the area of interest. Strips of white cloth of knownlength would give scale as well as location.(3) While a 50mm. lens with an angle of approximately 46degrees does well enough in showing a large site, it necessitatesflying too low in order to get a large image of a small area. Most ofour pictures were made at around 400 feet altitude; an effort to geta larger image at the Spinach Patch Site from about 200 feet wasunsuccessful.Using a 45mm. lens from about 400 feet altitude we got goodover-all pictures of the Spinach Patch Site and adjacent areas. Hadwe then switched to a 135mm. lens we could have made detailedpictures of specific areas. These would have been more useful inanalyzing the site.(4) Excellent sketch maps can be made from aerial photo-graphs, but detailed measurements arc probably beyond the rangeof our equipment.27Journal of the Arkansas Academy of Science, Vol. 23 [1969], Art. 7https://scholarworks.uark.edu/jaas/vol23/iss1/728Arkansas Academy of Science Proceedings(4) Another factor is safety. With lenses of suitable focallength there is no need to fly dangerously low.The cameras that we have described are not ideal for aerialwork. We have determined, however, that it is possible to do usefulaerial reconnaissance without special equipment. The 135mm. lensmight seem to be special, but anyone doing serious photographicwork should have lenses of different focal lengths. The skylightfilter is standard with many photographers who keep it on camerasin which ordinary film is used. It protects the lens and does notalter exposure requirements. The No. 25 filter is not an expensiveitem.Obtaining the use of a plane is a bit more of a problem. Allsimilar flights that Ihave made prior to the Ozark Reservoir havebeen in a plane owned by a friend who was interested in what wewere doing. Iknow of several others who are sufficiently inter-ested in the archeological work being done in their areas to con-tribute the use of their personal aircraft. Local flying schools wouldseems a good place to start trying to locate such persons.Having discovered the possibility of doing relatively inex-pensive aerial reconnaissance, we are hoping to use this archeologicaltool to good advantage during the coming season. We were pleasedwith the results obtained last summer, but additional experience willundoubtedly result in photographs of even greater archeologicalvalue.REFERENCES CITEDEastman Kodak Company1967 Kodak Black avd White Films inRolls, Third Edition.Kodak Photo Information Book, Advanced AF/1S.Rochester.Hoffman, Michael P.1965 An Archeological Survey of the Ozark Reservoir inWest-Central Arkansas. Manuscript on deposit at theSoutheast Archeological Center, Macon, and the Uni-versity of Arkansas Museum, Fayetteville.1968 Aerial Photography over Ozark Reservoir in West-Central Arkansas. Manuscript on deposit at the South-east Archeological Center, Macon, and the Universityof Arkansas Museum, Fayetteville.McCoy, W. B.1968 Photography in Archeology. Saskatchewan ArcheologyNewsletter, No. 22, pp. 7-11. Regina.28Journal of the Arkansas Academy of Science, Vol. 23 [1969], Art. 7Published by Arkansas Academy of Science, 1969

Experiments in Aerial Photography

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Journal of the Arkansas Academy of ScienceVolume 23 Article 71969Experiments in Aerial PhotographyDan PrintupArkansas Archeological SurveyFollow this and additional works at: http://scholarworks.uark.edu/jaasPart of the Archaeological Anthropology CommonsThis article is available for use under the Creative Commons license: Attribution-NoDerivatives 4.0 International (CC BY-ND 4.0). Users are able toread, download, copy, print, distribute, search, link to the full texts of these articles, or use them for any other lawful purpose, without asking priorpermission from the publisher or the author.This Article is brought to you for free and open access by ScholarWorks@UARK. It has been accepted for inclusion in Journal of the Arkansas Academyof Science by an authorized editor of ScholarWorks@UARK. For more information, please contact scholar@uark.edu, ccmiddle@uark.edu.Recommended CitationPrintup, Dan (1969) "Experiments in Aerial Photography," Journal of the Arkansas Academy of Science: Vol. 23 , Article 7.Available at: http://scholarworks.uark.edu/jaas/vol23/iss1/724Arkansas Academy of Science Proceedings, Vol. 23, 1969EXPERIMENTS IN AERIAL PHOTOGRAPHYDan PrintupArkansas Archeological Survey, Fayetteville, ArkansasIn recent years ancient roads, walled areas, architecturalfeatures, long forgotten works of man, have been discovered, oftenaccidentally, as a result of aerial reconnaissance. Improved equip-ment, aircraft, cameras, and materials have made itpossible to photo-graph these areas and produce valuable prints for laboratory analy-sis. Dr. W. B. McCoy, Department of Civil Engineering, Universityof Saskatchewan, in a paper presented at the Sixth Annual Saskatche-wan Archaeological Society Meeting, offered several suggestions forthe use of aerial photography in archeology (1968). He particularlymentioned the work at Louisbourg, an 18th century French fortresson Cape Breton Island. The site is being restored by the CanadianGovernment as a National Park, and aerial photographs were usedin delineating and exploring the fortress area (McCoy 1968).The value of aerial photography to archeological research hasbeen recognized for some time, but the cost of equipment andtrained personnel has limited its use by those with small resourcesof money and equipment. Some excellent work has been done by afew, but the obstacles have discouraged too many of us. In the earlysummer of 1968 an opportunity arose for some experiments of thisnature in connection with archeological work being done in north-west Arkansas in the Ozark Reservoir, under a cooperative agree-ment between the University of Arkansas Museum and the NationalPark Service, Southeast Region (Hoffman 1968).In the latter part of May and early June, 1968, two aerialflights were arranged by the University of Arkansas Museum forthe purpose of photographing certain archeological sites in theOzark Reservoir. Itwas hoped that the resulting photographs wouldreveal additional information that would supplement that alreadyobtained during surface investigations of these sites (Hoffman 1965).Iagreed to handle the photographic chores, although my previousexperience in aerial photography had been limited to making a fewcolor slides of sites on which Ihad worked. These slides were usedto show the general lay of the land and appearance of the areas, andnot for analysis of details of the sites.24Journal of the Arkansas Academy of Science, Vol. 23 [1969], Art. 7Published by Arkansas Academy of Science, 196925Experiments in Aerial PhotographyAIRCRAFTThe aircraft used on both flights in 1968 was a high wing,single engine Aero Commander. The door on the right (the photogra-pher's side) was removed to give an unobstructed view and to avoidreflections. This necessitated sitting far enough back from the open-ing to prevent prop-wash hitting the camera. Itgoes without sayingthat the cameras were secured by straps. A seat belt gave thephotographer a small feeling of security.CAMERAS AND FILMThe cameras used were a Retina III, with a 50mm. f:1.9Schneider lens, and a Contaflex I, with a 45mm. f:2.8 Zeiss Tessarlens. The films used were Kodachrome II,Plus-X Pan, and KodakInfrared. A skylight filter was used with the Plus-X film, and aNo. 25(A) with the IR 135 (infrared).Subjects of the same visual appearance may be quite differentin the amount of infrared radiation that they emit. Infrared filmused without a filter will produce only "ordinary" results. To getthe desired infrared effect, it is necessary to use a filter over thelens (or the light source) in order to eliminate the blue light towhich the film is also sensitive. In the case of the red filter usedwith the infrared film the exposure time is increased considerably.Visual and infrared rays do not focus in the same plane. Unless thecamera has a setting for infrared it is usually necessary to compen-sate for this difference. From the distance at which we were workingin the Ozark Reservoir, with relatively short focus lenses, this wasno problem. The camera was set on infinity, and the results weregood.EXPOSURESSince the sites to be photographed were in cultivated bottomlandalong the Mulberry River, with no elevations that might be delineatedby shadows, both flights were made toward the middle of the day.At the time of the first flight the weather was clear, and soil con-ditions were good, although there was some water standing in thefields. Too much water results in a loss of visible detail on groundsurfaces, and completely arid conditions are even worse. Differencesin soil colors (often significant in archeological work) are mostvisible when the ground has been wet and has partially dried. Thisis particularly true when one is checking old stream channels fromthe air. The old stream beds are quite visible when they are still25Journal of the Arkansas Academy of Science, Vol. 23 [1969], Art. 7http://scholarworks.uark.edu/jaas/vol23/iss1/726Arkansas Academy of Science Proceedingsmoist and the higher areas bordering them have dried out. Theyare best seen, of course, on relatively level cultivated land.On the first flight Kodachrome IIwas used in the Retina.Exposures were at 1/250 second at f:5.6; one stop smaller wouldhave given better exposures. The built-in exposure meter could notbe relied upon, as the slight bumping of the plane caused too muchfluctuation of the indicator needle.Plus-X film was used in the Contaflex on the flight. Goodexposures were obtained at 1/500 second at f:8, with the skylightfilter.The weather was partly cloudy at the time of the second flight,but the site areas were clear for the first part of the flight. Onthis flight Plus-X film was used in the Retina, with a skylightfilter, and IR 135 (infrared) in the Contaflex with the No. 25 filter.In the publication Kodak Black and White Films in Rolls(Eastman Kodak Company 1967), the manufacturers explain that,since photoelectric cells measure only visible light and this mayvary considerably from infrared radiation from the same area, it isimpossible to give exact data for exposing infrared film. On thebasis of a suggested trial exposure our infrared pictures were takenat 1/250 second at f:2.8, using the No. 25 filter. (The advantage ofusing a fine lens such as the Zeiss Tessar is that it willgive excellentdefinition at full aperture.) Our results were very good.All shots were necessarily oblique because they were madethrough the plane door, with the camera held inside the plane. Al-titudes were between 200 and 500 feet.RESULTSThe results of our aerial photography were rewarding (Hoff-man 1968: 10), the infrared film brought out some elements thatwere not picked up by the Plus-X film. This was particularly trueat the Spinach Patch Site (3FR1) where the infrared pictures sug-gested there may have been a second mound in addition to the onealready recognized on the surface and from Plus-X photographs madeduring the first flight (Hoffman 1968: 3). What looked like a'eatureless sandy area when we flew over the Natural Levee Site(3FR33) showed some soil discolorations in the Plus-X pictures.These discolorations were much more noticeable in the infraredphotographs. The aerial photographs suggested that the River BankSite (3FR23) extended into an area that had not been recognized26Journal of the Arkansas Academy of Science, Vol. 23 [1969], Art. 7Published by Arkansas Academy of Science, 196927Experiments in Aerial Photographyduring surface investigations. This has since been confirmed bysurface examination.At the Spinach Patch Site the soil was drier at the time ofthe second flight (when infrared film was used), and this usuallyresults in a loss of detail. Even so, the infrared photographs showedmore detail than did the Plus-X pictures made under more moistconditions. Itis possible, of course, by manipulations during print-ing to produce pictures from the same negative that look quitedifferent from each other. In processing the film from these flightsand printing the pictures every effort was made to get "normal"prints with no exaggeration of any aspect.SUGGESTIONSAlthough we were pleased with the results of our first aerialreconnaissance, there are several points that deserve considerationbefore additional flights are made:(1) If possible, flights for aerial photographic purposes shouldbe made on clear days. Although haze penetration is one of thequalities of infrared film, ground shadows cast by clouds were quitedark in prints. This would seem to indicate that the cloud coverhad obstructed the infrared as well as the visual rays.(2) Unless the photographer and pilot are familiar with thearea being photographed, it would be helpful to have ground markersdelineating the area of interest. Strips of white cloth of knownlength would give scale as well as location.(3) While a 50mm. lens with an angle of approximately 46degrees does well enough in showing a large site, it necessitatesflying too low in order to get a large image of a small area. Most ofour pictures were made at around 400 feet altitude; an effort to geta larger image at the Spinach Patch Site from about 200 feet wasunsuccessful.Using a 45mm. lens from about 400 feet altitude we got goodover-all pictures of the Spinach Patch Site and adjacent areas. Hadwe then switched to a 135mm. lens we could have made detailedpictures of specific areas. These would have been more useful inanalyzing the site.(4) Excellent sketch maps can be made from aerial photo-graphs, but detailed measurements arc probably beyond the rangeof our equipment.27Journal of the Arkansas Academy of Science, Vol. 23 [1969], Art. 7http://scholarworks.uark.edu/jaas/vol23/iss1/728Arkansas Academy of Science Proceedings(4) Another factor is safety. With lenses of suitable focallength there is no need to fly dangerously low.The cameras that we have described are not ideal for aerialwork. We have determined, however, that it is possible to do usefulaerial reconnaissance without special equipment. The 135mm. lensmight seem to be special, but anyone doing serious photographicwork should have lenses of different focal lengths. The skylightfilter is standard with many photographers who keep it on camerasin which ordinary film is used. It protects the lens and does notalter exposure requirements. The No. 25 filter is not an expensiveitem.Obtaining the use of a plane is a bit more of a problem. Allsimilar flights that Ihave made prior to the Ozark Reservoir havebeen in a plane owned by a friend who was interested in what wewere doing. Iknow of several others who are sufficiently inter-ested in the archeological work being done in their areas to con-tribute the use of their personal aircraft. Local flying schools wouldseems a good place to start trying to locate such persons.Having discovered the possibility of doing relatively inex-pensive aerial reconnaissance, we are hoping to use this archeologicaltool to good advantage during the coming season. We were pleasedwith the results obtained last summer, but additional experience willundoubtedly result in photographs of even greater archeologicalvalue.REFERENCES CITEDEastman Kodak Company1967 Kodak Black avd White Films inRolls, Third Edition.Kodak Photo Information Book, Advanced AF/1S.Rochester.Hoffman, Michael P.1965 An Archeological Survey of the Ozark Reservoir inWest-Central Arkansas. Manuscript on deposit at theSoutheast Archeological Center, Macon, and the Uni-versity of Arkansas Museum, Fayetteville.1968 Aerial Photography over Ozark Reservoir in West-Central Arkansas. Manuscript on deposit at the South-east Archeological Center, Macon, and the Universityof Arkansas Museum, Fayetteville.McCoy, W. B.1968 Photography in Archeology. Saskatchewan ArcheologyNewsletter, No. 22, pp. 7-11. Regina.28Journal of the Arkansas Academy of Science, Vol. 23 [1969], Art. 7Published by Arkansas Academy of Science, 1969

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