1942. Figure 3B. Comparison of aerial photographs of different scales. Type of photograph necessary for forest insect survey work, scale 1:2,500.
Figure 3B. Comparison of aerial photographs of different scales. Type of photograph necessary for forest insect survey work, scale 1:2,500.
See also Figure 3A:
Photo by: F.P. Keen
Publication Date: December 7, 1942; photo date: 1927
This photograph and the following excerpt are from: Eaton, Charles B. December 7, 1942. The Adaptation of Aerial Methods to the Forest Loss Survey. USDA, Bureau of Entomology and Plant Quarantine. Berkeley, California. 24 pages.
"The use of Airplanes in the West
The earliest attempt to survey forest insect damage from the air was made by Miller (1926) in 1925. A photographic and observation plane were supplied by the Army Air Service, and flights were made over the Sierra National Forest. Aerial photographs were taken of the Cascadel and Bass Lake units at an elevation of about 9,000 feet above the average ground level. It was found that individual trees could be distinguished on the photographs, but that it was not always possible to discern the insect-killed trees. A ground check showed that 90 percent of the insect-killed timber, still retaining discolored foliage, registered in the pictures. However the scale of these pictures was really too small to be satisfactory, and without a ground check it would have been impossible to estimate the number of dead trees from the photographs alone.
The following year a test was made of aerial spotting and sample plot photography under eastside conditions. Through arrangements with the Forest Service, ad fores fire patrol contract plane was assigned to the Modoc National Forest for a two-day flight over the Happy Camp-Lava Beds area. Flights were made on September 25 and 28, 1927, with Captain Boggs piloting the plane and Keen (1927) making the observations and taking both vertical and oblique photographs with a 4x5 aerial hand camera from over the side of the open cockpit. Two dozen pictures were taken mostly from an elevation of about 2,000 feet above the forest.
The plan for this experiment as recalled by Keen was two-fold. First, to see what could be done in general reconnaissance by spotting red-top trees on a map and by oblique photographs using panchromatic film and a color filter; and secondly, to test the use of vertical photographs as a sampling method. For this latter test, ground preparations consisted of laying out two 40 acre plots with the corners marked by a flag of newspaper laid on the ground and held down by rocks. On each of the plots all beetle-killed trees, both red-tops and current loss, were tabulated and mapped, so that a comparison could be made between the number identified in the photographs and the number actually on the ground.
On the first day's flight, general reconnaissance methods were tested. With a half-inch to the mile scale map mounted on a drawing board and held in his lap, Keen attempted to job down the number and location of red-top trees as seen ffrom the plane. While a splendid view was had of the forest and the general distribution of infested trees, it soon became apparent that it was impossible to count those trees or spot them on the map. Red-top trees were everywhere - conspicuous when near at hand, but fading into the distance and into the green forest as this stretched off to the horizon. There was no place to begin or end the tree count or to be sure where to spot them on the map. The oblique photographs were of more value, but involved the same difficulties: namely, decreasing visibility in the distance and no line of demarcation for a strip count.
On the second day's flight, the plane was flown over the previously marked 40 acre plots. When directly over the plot, at a signal from Keen, the pilot stalled the plane by pulling up the nose and shutting off the motor. The camera had to be held over and away from the side of the fuselage to avoid vibration. This required unfastening the safety belt and kneeling in the seat with one arm around a guy wire. It did not add to the photographer's comfort when the pilot tipped the plane sideways so that the view directly downward was totally unobstructed.
It had been planned to take verticals at several elevations above the forest so as to determine what scale would take in the 40-acre plots and be of greatest usefulness as photographic samples. However, the plane did not have sufficient power to fly higher than 2,000 feet above the forest, so other flight levels were not flown. At the 2,000 foot level, the 4x5 prints covered a ground area approximately 10 acres which would have been satisfactory for the sampling purposed proved a large series of pictures could have been taken at random over the area. On this scale red-top trees showed plainly when taken with an "A" filter (Figure 3B). For sampling a large area it appeared that verticals taking in a larger ground area would have been more preferable.
This test of pine beetle surveying from the air showed that it had definite possibilities and also limitations. It could be of great value for general reconnaissance of unfamiliar areas, but spotting and counts made by eye were impractical in large areas of unbroken forest. Sampling by vertical photographs was shown to be entirely practical for red top surveys, but that additional tests were needed to work out many details as to most satisfactory flight elevations and maps scale, comparison with ground conditions and relative costs."
See other photos taken during Keen's 1927 flight:
www.flickr.com/photos/151887236@N05/34999650176/in/dateta...
www.flickr.com/photos/151887236@N05/34907772501/in/datepo...
www.flickr.com/photos/151887236@N05/34907767221/in/datepo...
www.flickr.com/photos/151887236@N05/34195868374/in/datepo...
www.flickr.com/photos/151887236@N05/35039958275/in/datepo...
www.flickr.com/photos/151887236@N05/37180017502/in/datepo...
Credit: USDA Forest Service, Region 6, State and Private Forestry, Forest Health Protection.
Source: Aerial Survey Program collection.
Image provided by USDA Forest Service, Pacific Northwest Region, State and Private Forestry, Forest Health Protection: www.fs.usda.gov/main/r6/forest-grasslandhealth
1942. Figure 3B. Comparison of aerial photographs of different scales. Type of photograph necessary for forest insect survey work, scale 1:2,500.
Figure 3B. Comparison of aerial photographs of different scales. Type of photograph necessary for forest insect survey work, scale 1:2,500.
See also Figure 3A:
Photo by: F.P. Keen
Publication Date: December 7, 1942; photo date: 1927
This photograph and the following excerpt are from: Eaton, Charles B. December 7, 1942. The Adaptation of Aerial Methods to the Forest Loss Survey. USDA, Bureau of Entomology and Plant Quarantine. Berkeley, California. 24 pages.
"The use of Airplanes in the West
The earliest attempt to survey forest insect damage from the air was made by Miller (1926) in 1925. A photographic and observation plane were supplied by the Army Air Service, and flights were made over the Sierra National Forest. Aerial photographs were taken of the Cascadel and Bass Lake units at an elevation of about 9,000 feet above the average ground level. It was found that individual trees could be distinguished on the photographs, but that it was not always possible to discern the insect-killed trees. A ground check showed that 90 percent of the insect-killed timber, still retaining discolored foliage, registered in the pictures. However the scale of these pictures was really too small to be satisfactory, and without a ground check it would have been impossible to estimate the number of dead trees from the photographs alone.
The following year a test was made of aerial spotting and sample plot photography under eastside conditions. Through arrangements with the Forest Service, ad fores fire patrol contract plane was assigned to the Modoc National Forest for a two-day flight over the Happy Camp-Lava Beds area. Flights were made on September 25 and 28, 1927, with Captain Boggs piloting the plane and Keen (1927) making the observations and taking both vertical and oblique photographs with a 4x5 aerial hand camera from over the side of the open cockpit. Two dozen pictures were taken mostly from an elevation of about 2,000 feet above the forest.
The plan for this experiment as recalled by Keen was two-fold. First, to see what could be done in general reconnaissance by spotting red-top trees on a map and by oblique photographs using panchromatic film and a color filter; and secondly, to test the use of vertical photographs as a sampling method. For this latter test, ground preparations consisted of laying out two 40 acre plots with the corners marked by a flag of newspaper laid on the ground and held down by rocks. On each of the plots all beetle-killed trees, both red-tops and current loss, were tabulated and mapped, so that a comparison could be made between the number identified in the photographs and the number actually on the ground.
On the first day's flight, general reconnaissance methods were tested. With a half-inch to the mile scale map mounted on a drawing board and held in his lap, Keen attempted to job down the number and location of red-top trees as seen ffrom the plane. While a splendid view was had of the forest and the general distribution of infested trees, it soon became apparent that it was impossible to count those trees or spot them on the map. Red-top trees were everywhere - conspicuous when near at hand, but fading into the distance and into the green forest as this stretched off to the horizon. There was no place to begin or end the tree count or to be sure where to spot them on the map. The oblique photographs were of more value, but involved the same difficulties: namely, decreasing visibility in the distance and no line of demarcation for a strip count.
On the second day's flight, the plane was flown over the previously marked 40 acre plots. When directly over the plot, at a signal from Keen, the pilot stalled the plane by pulling up the nose and shutting off the motor. The camera had to be held over and away from the side of the fuselage to avoid vibration. This required unfastening the safety belt and kneeling in the seat with one arm around a guy wire. It did not add to the photographer's comfort when the pilot tipped the plane sideways so that the view directly downward was totally unobstructed.
It had been planned to take verticals at several elevations above the forest so as to determine what scale would take in the 40-acre plots and be of greatest usefulness as photographic samples. However, the plane did not have sufficient power to fly higher than 2,000 feet above the forest, so other flight levels were not flown. At the 2,000 foot level, the 4x5 prints covered a ground area approximately 10 acres which would have been satisfactory for the sampling purposed proved a large series of pictures could have been taken at random over the area. On this scale red-top trees showed plainly when taken with an "A" filter (Figure 3B). For sampling a large area it appeared that verticals taking in a larger ground area would have been more preferable.
This test of pine beetle surveying from the air showed that it had definite possibilities and also limitations. It could be of great value for general reconnaissance of unfamiliar areas, but spotting and counts made by eye were impractical in large areas of unbroken forest. Sampling by vertical photographs was shown to be entirely practical for red top surveys, but that additional tests were needed to work out many details as to most satisfactory flight elevations and maps scale, comparison with ground conditions and relative costs."
See other photos taken during Keen's 1927 flight:
www.flickr.com/photos/151887236@N05/34999650176/in/dateta...
www.flickr.com/photos/151887236@N05/34907772501/in/datepo...
www.flickr.com/photos/151887236@N05/34907767221/in/datepo...
www.flickr.com/photos/151887236@N05/34195868374/in/datepo...
www.flickr.com/photos/151887236@N05/35039958275/in/datepo...
www.flickr.com/photos/151887236@N05/37180017502/in/datepo...
Credit: USDA Forest Service, Region 6, State and Private Forestry, Forest Health Protection.
Source: Aerial Survey Program collection.
Image provided by USDA Forest Service, Pacific Northwest Region, State and Private Forestry, Forest Health Protection: www.fs.usda.gov/main/r6/forest-grasslandhealth