The Face of the Earth as Seen from the Air / A Study in the Application of Airplane Photography to Geography

by Willis T. Lee

Engineering Projects Covering Large Areas

Where the project covers large areas, the “mosaic,” or group of matched photographs, can be used in the study of problems of construction or improvement. Figure 13, a mosaic of the Anacostia flats, the site of improvements under way in the District

Fig. 6—The United States Naval Observatory and grounds, Washington, D.C., as seen from an airplane at a height of a few hundred feet above the ground, showing an unusually attractive arrangement of shrubbery and trees.

of Columbia, shows the Anacostia marshes as they appeared in the autumn of 1920, after the changes effected since 1915, as can be seen by comparison with Figure 14, the topographic map of the same area. To the right is the terraced slope rising to a height of about 150 feet above the river—an elevation so low that the air photograph does not properly reproduce it. Near the foot of the principal terrace lie the tracks of the Pennsylvania Railroad, on which can be seen Benning, Deanewood, and Kenilworth. Between the railroad and the Anacostia River are the Benning race track and the swampy lowland and tidal marshes of the Anacostia flats. The river and the marshland on either side of it from the Pennsylvania Avenue Bridge to Benning Road have been modified by dredging, but north of

Fig. 7—Shipyards at Newport News, Va., showing docks and deep-water approaches, steamships, and drydocks, in one of which is a vessel for repairs.

Fig. 8—The New York Connecting Railroad Bridge, which affords an all-rail passenger and freight route between Boston and Washington. The bridge, which was completed in 1917, starts on the mainland in the Port Morris section of southern Bronx Borough, New York City, seen in the background, then crosses Bronx Kill, Randalls Island, Little Hell Gate, Wards Island, and Hell Gate to reach the Long Island shore, seen in the extreme lower right corner, at Long Island City, Queens Borough. The tracks continue towards Washington by way of tunnels under the East River and the Hudson.

Fig. 9—A part of Washington, D.C., showing the White House, Treasury, State-War-Navy, and other public buildings in the foreground; the Ellipse, Washington Monument, and new War and Navy offices in the middle ground; and the Tidal Basin, Potomac Park, and the Potomac River in the distance. By no other means could so informative a glimpse be given of a spot of such wide interest. Every feature in the picture is more or less familiar to a large number of Americans, but their familiarity is with the individual features rather than with their situation and relation to one another as shown here.

Fig. 10—Part of Rockaway Beach, Long Island, N.Y., showing city blocks, streets, and buildings covering the sand which a few years ago was barren and unoccupied. Scale, about 1: 6,700.

Fig. 11—Landscape gardening. An airplane view of a part of Long Branch, N.J., taken from a height of 10,000 feet, showing the beach and surf at the right, and the streets, mansions, driveways, and lawns in the body of the picture—an example of the development of a barrier beach of little value before the exploitation for summer homes. Scale, about 1: 15,000.

this road the surface appears in its natural state. In the mosaic are shown at the left the highlands west of the marshes, wooded in some places but cleared and improved in others. In the northern part can be seen land wooded north of the District line but cleared south of it. So comprehensive a view of the field of the project and of the progress to date should be of great service to the engineers and promoters.

CHAPTER IV
THE MOSAIC
(Figs. 13 and 22)

In its simplest form, the mosaic is made by mounting overlapping prints so that the corresponding details coincide. This type of mosaic is quite adequate for relatively small areas or where a high degree of accuracy is not required. For larger areas and greater accuracy, an accurate outline map is used as a base upon which the prints are mounted so that recognizable features coincide with their location on the map. When the prints are properly arranged, the better print of each overlapping pair is selected, the excess paper removed, and the whole mounted and photographed. Figure 13 is left untrimmed to illustrate the method of matching the overlapping prints. The differences in shade are due to difference in printing and developing the pictures which make up the mosaic. The slight offsetting of line at the junction of the prints may be due to errors in mounting, shrinking, or stretching of the photographic paper, tilting of the camera at the time of exposure, or other cause. Such errors and imperfections illustrate the difficulty of using these photographs in the making of maps.

A skillful manipulation of both airplane and camera is necessary to the success of the mosaic. To prevent distortion and variation of scale, the camera must be maintained at the same altitude at all times and pointed directly downward. This can be accomplished by flying with an even keel at a uniform altitude. Mechanical devices are also being perfected to accomplish the same result. Still greater skill is necessary when consecutive rows of exposures are made for the purpose of placing strips of photographs side by side to cover a large area. It is difficult under the varying conditions of wind and weather to fly so evenly and so nearly at the same level that distortions and differences in scale are not noticeable. Strong objection to the mosaic is frequently raised because of inaccuracies due to difference in scale in neighboring prints. Until these defects are overcome, such a group of matched photographs cannot take the place of an accurate map. Much, however, is being done to correct these defects, and, even in photographs where inaccuracies in scale are many, the value of the photograph for the portrayal of detail cannot be denied.

CHAPTER V
GENERAL ASPECTS OF THE SURFACE AS SEEN FROM THE AIR
(Figs. 12 to 18)

Fig. 12—Benning, D.C., and the Anacostia River, showing, from right to left, cultivated lands 40 to 20 feet above sea level, an elevation too slight to be shown in a vertical photograph; a brushy slope running from 20 feet to sea level; and marshland along the stream. The checkered pattern of the upland fields is caused by different-colored crops. Shocks of corn, spaced evenly in rows, buildings and shade trees, and light-colored roads and a race track are shown. The light-colored areas along the stream are occupied by tidal marsh and are free from brush but covered with vegetation of annual growth. The figure is one of the photographs used to make the mosaic shown on Fig. 13. It should be compared with Fig. 13 and with the topographic map, Fig. 14. Scale, 1: 11,000.

When a region is viewed from an altitude of several thousand feet the observer can readily imagine himself looking down on a large map. The chief features stand out prominently, the smaller to a lesser degree. Mountains, rivers, and the seashore are

Fig. 13—Vertical photograph of the land along the Anacostia River on the eastern edge of Washington, D.C., made up of several photographs matched together and adjusted to points located by ordinary survey methods, and reduced in size to correspond with the map, Fig. 14. The photographs were taken from an airplane with a so-called mapping camera at such intervals of time that the prints overlap, thus making it possible to adjust them to each other and to form a continuous picture of the area. The region shown is the site of improvements that are at present under way, mainly the regulation of the Anacostia River. The channel has been widened by dredging and part of the bordering marsh areas filled in. The photograph shows that this work had progressed to the Benning Road bridge by the autumn of 1920, when the photograph was taken, while in 1915, when the area was surveyed for the map, it had been carried out only as far as the Pennsylvania Avenue bridge. Such airplane photographs furnish an incomparable tool in the handling of large-scale engineering projects, both in the study of the territory in its unimproved state and to follow the progress of the work after operations are under way. Scale, about 1: 28,000.

Fig. 14—Part of the topographic map of Washington and Vicinity, 1: 31,680, published by the U.S. Geological Survey, showing within the irregular line the same area shown in Fig. 13. Scale, 1: 28,000.

Fig. 15 (on page 24)—Mosaic of the southeastern part of Mulberry Island, on the left bank of the James River about 11 miles northwest of Newport News. Va., showing an area portrayed by many photographs matched together. Slight differences in shade indicate the junction of the separate prints. The higher land, about 10 feet above sea level as determined by surveys on the ground, is shown at the right by roads and cultivated fields. It is to be noted that roads outline the dividing line between the high ground and the marsh. At the left are lower areas of wooded or brushy swampland and of grassy marsh. They contain a number of abandoned channels: some completely silted up, others containing small thoroughfares, and still others drained by meandering streams which seem to have developed after the channels were definitely abandoned by the streams which originally occupied them.

The streams which drain the marshes have many characteristics of streams which drain higher lands. They have dendritic patterns, so called from resemblance to the forking branches of a tree; channels which widen downstream; and winding or meandering courses. The island terminates in a long spit composed of silt and fine sand. The banks to the left on James River are low and marshy: those to the right on Warwick Creek, except for one small marsh, form low bluffs.

In order that the mosaic may be compared with the map, Fig. 16, it has been placed with the northerly part at the top of the page, with the result that, until the page is reversed, the trees in the swampland appear like hollows in the earth. Scale, 1:14,000.

especially conspicuous. Streams appear as smooth, winding ribbons—glistening if the sunlight reflected from them enters the eye, dark if the bright rays are reflected away from the eye. Railroads can easily be traced and towns recognized by their form. Concrete roads and others of light-colored material are plainly visible. Those built of dark-colored material appear less prominently. Something even of the character of the forests can be ascertained—whether evenly timbered or partly of primary and partly of secondary growth; whether intact or partly burned over; whether consisting chiefly of one species of trees or of many. The cultivated fields and their relations to roads, streams, and forests are conspicuous. Towns and cities are spread out like panoramic views in which are strikingly visible the residence and manufacturing centers, the layout of streets, the systems of parks, the position of suburbs, and the relation of these to routes of transportation and travel—roads, railroads, and waterways. These and many other features of the landscape—swamps, marshes, buildings, trees, orchards, and many lesser details—are recognizable and are all recorded on the

Fig. 16—The same area as shown in Fig. 15 reduced from a section of a map on the scale of 1:10,000 by the Corps of Engineers, U.S.A. The photographs shown in Fig. 15 were used for mapping certain small features on this map, such as small streams. Scale, 1:14,000.

photographic negative. So faithfully does the camera reproduce all the horizontal features within its range of vision that it is conceivable that a photograph correctly dated might become a valuable record in cases of boundary disputes or other litigations involving the position of fences, fields, roads, or even streams, at a given date.

Fig. 17—Columbus. Ga. A part of a mosaic made at Camp Benning near-by in 1909 showing the town, river, and surrounding country. The scale is so small that buildings and trees appear as dots, city blocks as small parallelograms, streets and roads as light-colored lines. The cultivated fields appear as irregularly checkered areas, and the concentric lines of the terraced slopes have the appearance of contour lines on a topographic map (see Fig. 18). The picture illustrates many of the features of city geography. The comparatively straight course of the river and the heavy growth of trees and bushes along its edges indicate a minimum of flood-plain and steep banks—an inference supported by the fact that the principal business center of the city, shown by large, closely set roofs, is built close to the river. Surrounding this section is the most densely populated district, which in the northern part of the city gives way to a district of houses set farther apart and separated by lawns set with trees. Other less extensive business centers are shown as small spots of closely grouped buildings. A variety of suburban types is to be seen: some quite city-like, with a business center, a densely populated residential district, and a district of houses separated by grounds; others more village-like in their lack of a well-developed center but still more or less completely separated from the city proper; still others, sporadic scatterings of houses and grounds extending from the city for some distance along the principal roads. The railroad center is located conveniently near the business center, and the radiating lines of road and railroad communications are in strong contrast to the rectangular arrangement of the city streets. Factories, indicated by large, light-colored roofs, are located along the railroad in the southern part of the city and along the river to the north. Those along the river are operated by power from the falls which the picture shows. The terraced slopes are characteristic of the region, the farmers here and elsewhere in the South making these terraces in their plowed fields to prevent rain water from washing away the soil. Scale, about 1:38,000.

Fig. 18—Map of the same area shown in Fig. 17 enlarged from the corresponding sections of the 1:62,500 Columbus and Seale, Ga.-Ala., and the 1:125,000 Talbotton and Opelika, Ga.-Ala., topographic sheets surveyed mainly in 1906 and 1907 and published by the U.S. Geological Survey. The cross section at the bottom lies along the line indicated on the map and extends somewhat beyond the right border of the map. The section shows the broad shelf upon which the city rests and its relation to the river and to the terraced hillsides east of it. Scale, 1:38,000.

CHAPTER VI
MARSHES AND MARSH DRAINAGE
(Figs. 19 to 27)

Mention has been made of the objects seen better from the air than from any viewpoint on the ground; but there are some objects which as a whole can be seen only from above. Swamps, parts of everglades, peaks in the midst of difficult country, precipitous canyon walls, and many volcanic craters cannot be seen from the ground without undue effort. Photographs of bluffs, terraces, and other slopes facing bodies of water have hitherto been adequately obtainable only from the water. All of these can be readily viewed and photographed from the airplane. Pictorial representations of drainage systems were rare until photographs such as Figure 19 were taken from airplanes. The intricate drainage of marshes like those along the Pamunkey River in Virginia pictured in Figure 20 was never accurately shown until photographed from the air.

Of frequent occurrence on the Atlantic Coastal Plain of the United States are swamps and marshes inaccessible from the ground. Much of the surface material is so soft that they cannot be easily traversed; and, even where firm enough to support a man’s weight, few of the details are deemed of sufficient importance to warrant the trouble and expense of mapping by ordinary methods. Yet the trapper would scarcely admit that these details are unimportant, and, to the student, they are an interesting feature of marsh topography that has thus far received little attention.

Figure 25 is part of the excellent New Kent, Va., sheet of the topographic map and is probably as detailed as a map of this character should be when made from ground surveys only. However, on comparison of the map with a photograph of the same area (Fig. 24), there is no difficulty in detecting errors; and it is probable that, had the photograph been available when the map was made, the marshes would have been represented differently.

Fig. 19—Stream development in a tidal marsh, showing, at the right, the northern end of Ludlam Beach, about 6 miles south of Ocean City, N.J., and the mouth of Corsons Inlet leading to Ludlam Bay, and, at the left, the marsh just west of the inlet, with streams rising close to the bank of the larger stream at the extreme left and flowing in meandering courses across the marsh. The great variety of types of vegetation probably is one cause of the remarkable meandering of these drainage lines by reason of the fact that the accumulated remains as well as the annual growth of different weeds and grasses offer varying resistance to the current of the streams. Scale, about 1:10,000.