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The Project Gutenberg EBook of The Face of the Earth as Seen from the Air, by Willis Thomas Lee This eBook is for the use of anyone anywhere at no cost and with almost no restrictions whatsoever. You may copy it, give it away or re-use it under the terms of the Project Gutenberg License included with this eBook or online at www.gutenberg.org/license Title: The Face of the Earth as Seen from the Air A Study in the Application of Airplane Photography to Geography Author: Willis Thomas Lee Editor: W. L. G. Jeorg Release Date: May 9, 2020 [EBook #62068] Language: English Character set encoding: UTF-8 *** START OF THIS PROJECT GUTENBERG EBOOK THE FACE OF THE EARTH *** Produced by Chuck Greif, ellinora and the Online Distributed Proofreading Team at https://www.pgdp.net (This file was produced from images generously made available by The Internet Archive/Canadian Libraries) Contents. Index.: A, B, C, D, E, F, G, H, I, J, K, L, M, N, O, P, Q, R, S, T, U, V, W, Y. List of Illustrations In some instances, the captions have been reunited with the images, making the references to the "opposite" or "following/facing page" irrelevant. (In certain versions of this etext [in certain browsers] clicking on the image will bring up a larger version.) (etext transcriber's note) THE EARTH SEEN FROM THE AIR FIG. 1—The National Capitol, Washington, D. C. A view obliquely downward from a position over the National Botanical Garden, showing the western front of the Capitol at the approach to it from Pennsylvania Avenue. In the background, at the right, can be seen a part of the Library of Congress and, at the left, a part of the Senate Office Building. The radiating avenues of approach are of interest as well as the character of the district surrounding the Capitol, as indicated by the apartment houses and tree-lined streets. AMERICAN GEOGRAPHICAL SOCIETY SPECIAL PUBLICATION NO. 4 W. L. G. JOERG, Editor THE FACE OF THE EARTH AS SEEN FROM THE AIR A Study in the Application of Airplane Photography to Geography BY {i} WILLIS T. LEE U. S. Geological Survey AMERICAN GEOGRAPHICAL SOCIETY BROADWAY AT 156TH STREET NEW YORK 1922 COPYRIGHT, 1922 BY THE AMERICAN GEOGRAPHICAL SOCIETY OF NEW YORK CONDÉ NAST PRESS GREENWICH, CONN. CONTENTS CHAPTER PAGE Introduction ix I The Viewpoint 1 II Familiar Scenes From a New Angle 7 III Architecture, Landscape Gardening, and Engineering 11 IV The Mosaic 20 V General Aspects of the Surface As Seen From the Air 22 VI Marshes and Marsh Drainage 27 VII Coastal Mud Flats 41 VIII Submerged Land Forms 45 IX The Plain From the Air 50 X Mountain Features 57 XI Air Craft in the Study of Rocks and Ores 69 XII Mapping and Charting From the Air 72 Index: A, B, C, D, E, F, G, H, I, J, K, L, M, N, O, P, Q, R, S, T, U, V, W, Y. 105 LIST OF ILLUSTRATIONS (o) indicates an oblique, (v) a vertical airplane photograph FIG. PAGE THE VIEWPOINT, AND FAMILIAR SCENES FROM A NEW ANGLE 1 The National Capitol, Washington, D. C. (o) Frontispiece 2 Symbols of automatic register in the Eastman mapping camera (v) 3 3 The United States Military Academy, West Point, N. Y. (o) 8 4 The United States Naval Academy, Annapolis, Md. (o) 9 ARCHITECTURE, LANDSCAPE GARDENING, AND ENGINEERING 5 Monument Avenue, Richmond, Va. (o) 12 6 The United States Naval Observatory, Washington, D. C. (o). 13 7 Shipyards at Newport News, Va. (o) 14 8 The New York Connecting Railroad Bridge (o) 15 9 A part of Washington, D. C. (o) 16 {ii} {iii} {v} {iv} 10 Part of Rockaway Beach, Long Island, N. Y. (v) 17 11 Part of Long Branch, N. J. (v) 18 12 Benning, D. C., and the Anacostia River (v) 22 13 The land along the Anacostia River on the eastern edge of Washington, D. C. (v) facing 22 14 Map of the same area as in Fig. 13 facing 22 GENERAL ASPECTS OF THE SURFACE 15 Southeastern part of Mulberry Island on the lower James River, Maryland (v) 24 16 Map of the same area as in Fig. 15 25 17 Columbus, Ga. (v) facing 26 18 Map of the same area as in Fig. 17 facing 26 MARSHES AND COASTAL MUD FLATS 19 Tidal marsh and ocean beach at Corsons Inlet, New Jersey (v) 28 20 Details of marshland, Lee Marsh, lower Pamunkey River, Virginia (v) 30 21 Details of marshland, Cousaic Marsh, lower Pamunkey River, Virginia (v) 31 22 Barrier beach from Corsons Inlet to Atlantic City, N. J. (v) 32 23 A river system in miniature near Hampton, Virginia (v) 33 24 Sweet Hall Marsh on the lower Pamunkey River, Virginia (v) 34 25 Map of the same area as in Fig. 24, with cross section 35 26 Eltham Marsh on the lower Pamunkey River, Virginia (v) 36 27 Map of the same area as in Fig. 26, with cross section 37 28 A stream system of the mud-flat area off the Eastern Shore of Virginia (v) 42 29 Mud-flat streams (v) 43 SUBMERGED LAND FORMS 30 Stove Point Neck at the mouth of the Piankatank River, Virginia (v) 46 31 Gwynn Island at the mouth of the Piankatank River, Virginia (v) 46 32 Map showing the location of Figs. 31 and 32, with cross section 47 33 A drowned valley: Lambs Creek, Chesapeake Bay, Virginia (v) 48 THE PLAIN FROM THE AIR 34 The Chattahoochee River south of Columbus, Ga. (v) facing 50 35 Map of the same area as in Fig. 34 facing 50 36 A river channel in the Great Plains: The Red River northeast of Wichita Falls, Tex. (v) 51 37 A glacial drift plain in southwestern Michigan (v) 52 38 Map of the same area as in Fig. 37 53 39 Schoolcraft, Mich. (v) 54 40 Map of the same area as in Fig. 39 55 41 Kettleholes in glacial till southwest of Schoolcraft, Mich. (v) 56 MOUNTAIN FEATURES 42 Mt. Shasta, California (o) 58 43 A glacial gorge on the northeastern face of Mt. Shasta (o) 59 44 Yosemite Valley, California (o) 60 45 Map showing the angle of vision of Fig. 44 61 46 Cinder Cone on the eastern edge of the northern Sierra Nevada, California (o) 62 47 Map showing the angle of vision of Fig. 46 63 48 The top of Cinder Cone (o) 64 49 Simi Hills northwest of Santa Monica, Cal. (v) 65 50 Part of Santa Monica Mountains north of Santa Monica, Cal. (v) 66 {vi} {vii} 51 Map of the region between the center of Los Angeles and Santa Monica, Cal., showing the location of Fig. 50 67 52 A young mountain gorge in the San Joaquin Hills, a coastal range in Southern California (v) 68 53 Canyon in sedimentary rocks near the mouth of the Pecos River, Texas (v) 70 MAPPING AND CHARTING FROM THE AIR 54 View across the western end of Lake Erie (o) 73 55 Map showing the angle of vision of Fig. 54 73 56 Rochester, N. Y. (v) facing 74 57 Map of the same area as in Fig. 56 facing 74 58 Index map showing the location of the airplane photographs in this book taken on the Atlantic seaboard of the northeastern United States 75 59 Marshlands on Chesapeake Bay south of the mouth of the York River, Virginia (v) 76 60 Left shore of the York River northwest of Gloucester Point, Va. (v) 77 61 The northwestern tip of Sandy Hook, New Jersey (v) 78 62 Beach cusps under water near Beach Haven, N. J. (v) 80 63 First stage in the formation of an inlet through a barrier beach: near Beach Haven, N. J. (v) 81 64 A tidal delta in Shark River Inlet, Belmar, N. J. (v) 82 65 A tidal delta, Popes Creek on the lower Potomac River, Virginia (o) 83 66 A double tidal delta at Barnegat Inlet, New Jersey (v) 84 67 A tidal inlet through the barrier beach south of Beach Haven, N. J. (v) 85 68 Beach between Brigantine and Little Egg Inlets, New Jersey (v) 86 69 A simple spit: Lower Cedar Point, Maryland, on the lower Potomac River (o) 87 70 A recurved spit south of Brigantine Inlet, New Jersey (v) 88 71 A recurved spit showing interference with natural growth: The northern end of Ocean City, N. J. (v) 89 72 New Point Comfort at the tip of the York-Rappahannock peninsula, Virginia (v) 90 73 Spit at Tucker Beach, New Jersey (v) 91 74 A land-tied island: Napatree Point, near Watch Hill, R. I. (v) 92 75 Powells Creek, Virginia, on the lower Potomac River (o) 93 76 Roberts Creek, a drowned river valley southeast of Yorktown, Va. (v) 94 77 The underwater channel in Quantico Bay on the lower Potomac River, Virginia (v) 95 78 Natural channels and shoals near Miami. Fla. (o) 96 79 A dredged channel at Miami, Fla. (o) 97 80 A shoal in Hereford Inlet north of Wildwood, N. J. (v) 98 81 Sand bars at Cape Charles, Va. (v) 99 82 Bars, channels, beaches, and marsh near Far Rockaway, Long Island, N. Y. (v) 100 All of the airplane photographs in this book, both oblique and vertical, were taken by the United States Army Air Service, except Figs. 78 and 79, which were taken by the United States Navy Air Service, and Figs. 10, 65, 69, 75, 77, and 82, which were taken by the author. To these two services the author is indebted for the permission to reproduce their photographs, and this acknowledgment is made with the same force as if made individually under each illustration. As a guide to the evaluation of the scale of the vertical photographs, which is expressed under each photograph in the form of the natural scale, or representative fraction, the following approximate equivalents may be borne in mind: 1:10,000 = 800+ feet to the inch 1:16,000 = ¼ mile to the inch 1:21,000 = ⅓ mile to the inch INTRODUCTION Scarcely a generation has passed during the evolution of the airplane from a ridiculous dream to a practical factor in the work of the world. Men who once read with derision, or only passive interest at best, of the experiments of Langley, Chanute, and the Wrights have seen the airplane developed suddenly into an indispensable instrument of war and an agency of demonstrated value and of such diversity of application that its future is hard to estimate. The navigation of the air has accomplished much in many fields. Not only does it offer a new means of efficiency in military reconnaissance, rapid delivery of mail, fire patrol of forests, and the constantly increasing number of commercial and scientific pursuits {viii} {ix} to which it is being adapted; but it has also opened a new world to the geographer, the physiographer, and the geologist. AIRPLANE PHOTOGRAPHY: ITS DEVELOPMENT AND APPLICATION Very early in the war the airplane was recognized as a useful, in fact a necessary, means of observing enemy positions and movements. But the speed of the airplane was found to preclude the taking of more than the most hurried of notes during a flight, and notes written from memory are not the most satisfactory. Photography was found to obviate this difficulty. The ability of the camera to make instantaneous exposures and fix a clear image on a photographic plate enabled the observer to obtain a record not only of the scenes that he had viewed but also of many that he might have missed while engaged in the necessary business of watching the sky for the enemy—a record that for detail and accuracy could not be approached by the most elaborate notes or the most graphic description. Immediately inventive genius was set at work to adjust the mechanism of the camera to the demands of air photography and to prepare the rapidly working films and highly sensitized paper necessary for the best results. So satisfactory were the results and so great are the possibilities of further adaptation that there is an unfortunate tendency on the part of certain enthusiasts to make exaggerated claims that may react to retard progress. This is particularly true in the use of the air photograph in mapping. There are limitations to this use of air photography. It cannot be reasonably expected to do away entirely with the ground work of the surveyor. Rather, the camera is to be regarded as one of the instruments of the surveyor. Observation from the air can never take the place of close examination of the ground, but it can be of great use in the location and study of land forms and geologic relations. Air photography is only an added means of obtaining information, although it promises to become a very important means. Observations from the air described in numerous reports and articles in geographic magazines during the war and since its close indicate that air craft, especially in connection with air photography, can be of great use in studying the physical features of the face of the earth. In order to make a practical test of the use of the airplane in the study of geography the writer spent about nine months during the year 1920 making flights, taking pictures from air craft, and gathering information from various sources. This book embodies the chief results. The material presented here is by way of illustrating the possibility of using the airplane and airplane photography as a means of securing information that should become increasingly useful in the study of geography, and of showing geographic and geologic features better than in any other way. The views have been chosen to illustrate the three uses of air photographs with which this book deals— the presentation of new views of subjects of popular interest and the practical value of such views; the study of land forms from a new and advantageous point of view; and the use of the air photograph as an aid in mapping. In presenting these illustrations there is no intention that the list of types should be considered in any sense complete. Physiographic observation from the air is a relatively new undertaking, and results are limited and imperfect. As improvements in mechanism and technique are made, observations will be extended and better photographs and a greater variety of them will be secured. Such as are presented here, however, serve to demonstrate that the air photograph will come to be recognized as a valuable source of information for the student of geography and geology. ACKNOWLEDGMENTS The results here presented were secured by the co-operation of the Air Services of the United States Army and Navy. Hydroplanes were placed at my disposal on several occasions, and a number of flights were made over water bodies, particularly over the Potomac River, Chesapeake Bay, and New York Harbor. But the information was gathered chiefly through the Army Air Service. Many flights were made in army planes, some for general observation, others for photographing specific objects. Also the army photographers, particularly those at Langley Field, near Newport News, Va., made several photographic trips at my request, and a large number of prints were furnished from negatives stored at this and other flying fields. In this connection I wish to express appreciation for the many courtesies extended by Major General C. T. Menoher, U. S. A., Chief of Air Service at the time the work was done, and by Major J.W. Simons, Jr., A.S., Acting Administrative Executive, Air Service. These officers placed at my disposal every facility of the service that I could use. It would be a pleasure, if space allowed, to mention the names of the numerous pilots and other officers to whom I am directly indebted for the safe completion of some of the most thrilling adventures of my life. I must, however, mention the officer to whom I am perhaps more indebted than to any other. My introduction to this study was through Major J.W. Bagley of the United States Army Engineering Corps, who has done much toward making the camera a valuable instrument in mapping.[1] Through his active interest I became acquainted with the officials of the Army Air Service, who gave the necessary authorization for flights and for securing most of the photographs used to illustrate this book. During the time spent at this work I retained my position as geologist of the United States Geological Survey. Hence the work is one of co-operation chiefly between the United States Army Air Service and the United States Geological Survey, and to a lesser degree with the United States Navy Air Service. CHAPTER I THE VIEWPOINT (Figs. 1 to 4) OBLIQUE AND VERTICAL AIRPLANE PHOTOGRAPHS {x} {xi} {xii} {1} Air photographs are, in general, of two sorts, depending upon whether the photograph was taken with the camera pointing vertically or obliquely downward. In either case the air photographer is free from the limitations that hamper the ground photographer in choosing a point of view. For he can ascend to any desired height and not only select an advantageous position from which to photograph the feature which he wishes to emphasize but also, at the same time, avoid obstacles which might obstruct his view from the ground. Vertical photographs are preferable where the accurate location of objects is desired. When properly taken they serve many of the purposes of maps and are, in many ways, even more useful than maps. They furnish the untrained mind with much of the information that the trained mind reads from a topographic map and, in addition, supply details and relations that a map cannot depict. Exact accuracy, however, cannot be claimed for them until they have been corrected for distortion and adjusted to some system of controls. Where the photograph is to be used as a means of securing a more advantageous view of a subject than can be had from the ground rather than as a map on which distances are to be scaled off, the oblique photograph is probably the more desirable, since it is as easily intelligible as a photograph taken laterally. The advantage of such photographs is obvious. To the architect, the landscape gardener, the city planner is given the opportunity to study their projects free from all obstructions yet in such perspective that their relations to their surroundings are brought out as would be possible by no other means. Views like that of West Point (Fig. 3) are occasionally to be had from some hilltop, but the limited choice of position on the ground contrasts sharply with the unlimited choice in the air. ELEMENTS TO BE RECORDED Air photography is by no means simple. Much still remains to be done by way of adapting the camera to its peculiar demands. Its present degree of perfection, of course, is largely due to the impetus given its development during the war because of its great importance in military reconnaissance. The adaptation of the camera to operation from the airplane might be described with profit but will be passed with slight mention because it is the results of air photography rather than the mechanism that are to be considered here. Technically, a photograph of the earth’s surface may not be a map, but, given certain means of interpretation, it can be made to serve as such. In using air photographs, particularly the vertical ones, it is desirable to know the scale, which is dependent upon the altitude at which the exposure is made; the angle of the lens; and the variation from the vertical, in order to make corrections for distortion. Therefore, it is desirable that each photograph show the altitude, date, time of day, and position of the lens at which the exposure was made. Cameras have been constructed that automatically record these data on each negative. This information is illustrated in Figure 2. The circular symbol at the left in the white strip at the top of the photograph represents a circular level, or inclinometer. The small round dot close to the center of the inclinometer indicates that, at the time the exposure was made, the axis of the lens was very nearly vertical. The symbol in the center of the white strip indicates an altitude of about 9,800 feet, and that at the right, that the exposure was made 7 seconds after 11 A.M. The other symbols record that this photograph was No. 13 of a series made at Rochester, N. Y., October 23, 1920, with an Eastman mapping camera known as K-2. The symbol 8-P is non-essential and records that this negative is No. 8 of panchromatic film. FIG. 2—Symbols of automatic register in the Eastman mapping camera, photographed with the body of the picture showing roads, streams, orchards, cultivated fields, etc. For explanation of the symbols, see the text. The information given by the symbols is corroborated by the picture. Orchard and shade trees appear as circular dots in place of the elongated images characteristic of pictures taken obliquely downward, and the short, squat shadows denote exposure near midday. Shocks of corn standing in the fields show that the season is autumn. HOW TO READ AIRPLANE PHOTOGRAPHS Not all the features, however, are so easily recognizable. Oblique photographs are often more readily interpreted than ordinary photographs, since they combine with the usual view the essentials of a plan; but in vertical photographs very few objects present an appearance that is natural in the light of our experience as lateral observers. The uninitiated, on attempting systematically to identify the features of a vertical photograph, find a very large number that are foreign in appearance. A necessary preliminary is an acquaintance with the ground photographed or with similar regions and features. Without such a key the air photograph is not always self- interpretative and is often unintelligible. Military observers are carefully trained to recognize features of military significance. It is not to be expected, however, that they should be trained in the observation of land forms except such as are of military importance. Consequently, whereas a great variety of photographs is now easily obtainable at many flying fields, the information that a scientist would desire concerning them is not so easily available. Most of the photographs used in this paper were taken by men who were not trained in observing land forms. Many were taken simply as a requirement in practice flights and meant so little to the observer that no record was made concerning them. For several not even the location was recorded. It is of primary importance that the picture be held in the right position. Not only must the observer imagine himself looking directly down on the scene but he must hold the photograph in the position in which experience has shown that the image appears the most natural. Otherwise a depression will appear as an elevation and an elevation as a hollow. It is a well-known fact that in telescopic photographs of the moon the craters appear like hollows when the print is held in one position and like elevations when the position is reversed. Experience shows that if the print is held so that the shadows fall toward the observer the objects appear natural. The reason is that the observer sees only those shadows that are caused by light falling towards him. Consequently, the only interpretation that the brain can give to shadows on a photograph is that they are cast by an elevation between the eye and the light. In a picture, {2} {3} {4} {5} therefore, in which shadows fall away from the eye instead of towards it valleys are seen as hills and hills as valleys. In the northern hemisphere this prescribed orientation conflicts with the convention of placing the north side of a map at the top of the page and also with the modern shaded map on which the light is represented as coming from the upper left, or northwest, corner of the map. FAILURE OF AIR PHOTOGRAPHS TO SHOW RELIEF, AND MEASURES TO REMEDY THIS DEFECT In photographs taken from the ground the lights and shadows are such that a high degree of naturalness is possible. But objects seen from directly above, and even those viewed obliquely, though to a lesser degree, are illuminated so uniformly that photographs of them are apt to appear flat. To some extent this has been overcome by the use of extra-sensitive emulsions, special ray filters, and printing papers adapted for accentuating contrast. Many of the photographs used in this book did not allow satisfactory reproduction till the contrast of the negatives was greatly increased by the arts of the photographic laboratory. But, even at its best, no photograph taken vertically affords an adequate idea of the height of hills or the depth of hollows. Only shadows that are particularly well defined can be distinguished as shadows, while small elevations and depressions affect the negative no differently than a difference in marking or color. In military defenses, if the mere surface of the camouflage is sufficiently realistic, the ordinary camera is even more easily deceived than the human eye. It is a well-known fact that man and other animals of the higher order see objects in relief, within a certain range of vision, because the eyes convey to their respective retinas slightly different images of the same object which the brain combines into a relief image. The stereoscopic camera has long been used for the same purpose. Its principle, with certain adaptations that need not be discussed here, has been to some extent employed in airplane pictures, with such excellent results that it is claimed by some that by further development actual contouring will be possible by this means. It is reported that in military reconnaissance stereoscopic pictures render ordinary camouflage useless and that bridges, observation towers, gun emplacements, etc., are shown in relief and, therefore, easily detected.[2] CHAPTER II FAMILIAR SCENES FROM A NEW ANGLE (Figs. 1, 3, and 4) Pictures of well-known buildings are of wide appeal. In so far as they create an interest in the activities for which the buildings stand they are distinctly educative. Such widely known buildings as the National Capitol and the Library of Congress are used repeatedly for illustration. They are as welcome as the sight of a familiar face. Any unusual circumstance connected with them is seized upon as an excuse for republishing pictures of them. Views of them from a new angle are always in demand. Not only do air photographs offer a welcome novelty, but they have the added advantage of lifting the subject out of the clutter of surrounding buildings and making it really the central figure of the picture. It would be difficult to get a more impressive view of the National Capitol than that of Figure 1 or a more attractive glimpse of the Naval Academy at Annapolis than that of Figure 4. The objects of chief interest occupy the center of view without distracting obstructions. In the former, the imposing structure of the Capitol building appears in a pleasing setting of minor details. The proximity of the Senate Office Building and the Library of Congress is at once apparent, and the radiating systems of the avenues of approach. Strangers may have wondered as to the nature of the environs of the Capitol. The tree-lined streets and the apartment houses seen in the picture answer the question. In the view of the Naval Academy the buildings occupy the center of the scene, with the beautiful dome of the memorial to John Paul Jones, the first great American naval fighter, prominently in view. Spa Creek in the foreground, a part of the capital city of Maryland at the left, and the Severn River, with its low wooded banks, stretching away FIG. 3—West Point, N. Y., and the Hudson River. An air view of the United States Military Academy and the gorge of the Hudson. The picture shows the commanding view of the river to be had from the point of land 180 feet above the river on which the Military Academy is located and shows the wisdom of the choice of this spot as one of the chain of redoubts by which the river was fortified during the Revolution. FIG. 4—The Naval Academy at Annapolis, Md. Oblique view from an airplane from a position over Eastport in a general northwesterly direction. The water in the foreground is Spa Creek. The Severn River, spanned by the county bridge and the Baltimore and Annapolis Railroad bridge, stretches away to the left. The buildings in the middle of the picture are those of the Naval Academy. The domed mausoleum built in honor of John Paul Jones, which serves as his final resting place, appears at the left. Still farther to the left lies Maryland’s capital city. Of interest is a comparison of the low-lying and stream-cut banks of the drowned valley now occupied by the Severn River with the mountains through which the Hudson River has cut its gorge at West Point (see Fig. 3). in the distance, spanned by the county bridge and the Baltimore and Annapolis Railroad bridge, form an interesting setting and show, without detracting from the importance of the academy itself, its advantageous location with regard to the city and the water approaches. CHAPTER III ARCHITECTURE, LANDSCAPE GARDENING, AND ENGINEERING {6} {7} {8} {9} {10} {11} (Figs. 5 to 14) Only a few photographs are necessary to show how valuable to the architect, the construction engineer, the city planner, or the landscape gardener the air photograph, both vertical and oblique, is destined to become. Pictorial records of progress in the construction of buildings, bridges, ships, canals, reservoirs, etc., that partake also of the nature of ground plans, as do air photographs, furnish an admirable means of study and comparison. No photograph of the great shipyards at Newport News taken from the ground would show the relation of the shops and drydocks to the deep-water approaches as does Figure 7. Figure 8 gives an unusually comprehensive idea of the location, magnitude, and construction of Hell Gate Bridge; and Figure 10, Rockaway Beach, now a densely populated town where a few years ago was a barren strip of sand, suggests that photographic records of construction in rapidly growing communities where changes are being made in streets, railroads, and buildings, will come to be a part of the equipment of the city engineer and architect. ARCHITECTURE AND LANDSCAPE GARDENING Equally useful will the air photograph become to the landscape gardener and architect. Heretofore, in order to get a comprehensive conception of his task and a definite picture of its completion, the landscape gardener has had to depend upon the use of maps and such views as could be made by the sketch artist or the ordinary lateral photograph. In the future, from vertical and oblique photographs of the area to be developed, he will have the means of studying its features in their correct proportions and relationship. By means of similar photographs of completed projects he can choose and combine until he has developed the plans best suited to his purpose. He can bring to his aid first-hand studies of gardens and grounds the world over whose beauties have made them famous. FIG. 5—Monument Avenue, Richmond, Va., and the statue of Robert E. Lee. An oblique photograph illustrating the use of aerial photography in landscape gardening and street planning. 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 {12} {13} {14} {15} {16} {17} {18} {19} 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. {19} {20} {21} {22} 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 {23} {24} {25} {26} {27} 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. MARSH DRAINAGE One of the most striking characteristics of marsh topography illustrated by the photographs presented here is the great wealth of drainage lines and the resemblance of the drainage patterns to those of river systems developed on higher ground. The dendritic patterns, the meanders, and the sharply outlined divides are surprising in areas which have altitudes varying from only a few inches to a little more than a foot at times of ordinary high tide and which are wholly submerged at times of maximum tide. Some of the streams have gently winding courses suggestive of normal stream development. Others, particularly the smaller, have a conspicuous angularity of course. It is possible that the latter may have originated as the trails of animals. Some of the lines are observed to cross the larger streams and are probably tracks made by muskrats. Some of the streams rise close to the river’s brink and lead to through-going waterways near the center of the marsh. This suggests the deposition of silt on the brink of the river at times of high water. The notched appearance of the shore in Figure 20 seems to be due to overhanging bunches of sedge grass and, in some instances, to the breaking away of the surface mat or crust of the marsh formed by the interlacing roots of grass. The mottled appearance of the marsh in this picture may be partly due to shadow of clouds, but to some extent, at least, the difference in shade is caused by differences in the character of the plants. The marshes used for illustration here are typical of many along the Atlantic Coast. They are situated near West Point, Va. The Pamunkey and the Mattaponi Rivers both rise in the Piedmont Plateau, flow southeastward through the tidewater portion of Virginia, and join about midway of the Coastal Plain to form the York River[3] (see Fig. 58). FIG. 20—Details of marshland. A part of Lee Marsh near West Point, Va. (cf. Fig. 26), as photographed from a height of 2,000 feet, June, 1920. Local observers report that this marsh has been submer...

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