CHAPTER XII

MAPPING AND CHARTING FROM THE AIR

(FIGS. 54 TO 82)

Mention has already been made (p. 56) of the experiment in map-making carried out by the Army Air Service and the United States Geological Survey at Schoolcraft, Mich. The results of that experiment and of others of the sort are sufficient to establish the fact that the air camera is destined to become a valuable addition to the map-maker’s equipment. The extent to which it will be used depends, of course, upon the degree to which its present imperfections are corrected and its possibilities developed. The Board of Surveys and Maps of the United States government has recently published the results of its study of air photography for use in map-making.[6]

SCALE AND HORIZONTAL CONTROL OF VERTICAL PHOTOGRAPHS

The vertical photographs taken with an air camera are, of course, of the order of large-scale maps.[7] For a lens of 6-inch focus the scale at an elevation of 2,500 feet will be 1:5,000; at 5,000 feet, 1:10,000; and at 10,000 feet, 1:20,000.[8] Air mapping, therefore, lends itself best to the production of such maps as engineering maps, city plans, topographic maps, and coast charts. In all of these maps a degree of accuracy is demanded that will give the exact location of all the features included on the map and permit the precise measurement of distances between them. To obtain such accuracy necessitates an elaborate system of control stations as a basis on which the surveyor works out his triangulations and traverses. In the United States these controls have been established principally by the United States Coast and Geodetic Survey.[9] To construct a map from air photographs, varying in scale and distorted as they often are because of the impossibility of holding the plane at an absolute level and because of the stretching or shrinkage of the photographic paper, would require a great amount of triangulation and traverse in order that the control might be sufficiently detailed to permit the accurate mounting of the photographic prints. But, given these controls, the air camera can, without further adaptation, supply details that heretofore required the laborious processes of plane-table mapping. The topographer can place the two-dimensional details from photographs and then go into the field with only the contouring to be done.

USE IN CITY MAPPING

In city mapping, even though time be taken to establish a very elaborate system of controls, the air camera can accomplish in a few hours a task of years by ordinary methods. In fact it is only by means of air photographs that maps of a growing city can be kept at all up to date. Paris was mapped with 800 plates in less than one day of actual flying. Washington was completely mapped in two and a half hours with less than 200 exposures.[10] For the mosaic of Rochester, N. Y. (Fig. 56) 82 photographs were made in one hour and twenty minutes. There is no reason why such a mosaic with an original survey or even a number of accurately located points as a basis of control should not be sufficiently accurate for all purposes.

USE IN REVISION OF EXISTING MAPS

Another immediate use of air photographs in mapping is in the correction and revision of existing maps. So far as individual features are concerned, the air photograph is an exact record of the area exposed to its lens, and natural and artificial features are easily transferred from the picture to the map. Its great value in the saving of time and money has been demonstrated in the rapidly developing territory near Los Angeles. In 1893 the Santa Monica quadrangle was surveyed, and houses, roads, etc., as they existed at that time, are shown on the map. This area was later built up and so changed that the map was practically worthless. From information derived from air photographs the map was revised in 1920 (Fig. 51). Evidence has already been given of the efficiency of the air photograph in elaborating maps where the importance of the region is not sufficient to warrant the expense of a detailed survey of minor features, and in mapping areas inaccessible from the ground.

USE IN COAST CHARTING

It is fortunate for those engaged in the study of shore features and the mapping of coasts that, being flat, shore features are particularly well adapted to representation by air photographs, for on coasts exposed to the wind and waves the channels, shoals and bars are continually changing. Air photography offers a quick and convenient means of keeping charts up to date. The intricacies of the water line in some places makes accurate charting by the ordinary survey methods a slow, laborious process. When bluffs or relatively steep slopes, like those of York River, Virginia, near Gloucester Point, shown in Figure 60,

occur along the shore, the water line varies little from year to year. But on very low lands, like those along Chesapeake Bay south of the mouth of York River, shown in Figure 59, the strand may migrate over a broad belt between high and low tide. For this reason it is desirable that photographs of areas affected by the tide be accompanied by a record of the date and time of day at which the exposure was made, in order that the height of the tide at the time of exposure can be computed. As the shore on the Coast and Geodetic Survey charts denotes the water line at high tide, a photograph taken at low tide might be interpreted as indicating an error on the chart. Where the water migrates over such a broad belt of sand or mud, the problems of charting become very troublesome. Photographs of such areas could be taken at both low and high tide, and from these the belt of daily flooding could be charted.

EXPERIMENTS BY THE UNITED STATES, FRENCH, AND OTHER COAST SURVEYS

The use of photographs in charting the coast line was tested by the United States Coast and Geodetic Survey.[11] A flight was

made over the coast of New Jersey by Captain A. W. Stevens of the United States Army Air Service, March 20, 1920, in a plane equipped with a K-1 camera of 10-inch focal length, which makes negatives 18 by 24 centimeters in size. During the flight the camera was maintained at an altitude of about 10,000 feet. The course was covered by 183 exposures made at such intervals of time that the prints overlap. Unfortunately the exposures were not sufficient to give all the details desired for marsh and water areas, but prints were made on developing paper suitable for showing extreme contrast. These were matched together and a continuous picture obtained. A part

of this picture, greatly reduced, is reproduced as Figure 22. Several characteristic shore and salt marsh features are illustrated by this series of photographs, and these are reproduced in separate figures together with illustrations of special features in other places.

The main features illustrated in detail, all of which are continually liable to change, making the keeping of a map of the area at all up to date impossible by ordinary means, are as follows: coast of low-lying mainland (Fig. 60); mud or peat-covered beach (Fig. 59); sandy beach (Fig. 63); barrier beach (Fig. 67); beach cusps (Figs. 61 and 62); recurved spits or sand hooks (Fig. 70 and others); compound hook (Fig. 72); lines of growth in the development of hooks (Figs. 73); tombolos and tied islands (Figs. 60 and 74).

Another experiment was made by the Coast and Geodetic Survey off the coast of Florida, where the water is clear, in an attempt to photograph “the small coral heads and pinnacle rocks” which may be disastrous to boats. The report states that the results were unsatisfactory and concludes that airplane pictures are useful in “aerial photo-topography” but not in

“aerial photo-hydrography.”[12] On the other hand, Volmat reports the successful use of air photography for similar purposes on the French coast, where photographs of objects down to a depth of 17 meters (about 56 feet) were found useful in several ways--among others, the discovery of points of rock which had

escaped attention during very detailed surveys. He states that with proper plates and ray filters the presence of objects invisible to the eye is revealed by the camera.[13] Similar use of air photographs has been made by the English in charting reefs, shallows, and harbors. Thomas says: “In 1917 aeroplane photography was successfully used for charting the harbor of Rahbeg on the Arabian coast.”[14] It is a well-known fact that, under proper conditions, objects submerged to a considerable depth under clear water can be seen from points high above the surface. During the war, submarines were detected and followed by observers in airplanes, and sunken vessels, mines, and other submerged objects have been located by observation from the air. Illustrations in this paper show the possibility of using this method of observation, to some extent at least, in detecting and mapping shoals, channels, and other features under water.

Photographs of channels like those of the Potomac River and its tributaries will be commercially as well as scientifically valuable. The deep-water channel of the Potomac is well known and has been charted; but very little is known of many of the small tributary channels, such as that of Powells Creek (Fig. 75). Where the channels are not well known, such a photograph could be used to advantage in avoiding the shoals, and, by surveyors, first in exploratory work and later as a general guide in charting. Small boats entering this channel could use the photographs either for the original location of the deep channel in case no chart were available or for detecting changes in its course after the chart was made. For uncharted channels, like those of many of the tributaries of the Potomac River, air photography furnishes a quick and accurate means of location.

No amount of sounding, charting, or description could produce so accurate a mental picture of a drowned valley as that produced by Figure 76. In Figures 78 and 79, both of which were taken near Miami, Florida, is illustrated the difference in appearance between natural and artificial channels. The straightaway course and regular outlines of the dredged channel contrast sharply with the winding course and merging outlines of the natural channel. To the student of physiography and earth history the photographs furnish a means of observation of a definiteness heretofore quite unthought-of. On them the actual shape of the channels, submerged terraces, and drowned land forms are shown in detail.

IMPROVEMENTS UNDER WAY POINT TO PROMISING OUTLOOK FOR AIRPLANE PHOTOGRAPHY

There is, however, need of careful research to determine the conditions under which the best results can be obtained. The height and time of day for exposures with a certain lens, the emulsion and kind of ray filter best suited under certain conditions, the effect of light as it enters and emerges from the water, and the effect of polarization are subjects demanding consideration. Chief among the experiments now under way is the determination of the kind of emulsion and ray filter or color screen that will give the best results. It is a demonstrated fact that, with an emulsion sensitive to red light, objects in the air invisible to the eye because of intervening haze can be photographed through a red filter. It is possible that water can be penetrated in the same way and that filters of other colors will prove advantageous.

Certainly, the air photograph is only in its infancy--but an infancy full of promise. As a means of securing new and advantageous views of subjects of interest, it is not only entertaining but scientifically and commercially valuable. As an aid in mapping it can, even in its present stage of development, serve an important purpose by supplying accurate knowledge of otherwise inaccessible regions, by furnishing details that are valuable but expensive to obtain, and by permitting the frequent and inexpensive revision of existing maps.

INDEX

Accuracy, 1, 74

Acknowledgments, viii, xi

Aerial photo-hydrography, 99

Aerial photo-topography, 93

Air photographs, how to read, 4; improvements under way, 102; oblique and vertical, 1; value in coast charting, 93, 99, 101

Air photography, application, ix; development, ix; elements to be recorded, 2; outlook, 102

Air Services, co-operation, xi

Aircraft, x

Airplane photography. _See_ Air photography

Aliso Creek, California, 68

Amundsen, Roald, 71

Anacostia flats, D. C., 12

Anacostia River, 13, 22 (ill.); land along, mosaic photograph, opp. 32 (Fig. 13)

Animal trails, 29, 39

Annapolis, 7. _See also_ United States Naval Academy

Arabian coast, 101

Architects, 7, 11

Architecture, 11

Arizona, southern, 71

Arroyos, 61, 65 (ill.)

Atlantic City, N. J., 32 (ill.)

Atlantic Coastal Plain, 27; meandering streams, 50; salt marsh areas, 32 (ill.); submarine land forms, 45

Atlantic Ocean, waves and surf, 91 (ill.)

Back River, Virginia, 76

Bagley, J. W., xii, 74

Baltimore and Annapolis Railroad bridge, 9 (ill.), 10

Barnegat Bay, 85

Barnegat Inlet, 84 (ill.), 85

Barrier beaches, 41; between Brigantine and Little Egg Inlets, New Jersey, 86 (ill.); cities and surroundings, 32 (ill.); inlet formation through, 81 (ill.); Long Branch, N. J., 18 (ill.); tidal inlet through, Beach Haven, N. J., 85 (ill.). _See also_ Beaches

Beach Haven, N. J., cusps, 80 (ill.); inlet formation through barrier beach, 81 (ill.); tidal inlet, 85 (ill.)

Beaches, bluff and beach on shore of York River, 77 (ill.); cusps near Beach Haven, 80 (ill.); Far Rockaway, Long Island, 100 (ill.); sandy, with cusps--Sandy Hook, 78 (ill.). _See also_ Barrier beaches

Bear’s Cut, Florida coast, 96 (ill.)

Belmar, N. J., tidal delta, 82 (ill.)

Benning, Camp, opp. 26, opp. 50

Benning, D. C., 13, 22 (ill.)

Benning Road, 13

Benning Road Bridge, opp. 22 (ill. and map)

Bidwell, Lake, California, 62 (ill.), 63 (map)

Bluffs, 83; beach and bluff on shore of York River, 77 (ill.)

Board of Surveys and Maps, 72

Boundary disputes, 26; Texas-Oklahoma, 51 (ill.)

Braided channels, 50, 51 (ill.)

Brigantine Inlet, New Jersey, 86 (ill.), 87; recurved spit, 88 (ill.)

Bridges, 11; Baltimore and Annapolis Railroad, 9 (ill.), 10; Benning Road, opp. 22 (ill. and map); Hell Gate, 11, 15 (ill.); Pennsylvania Avenue, opp. 22 (ill. and map)

Bronx Borough, Port Morris section, 15 (ill.)

Bronx Kill, 15 (ill.)

Brooks, A. H., 69, 71

Buildings, construction records, 11; pictures from a new angle, 7

Calabasas, Cal., topographic sheet, 65

Cameras, adaptation, 2; automatic data records, 2; construction experiments, 35; Eastman mapping, recording symbols, 2, 3 (ill.); faithfulness, 23, 26; human eye and, 5, 101; panoramic, xii; stereoscopic, 6; use, x; use in map-making, 72; value in coast charting, 93, 99, 101

Camouflage, 5, 6

Camp Benning, Ga., opp. 26, opp. 50

Canyons, 57; Pecos River, 70 (ill.); Santa Monica Mountains, 66 (ill.), 67 (map)

Cape Charles, Virginia, 43; sand bars, 99 (ill.)

Capitol, National, frontispiece, 7

Catawba “Island,” Ohio, 72, 73 (ill. and map)

Channels, Far Rockaway, Long Island, 100 (ill.); Miami, Fla, 96 (ill.), 97 (ill.), 102; Potomac River, tributary, 101; underwater, 93 (ill.), 94. (ill.), 95 (ill.)

Chanute, Octave, ix

Charting, 72; coast, 83, 88

Chattahoochee River, opp. 50 (ill. and map)

Cherry Point, Virginia, 46 (ill.), 47 (map)

Chesapeake Bay, xi; Lambs Creek on, 48 (ill.); low lands along, 87; marshlands difficult to chart, 76 (ill.); wavy surface, 90 (ill.).

Cinder Cone, California, 57, 62 (ill.), 63 (map); top, 64 (ill.)

City geography, 17 (ill.), opp. 26, 54 (ill.), opp. 74, 79

City planners, 1, 11

City planning, 12 (ill.); Columbus, Ga., opp. 26 (ill. and map)

Clouds Rest, California, 60 (ill.)

Coast Charting, 83, 88

Coast surveys, experiments in mapping in United States, France, etc., 88

Coastal mud flats. _See_ Mud flats

Colonial Beach, Va., 83, 87

Color screen, 102

Columbus, Ga., opp. 26 (ill. and map); meanders near, 50, opp. 50 (ill. and map)

Columbus, Ga.-Ala., topographic sheet, opp. 50

Construction records, 11

Controls, 74

Coral islands, 93

Corona, Cal., topographic sheet, 68

Corsons Inlet, New Jersey, 28 (ill.)

Cousaic Marsh, Virginia, 34 (ill.), 35 (map); details, 31 (ill.)

Craters, 27, 57; Cinder Cone, California, 62 (ill.), 63 (map), 64 (ill.)

Cusps, Beach Haven, New Jersey, 80 (ill.); Sandy Hook, 78 (ill.)

Dayton, Ohio, 56

Deanewood, D. C., 13

Deltas, underwater, 33 (ill.), 45, 82 (ill.), 83 (ill.), 84 (ill.), 85 (ill.)

Depressions and elevations, interpreting, 4, 5

District of Columbia, Anacostia flats, 12

Drainage systems, 27; Lee Marsh, Virginia, 30 (ill.). _See also_ Marsh drainage

Drowned topography, 45; terraces at mouth of Piankatank River, 46 (ills.); valley--Lambs Creek, Virginia, 48 (ill.); valley--Roberts Creek, Virginia, 94 (ill.), 102

East Rockaway Inlet, Long Island, 100 (ill.)

Eastern Shore of Virginia, 41; mud-flat area, stream system, 42 (ill.), 43 (ill.)

Eastman mapping camera, opp. 74; recording symbols, 2, 3 (ill.)

El Capitan, 60 (ill.)

Elevations and depressions, interpreting, 4, 5

Ellipse, Washington, D. C., 16 (ill.)

Eltham Marsh, Virginia, 36 (ill.), 37 (map), 39

Emulsions, 102

Engineering, 11; projects covering large areas, 12, opp. 22 (ill. and map)

Erie, Lake, 72, 73 (ill. and map)

Erosion, headward, 57, 65 (ill.), 68 (ill.)

Everglades, 27

Exploration, 71

Exposure, 102

Eye versus camera, 5, 101

Far Rockaway, Long Island, 100 (ill.)

Filters, 102

Fishing Bay, Virginia, 46 (ill.), 47 (map)

Flats. _See_ Mud flats

Flood plain, 33 (ill.)

Florida coast, channels and shoals near Miami, 96 (ill.), 97 (ill.), 102; coral heads and pinnacle rocks, 93

Flowerfield, Mich., 52 (ill.), 53 (map)

Forests, 23

Gardens, 12

Genesee River, opp. 74 (ill. and map)

Geologic maps, 69

Geology, 69

Glacial drift plain, 52 (ill.) 55

Glaciers, 57; glacial gorge, Mt. Shasta, 59 (ill.); Mt. Shasta, 58 (ill.)

Gloucester Point, Va., 77, 83

Goddard, G. W., 72

Gorges, 57, 61; Genesee River, opp. 74. (ill. and map); glacial gorge on Mt. Shasta, 59 (ill.); San Joaquin Hills, California, 68 (ill.); Yosemite Valley, 60 (ill.)

Grand Trunk Railway, near Schoolcraft, Mich., 56 (ill.)

Great Plains, 50; river channel--Red River, 51 (ill.)

Gwynn Island, Virginia, 46 (ill.), 47 (map)

Half Dome, 60 (ill.)

Hampton, Va., small stream near, 33 (ill.)

Headward erosion, 57, 65 (ill.), 68 (ill.)

Hell Gate Bridge, 11, 15 (ill.)

Hereford Inlet, New Jersey, 98 (ill.)

Hill Marsh, Virginia, 34 (ill.), 35 (map), 38

Hooks. _See under_ Spits

Hotlum Glacier, Mt. Shasta, 58 (ill.), 59

Hudson River and West Point, 8 (ill.)

Ice cap, 57

Inclinometer, 2, 3 (ill.)

Index map showing areas photographed, 75

Inlets, formation through barrier beach, 81 (ill.); Hereford Inlet, New Jersey, 98 (ill.); River, New Jersey, 82 (ill.); tidal--Beach Haven, N. J., 85 (ill.)

Introduction, ix

Iroquois, Lake, opp. 74

Islands, tied, 77 (ill.); at Napatree Point, Rhode Island, 92 (ill.)

Ives, H. E., 6, 79

James River and Mulberry Island, 24 (ill.), 25 (map)

Jones, E. Lester, 74, 88

Jones, John Paul, 7; mausoleum, 9 (ill.)

Kenilworth, D. C., 13

Kettleholes, 52 (ill.), 53 (map), 55, 56 (ill.)

Kilmarnock, Va., topographic sheet, 47

Lambs Creek, Virginia, 48 (ill.)

Land forms, submerged, 45

Landscape gardeners, 1, 11

Landscape gardening, 11, 12 (ill.), 13 (ill.); Long Branch, N. J., 18 (ill.)

Langley, S. P., ix

Langley Field, xi

Lassen Peak, 57, 62 (ill.), 63 (map)

Lassen Peak, Cal., topographic sheet, 63

Lava, 62

Lee, Robert E., statue, 12 (ill.)

Lee Marsh, Virginia, 36 (ill.); details, 30 (ill.)

Library of Congress, 7

Little Egg Harbor, New Jersey, 81, 85

Little Egg Inlet, New Jersey, 86 (ill.), 87, 91 (ill.)

Little Hell Gate, 15 (ill.)

Long Beach, Long Island, 100 (ill.)

Long Beach, New Jersey, 84 (ill.), 85

Long Branch, N. J., part, showing barrier beach development, 18 (ill.)

Long Island, East Rockaway Inlet, 100 (ill.); Far Rockaway bars, channels, beaches, and marsh, 100 (ill.); Rockaway Beach, 11, 17 (ill.); Hell Gate Bridge to, 15 (ill.)

Los Angeles, 79; map of region between Santa Monica and, 67

Lower Cedar Point, Maryland, 87 (ill.)

Ludlam Beach, New Jersey, 28 (ill.)

Map, index of photographed areas, 75

Mapping, city, 79; from the air, 72

Mapping camera, opp. 22; experiment with, 53, 56

Maps, air mapping and, 74; air photograph adjustment, 35; use of air photographs in revising, 79

Marsh drainage, 27, 29

Marshes, 27; Chesapeake Bay, difficult to chart, 76 (ill.); details of drainage, 30 (ill.); details of frequently submerged, 31 (ill.); Far Rockaway, Long Island, 100 (ill.); salt marsh areas of coastal plain, 32 (ill.); salt marsh features, 92; stream development in tidal marsh, 28 (ill.)

Mathews, Va., topographic sheet, 47

Mattaponi River, 29, 36, 38

Meanders, 33 (ill.), 38; abandoned, 50; Chattahoochee River, opp. 50 (ill. and map); marsh, 27

Menoher, C. T., xi

Mexican border, 71

Miami, Fla, channels and shoals, 96 (ill.), 102; dredged channel, 97 (ill.), 102

Michigan, glacial drift plain, 52 (ill.), 53 (map)

Military Academy. _See_ United States Military Academy

Military observation, 4, 6

Mjöberg, Eric, 71

Monument Avenue, Richmond, Va., 12 (ill.)

Moraines, 52 (ill.), 53 (map), 55, 57; Mt. Shasta, 59 (ill.)

Mosaics, 12, 20, 22 (ill.); Anacostia River, D. C., land along, opp. 22 (Fig. 13); Columbus, Ga., opp. 26 (Fig. 17); Mulberry Island, Virginia, 24 (ill.); Rochester, N. Y., opp. 74 (ill. and map)

Mountains, 22, 27; features, 57; of volcanic origin--Cinder Cone, etc., California, 62 (ill.), 63 (map)

Mud flats, 36; coastal, 41; stream channels and, 42 (ill.), 43 (ill.)

Mulberry Island, Virginia, 24 (ill.), 25 (map)

Mumfort Islands, Virginia, 77

Muskrats, 29, 39

Napatree Point, Rhode Island, 92 (ill.)

Naval Academy. _See_ United States Naval Academy

New angles, 7

New Guinea, 7

New Kent, Va., topographic sheet, 27, 35, 37

New Point Comfort, spit, 90 (ill.)

New York Connecting Railroad Bridge. _See_ Hell Gate Bridge

New York Harbor, xi

Newport News, Va., xi, 11; shipyards, 14 (ill.)

Oblique photographs, 1

Ocean City, N. J., 32 (ill.); hook, 89 (ill.)

Oil, prospecting for, 71

Ores, 69

Orientation, 61

Oxbows, 33 (ill.), 50

Pamunkey River, 29, 36, 38; Cousaic Marsh, 31 (ill.); Eltham Marsh, 36 (ill.), 37 (map): marshes, 27; Sweet Hall Marsh, 34 (ill.), 35 (map)

Panchromatic film, opp. 74

Paris, mapping, 79

Pecos River, 70 (ill.)

Pennsylvania Avenue Bridge, 13, opp. 22 (ill. and map)

Perry, Commodore, 72

Photographs, mosaic. _See_ Mosaics

Photography, airplane. _See_ Air photography

Piankatank River, Virginia, drowned terraces at mouth, 46 (ills.)

Pictures from new angles, 7

Plains, glacial drift, 55; glacial drift, Michigan, 52 (ill.), 53 (map); photographing from the air, 50

Popes Creek, Virginia, 83 (ill.)

Poquoson River, Virginia, 76, 94 (ill.)

Port Clinton, Ohio, 72, 73 (ill. and map)

Potomac Park, Washington, D. C., 16 (ill.)

Potomac River, xi, 16 (ill.); channels, tributary, 101; Lower Cedar Point, spit, 87 (ill.); Popes Creek and, 83 (ill.); Powells Creek and, 93 (ill.); Quantico Creek and, 95

Potter, Lieutenant, opp. 74

Powells Creek, Virginia, 93 (ill.), 101

Put-in-Bay, 72, 73 (ill. and map)

Quantico Bay, 95 (ill.)

Quantico Creek, 95 (ill.)

Rahbeg, Arabia, 101

Railroads, 23

Randalls Island, 15 (ill.)

Ray filter, 102

Reconnaissance work, 69, 71

Red River, Texas-Oklahoma, 50, 51 (ill.)

Relief, means for showing, 5; representation on maps, 66

Revision of maps, 79

Richmond, Va., Monument Ave., etc., 12 (ill.)

Rivers, 22; Plains--Red River, 50; miniature system, 33 (ill.)

Roads, 23

Roberts Creek, Virginia, 94 (ill.)

Rochester, N. Y., 2, opp. 74 (ill. and map)

Rochester, N. Y., topographic sheet, opp. 74

Rockaway Beach, Long Island, 11; part, showing development, 17 (ill.)

Rocks, Florida coast experiment, 93; sedimentary, 69, 70 (ill.); study of, 69

Royal Arches, California, 60 (ill.)

San Joaquin Hills, California, 68 (ill.)

Sand bars, 45, 46 (ill.); Cape Charles, Virginia, 99 (ill.); Far Rockaway, Long Island, 100 (ill.)

Sandy Hook, N. J., 78 (ill.)

Santa Monica, Cal., 65, 66; map of region between Los Angeles and, 67

Santa Monica Mountains, 57, 66 (ill.), 67 (map)

Santa Monica, Cal., topographic sheet, 67, 79

Scale in vertical photographs, viii, 74

Schoolcraft, Mich., 54 (ill.), 55 (map), 56, 72; kettleholes near, 56 (ill.)

Schoolcraft, Mich., topographic sheet, 53, 55

Seashore, 22

Sedge grass, 29, 30, 38

Sentinel Rock, 60 (ill.)

Sepulveda Canyon, California, 66 (ill.), 67 (map)

Sevenmile Beach, New Jersey, spit and shoal, 98 (ill.)

Severn River, Virginia, 7, 9 (ill.)

Shadows, 5, 61

Shark River Inlet, New Jersey, 82 (ill.)

Shasta, Mt., 57, 58 (ill.); glacial gorge on, 59 (ill.)

Shipyards, 11; Newport News, 14 (ill.)

Shoals, 45, 84 (ill.), 85, 94 (ill.); Hereford Inlet, New Jersey, 98 (ill.); Miami, Fla., 96 (ill.), 97 (ill.), 102

Shore features, 83

Shrubbery, 13 (ill.)

Sierra Nevada Mountains, Cal., 62 (ill.), 63 (map)

Silt, 29, 36, 39

Simi Hills, California, 65 (ill.)

Simons, J. W., Jr., xi

Sky, cloudy and overcast, 49

Spa Creek, Maryland, 7, 9 (ill.)

Spits, lines of growth, Tucker Beach, New Jersey, 91 (ill.); recurved, 88 (ill.), 89 (ill.), 90 (ill.); Sevenmile Beach, New Jersey, 98 (ill.); simple spit, 87 (ill.)

State-War-Navy Building, Washington, D. C., 16 (ill.)

Stereoscopic camera, 6

Stevens, A. W., opp. 74, 89

Stone Canyon, California, 66 (ill.), 67 (map)

Stonington, Conn., 92

Stove Point Neck, Virginia, 46 (ill.), 47 (map)

Stream channels and mud flats, 41, 42 (ill.)

Streams, development in tidal marsh, 28 (ill.) _See also_ Rivers

Submarine geography, 45

Submarines, 101

Submerged land forms, 45

Submerged objects, detection, 101

Sunken mines, 101

Sunlight, 49

Surface, general aspects as seen from the air, 22

Swamps, 27

Sweet Hall Marsh, Virginia, 34 (ill.), 35 (map), 39

Swiss school of hill shading, 66

Terraces, underwater, 15, 94 (ill.)

Texas-Oklahoma boundary, 51 (ill.)

Thomas, H. H., 101

Thoroughfares, 34 (ill.), 35 (map), 39; Eltham Marsh, 36 (ill.)

Tidal Basin, Washington, D. C., 16 (ill.)

Tidal deltas, 82 (ill.), 83 (ill.); Barnegat Inlet, 84 (ill.), 85

Tidal inlet, Beach Haven, N. J., 85 (ill.)

Tidal marshes, stream development, 28 (ill.)

Tied island, 77 (ill.); development--Napatree Point, Rhode Island, 92 (ill.)

Tombolos, 92 (ill.)

Topographic mapping, 72

Treasury Building, Washington, D. C., 16 (ill.)

Trees, 13 (ill.)

Tucker Beach, New Jersey, spit, 91 (ill.)

Underwater topography, 45; best conditions for photographing, 47; channel in Quantico Bay, 95 (ill.); channels (natural) at Miami, Fla., 96 (ill.), 102; channels, shoals, terraces--Roberts Creek, Virginia, 94 (ill.); Chesapeake Bay, 90 (ill.)

United States Army Air Service, viii, xi, xii

United States Coast and Geodetic Survey, 74; coast line charting, 87, 88; Florida coast experiment, 93

United States Geological Survey, co-operation, xii

United States Land Office, 56

United States Military Academy, 8 (ill.)

United States Naval Academy, 7, 9 (ill.)

United States Naval Observatory, 13 (ill.)

United States Navy Air Service, viii, xi, xii

Vertical photographs, 1; scale, viii, 74; horizontal control, 74

Viewpoint, 1

Village, prototype, 54 (ill.)

Virginia, Eastern Shore mud-flat area, stream system, 41, 42 (ill.), 43 (ill.); tidewater portion, 38

Visibility under water, 102

Volcanic craters. _See_ Craters

Volmat, J., 99, 101

War and Navy offices, new, Washington, D. C., 16 (ill.)

Wards Island, 15 (ill.)

Warwick Creek and Mulberry Island, Virginia, 24 (ill.), 25 (map)

Washington, D. C., Capitol, frontispiece, 7; Library of Congress, 7; mapping, 79; part showing White House, Treasury, and many familiar features, 16 (ill.); topographic map, part, opp. 22; United States Naval Observatory, 13 (ill.)

Washington Column, California, 60 (ill.)

Washington Monument, 16 (ill.)

Wash-overs, 81 (ill.), 86 (ill.)

Watch Hill, R. I., 92

Water, Visibility under, 102

West Point, N. Y., United States Military Academy at, 2, 8 (ill.)

West Point, Va., 36 (ill.), 38; marshes, 29, 30 (ill.)

White House, Washington, D. C., 16 (ill.)

Wichita Falls, Tex., 51

Wildwood, N. J., 98

Wintun Glacier, 58 (ill.)

Wright, Orville, ix

Wright, Wilbur, ix

York River, 38, 76, 83, 87; shoreline, 77 (ill.)

Yosemite and Mt. Lyell topographic sheets, 61

Yosemite Valley, 60 (ill.), 61 (map)

FOOTNOTES:

[1] Cf. his The Use of the Panoramic Camera in Topographic Surveying, With Notes on the Application of Photogrammetry to Aerial Surveys, _U. S. Geol. Surrey Bull. 657_, Washington, D. C., 1917.

[2] H. E. Ives: Airplane Photography, Philadelphia, 1920, pp. 328-350.

[3] The Pamunkey gets its name from a tribe of Indians famous in the early days of Virginian history but now reduced to a few families living on a reservation situated on the banks of the river near Lester Manor. Mattaponi is a combination name. The Mat and the Ta unite to form Matta Creek. The Matta and the Po unite, and Ny Creek is a tributary to the Po. The waters of these streams unite to form the river, and the names Mat, Ta, Po, and Ny unite to form its name--Mattaponi.

[4] A. H. Brooks, personal communication.

[5] Eric Mjöberg: A Proposed Aërial Expedition for the Exploration of the Unknown Interior of New Guinea, _Geogr. Rev._, Vol. 3, 1917, pp. 89-106.

[6] The Use of Aerial Photographs in Topographic Mapping: A Report of the Committee on Photographic Surveying of the Board of Surveys and Maps of the Federal Government, 1920, _Air Service Information Circular (Aviation) No. 184_, War Department, Washington, D. C., 1921.

[7] What can be done, however, by photographing obliquely from a high altitude, thereby increasing the area in the field of vision, is illustrated by Figure 54, which encompasses Lake Erie from one shore to the other and, in its representation of the main features of the region, is akin to maps on a relatively small scale, such as 1:1,000,000.

[8] J. W. Bagley: The Use of the Panoramic Camera in Topographic Surveying, With Notes on the Application of Photogrammetry to Aerial Surveys, _U. S. Geol. Survey Bull. 657_, p. 84. “The scale of the photograph is given by the relation _f_/H, _f_ being the focal length of the lens and H the height of the camera above ground.” (_Ibid._)

[9] E. Lester Jones: The Aeroplane in Surveying and Mapping, _Flying_, June, 1919, pp. 438-441, 472, and 476.

[10] H. E. Ives: Airplane Photography, 1920, pp. 407-408.

[11] E. Lester Jones: Surveying From the Air, _Science_, Vol. 52, 1920 (Oct. 17), pp. 574-575, and _Engineering News-Record_, Dec. 16, 1920, pp. 1184-1186.

[12] E. Lester Jones, _op. cit._ (_Science_), p. 575.

[13] J. Volmat: Application de la photographie aérienne aux levés hydrographiques, _Comptes Rendus de l’Acad. des Sci. [de Paris]_, Vol. 169, 1919, Oct. 27, pp. 717-718; _idem_: Rapport sur la mission photohydrographique de Brest (1919), _Annales Hydrogr._ (publ. by Service Hydrographique de la Marine, Paris), 3rd Series, 1919-20, pp. 191-220, with seven air photographs and corresponding sections from French coast charts.

[14] H. Hamshaw Thomas: Geographical Reconnaissance by Aeroplane Photography, With Special Reference to the Work Done on the Palestine Front, _Geogr. Journ._, Vol. 55, 1920, pp. 349-376; reference on p. 369.