should, whenever aircraft are available, supplement their observations by a bird's-eye-view of the region in which their work lies.

"The most evident opportunity for the practical use of aircraft in the commercial fisheries at the present time, lies in their employment as scouts for the purse-seine fishermen, in the pursuit of such species as menhaden, mackerel, bluefish, kyacks and other schooling fish. In the case of the spring mackerel fishery it is believed that the use of aircraft would save much time in locating the fish upon their first appearance, and in enabling the fishermen to keep in touch with the fish as they appeared further north. The chief service rendered would be notification of the fishermen of the general vicinity of the schools, and it would require actual trial and practice to determine how much could be done in directing fishing vessels to particular schools by means of radio-telephone or other methods of signaling. It would appear that the menhaden fishery offers the most promising field for experiment in this direction.

The benefit to the fishing fleet would be in time and fuel saved in the search of fish, and the concentration of effort on large schools instead of wasting time on small, scattered bunches of fish. It is quite possible also that schools of large fat fish might be distinguished from those of smaller, leaner fish, although this would require experience in observation. Another field for experiment would lie in the guidance of fishing steamers to large schools not visible from the crosstrees, but plainly visible from aircraft, and communication by means of wireless telephone, marking buoys, or other devices, which would enable the boats to set the seine around the, to them, invisible fish. Such co-operation would be of great advantage to the Naval Air Service, as well as to the fishing interests, as it would provide for the naval aviators excellent practice in scouting, station finding, and communications."

AIRCRAFT IN SEAL HUNTING

The successful use of aircraft in fisheries turns attention to kindred pursuits. The Newfoundland Government expected, early in 1921, to have aircraft in operation in connection with the sealing fleets of the north. The theory of operation is this: The aerial observer will spot a herd of seal. The machine then descends to the ice and the hunters make their kill. The pelts are stacked on the "ice pans," to be picked up by surface ships when navigation is possible. The pelt stacks are located from the air and collection thus facilitated. It has been demonstrated that it is possible for a seaplane to alight on or take off from a snow field (see Aeromarine report in Chronology) and this proof is believed to be of peculiar significance in estimating future usefulness of aircraft in the Arctic.

LIFE SAVING AT SEA

Utilization of aircraft in Coast Guard work, which had been planned as far back as 1916, but which had been delayed by the war, was brought about finally in the month of September, 1920, when four H. S.-2-L seaplanes began operations at Morehead City, N. C.

Up to the time this volume went to press much experimental work had been accomplished, demonstrating to the satisfaction of the Coast Guard that aircraft would unquestionably provide great assistance along the following lines:

1. Saving life along the coast and at sea contiguous to the coast. 2. Saving property along the coast and at sea contiguous to the

coast.

3. Enforcement of customs laws.

4. Transporting Government officials where time is the important element or where other means of conveyance fail.

5. Fisheries patrol, assisting commercial fleets along North Carolina Coast.

6. Reconnaissance of water and land areas in surveying, mapping, etc., especially in connection with Coast Guard communication system.

The Coast Guard is indebted to Naval Aviation for the training of its personnel and use of equipment. The Navy has turned over to the Coast Guard a number of surplus seaplanes from the abandoned air station at Morehead, N. C. The State of North Carolina has placed at the disposal of the Guard, at nominal cost, a part of the tract of land once comprising the station.

The area within the radius of operations of the aviation station at Morehead City extends from Cape Henry on the north to Cape Romaine on the south and to a distance offshore of about one hundred miles. The location of the first station is particularly fortunate in that it is at a point 68 nautical miles from Cape Hatteras, 13 nautical miles from Cape Lookout and 80 nautical miles from Cape Fear, the coast line between these points comprising one of the worst stretches of our coasts in point of number of marine disasters occurring on or off the coast. It is also an extent of coast line and inland waterway peculiarly inaccessible for officers of the service engaged in inspection and construction of beach units of the service and in the maintenance of the communication system.

In the saving of life at sea by aircraft, the Coast Guard reports actual rescues of persons in the water. Instances have arisen when boats have foundered within sight of the Guard, but distance precluded rescue by surface boat. Then it was that the seaplane, at

home equally on the water as in the air, flew swiftly with succor. The commanding officer of the Morehead Station states that he has arranged for the reporting of accidents and that he has two planes ready for emergency use.

It is fully expected that seaplanes will, on the first opportunity, be the means of saving life by contributing to the location of vessels in distress, first by scouting, second by radio or direct report, and, third, by carrying means of relief. "In some cases," the Coast Guard reports, "should it prove impracticable to get a line to a vessel by means of the beach gun, aircraft properly equipped might effect the purpose desired. To this end design of gear has been developed and the tests to prove its practicability or to develop it further will be undertaken shortly."

The Coast Guard is particularly impressed with the assistance aircraft provide in searching for derelicts when the object of the search is within a reasonable distance of the coast. The commanding officer of the aviation station would make arrangements with the commanding officer of cutters at nearby ports so as to be able to assist them effectively in searches. The recovery of derelicts under these conditions and their return to their owners as well as their elimination as dangers to navigation can well be classed as saving property."

The duties of the Coast Guard in the prevention of smuggling and the relation of aircraft thereto are dealt with in the Appendix.

CHAPTER VI

AERIAL PHOTOGRAPHY-ITS USES IN SURVEYING, MAP MAKING, EXPLORATION, CITY PLANNNG, ETC.; HOW AERIAL MAPS ARE MADE

A

ERIAL photography has been one of the richest contributors to the development of useful activities for aircraft.

So successful have been experiments conducted by the U. S. Coast and Geodetic Survey, during 1919 and 1920, that it is planned, with the assistance of the U. S. Air Service, Naval Aviation and private operators, to revise, by means of aerial photography, the entire American shore line of existing charts of the Atlantic and Pacific Oceans.

The aerial camera, during 1920, occupied an important part in laying out commercial, postal and military routes over the United States and to Alaska; in making preliminary surveys of little known regions in our island possessions; in locating railroad rights of way at far less expense and in a fraction of the time once required; in exploration of Arctic and Antarctic regions, accomplishing in days what once would have occupied years; in urban uses, such as city planning, rail and water terminal improvements, real estate exploitation, fire insurance classification and the correction of congestion evils; and, finally, in what is proving to be a most attractive and lucrative branch - the addition to art of beautiful views which could be obtained in no other way than from the air.

A HERITAGE FROM THE WAR

It was the war which revealed somewhat the possibilities of aerial photography. Aircraft operating under Brig. Gen. William Mitchell, commander of American air forces at the front in France, frequently carried on photographic observation at 25,000 feet. Since the Armistice, equipment has been so improved that work is possible at 30,000 feet. But important as was the part taken by aerial photography in the war, General Mitchell sees even greater opportunities in peace. "The most important element in the development of a country," he writes, "is to have a good map of the country concerned, which will show how roads, railroads, paths, canals, or anything necessary

for communications can be established through it. In the United States, less than 40 per cent of our area has adequate maps. In this country there is no way by which mapping can be completed of the whole area for many years except from the air, and with the proper distribution of aerial mapping facilities throughout the country we will be able to map everything necessary within three years."

WORK BY U. S. COAST AND GEODETIC SURVEY

The first topographical experiments with aircraft were made by the Coast and Geodetic Survey in the summer of 1919. In June and July of that year, at the request of the Survey, photographs of Atlantic City were taken from Air Service planes. This area was selected because it is characteristic of much of the Atlantic coast line. Though experimental in character, the work was of such value that the results are now being utilized to revise existing charts of the New Jersey shore.

The photographs were taken from an altitude of 7,000 feet, from a "K-1" mapping camera, using a lens of 10-inch focal length. The individual photographs were then assembled into a mosaic over a rough control scheme. Study of these photographs by members of the Survey, according to a special report prepared for this review, revealed interesting possibilities in revision, especially along those sections of the Atlantic coast where the shore line is frequently changed by action of the sea.

During the same period, Naval Aviation, at its Key West station, investigated the possibilities of aerial photography as an aid to hydrographic surveying.

In March, 1920, a single strip of photographs along the outer coast of New Jersey was made for chart revision by the Air Service from an altitude of 10,000 feet, using a “K-1" camera with a 300 mm. lens.

There are two methods, the Survey writes, used in reducing the photographs to chart form. A strip mosaic limited to ten photographs is assembled. This is compared with the latest topographic sheet of the area and if no discrepancies appear between control points, a tracing is made of the features wanted on the chart and this tracing is reduced photographically to scale. The second method differs in that, if discrepancies appear when the mosaic is compared with the sheet, a reduced photograph is made of the mosaic on the same scale as the topographic sheet. A direct comparison can then be made to locate the cause of error. The reduced photograph is then treated as an ordinary survey, and adjusted to the nearest control points.