574 



SCIENCE 



[N. S. Vol. LII. No. 1355 



China and India, the two most important 

 centers, national Museums of Natural His- 

 tory which would serve as centers of anthro- 

 pological, biological and geological investiga- 

 tion of the Far East. 



Ales Hrdlioka 

 U. S. National Museum 



SURVEYING FROM THE AIR 



The great possibilities of airplane pho- 

 tography in connection with the water and 

 land work of the Coast and Geodetic Survey 

 are looming up as a potential factor in ex- 

 pediting the mapping of our waterways and 

 interior surveys. This very important sub- 

 ject has been the object of careful study and 

 experiments by officers of the Survey, in 

 collaboration with the other branches of the 

 government, during the past year and the 

 rapid advance in aerial photography, first 

 seriously undertaken during the war, now 

 promises, with proper development, a method 

 of surveying that will probably far exceed ex- 

 pectations over the old methods in rapidity, 

 economy, and minuteness of detail. 



No little stress should be laid on the fact 

 that, not only are the possibilities good for 

 an early and complete revision of our shore 

 topography, but the opportunities that present 

 themselves for assisting materially in our 

 hydrographic work shouldn't be underesti- 

 mated. 



With the necessary facilitates and coopera- 

 tion supplied by the Army and Navy Aviation 

 Corps to the Coast and Geodetic Survey, ex- 

 perience has already proven the value of 

 aerial photography over the old method of 

 surveying in revision surveys of our coast 

 lines. 



This work so far, is divided into two 

 branches. Aerial Photo-Topography, and Aerial 

 Photo-Hydrography, and the results are shown 

 in the following recent practical demonstra- 

 tions : 



AERIAL PHOTO-TOPOGRAPHY 



In July, 1919, experiments were made at 

 Atlantic City, N. J., to ascertain the adapt- 

 ability of airplane photographs for use in 



topographic mapping. The area in the 

 vicinity at Atlantic City was chosen as it is 

 characteristic of so much of the coastal plain 

 territory of the Atlantic coast. This project 

 was essentially experimental in character, but 

 developed into one of practical value, as the 

 photographs are being used in a revision of 

 the charts of the New Jersey coast. 



This work was done in cooperation with 

 the Air Services of the Ai-my and Navy. 

 Both land and sea planes were used, and in 

 addition several photographs were made from 

 a dirigible. Three types of mapping cameras 

 were tried out, the "L" type, K-1, and Tri- 

 lens. An officer of the survey kept in close 

 touch with the work and furnished the groimd 

 control, constructing special targets in some 

 cases. 



A mosaic was constructed by members of 

 the Air Service of the Army, using the photo- 

 graphs made with the K-1 mapping camera. 

 These were taken at an altitude of Y,000 feet, 

 using a lens of 10 inch focal length, with a 

 resulting scale of about 1 :8,000. A rough 

 control scheme was first laid out, and the 

 mosaic constructed over this. 



This mosaic and also the individual photo- 

 graphs have been the subject of study by 

 engineers of the survey, especially with refer- 

 ence to control and interpretation. Various 

 methods of reduction for chart use were tried 

 out. A study was made of the accuracy of 

 mosaics and individual photographs. The 

 possibilities of control using the photographs 

 themselves to establish a graphic triangula- 

 tion, have been investigated. The most im- 

 portant point brought out from the study of 

 the results of the work at Atlantic City, was 

 the possibilities in revision work, especially 

 along those sections of the Atlantic coast 

 where the shoreline is subject to frequent 

 changes owing to the action of the sea. 



AERIAL PHOTO-HYDROGRAPHY 



At the same time that the experiments at 

 Atlantic City were being made, a distinct line 

 of investigation was being pursued at Key 

 West, Florida. Photographs were made by 

 the Naval Air Service to determine the pos- 



