- 3 = 
In this respect color photography is saving us time and 
money and giving us more up-to-date charts--it is already 
in general use in the Coast Survey as a supplement to our 
usual panchromatic mapping photography. 
We are using and beginning to use color photography: 
1. TO IDENTIFY AND TO LOCATE AIDS TO NAVIGATION. 
2. TO MAP THE TOPOGRAPHY OF UNEVEN BOTTOM IN SHOAL 
WATERS TO ASSIST THE HYDROGRAPHER IN DEVELOPING AND 
SWEEPING THESE AREAS. 
3. TO MAP ALONGSHORE ROCKS AWASH AND SLIGHT SUB- 
MERGED ROCKS IN PLACES WHERE THESE ARE CLOSE TO 
TRAFFIC LANES AND FOR ANY REASON DIFFICULT TO 
DEVELOP IN DETAIL BY SOUNDING. 
4. TO INVESTIGATE CHANGES IN SHORELINE AND EN- 
TRANCE CHANNELS AT INLETS AND FREQUENTLY TO RE- 
VISE THESE FEATURES. 
5. TO ASSIST THE COAST GUARD IN THE INVESTIGATION 
OF ACCIDENTS INVOLVING AIDS TO NAVIGATION REPORTED 
MISSING OR OUT OF POSITION. 
One of the principal uses of color aerial photography 
is to locate lights, day beacons and buoys moved by storms 
or collisions so that the charted positions can be corrected. 
The charts can also be kept up to date by showing cultural 
changes from the color photographs without the necessity 
of a field examination. 
The virtue of color photography is in the fact that it 
1s œwually possible to identify and locate the ald by office 
examination of the photographs and office plotting without a 
trip to the field. Formerly, we had to locate these by ground 
Survey, or visit the area to identify them on panchromatic 
photography, or target the aids prior to panchromatic photog- 
raphy, each a costly and time consuming task. 
As I mentioned before, there are some 40,000 aids-- 
most of them in the bays, harbors, and intracoastal waters-- 
and a large proportion of them subject to change:  BUOYS 
AND SINGLE PILE STRUCTURES ARE MOVED BY ICE, OR NOT TOO 
INFREQUENTLY, KNOCKED OUT BY PASSING VESSELS; AND CHANNELS 
AND SHOALS ARE CHANGED BY BOTH THE WORK OF MAN AND WEATHER.