PHOTOGRAMMETRIC SURVEYS FOR NAUTICAL CHARTING 
USE OF COLOR AND INFRARED PHOTOGRAPHY 
by 
Captain L. W. Swanson 
Chief, Photogrammetry Division 
United States Coast and Geodetic Survey 
ABSTRACT: One of the prineipal functions of the Coast and 
Geodetic Survey is to provide nautical charts of the 2% mil- 
lion square miles of coastal waters of the United States and 
its possessions, and the Commonwealth of Puerto Rico.  Photo- 
grammetry has become a recognized method of production, 
maintenance, and revision for these charts. Our photogram- 
metric procedures have been developed over the last 30-odd 
years using nine-lens and single-lens photography to perform 
aerotriangulation, to prepare detalled large scale maps, and 
to correct the aids, landmarks, and land features. Our first 
color photography was taken two years ago and exceeded our 
expectations in the amount of detail available which could 
not be seen on panchromatic photography. The color photog- 
raphy is now used to locate aids to navigation, to position 
channels and shoals, rocks awash and slightly submerged 
rocks, and small inlets that shift and change with storms. 
We are looking forward to the time when color emulsions on 
low shrink film base and a means of making color diapositives 
wlll be available. The present plotting equipment is not 
satisfactory for use with the existing color transparencies. 
We are experimenting wlth improvements for our instruments 
to enable us to use the color transparencies and we have 
prepared black and white diapositives directly from the 
color transparencies for use on the Kelsh Plotter. Infrared 
photography 1s also in use to give us the strong contrast 
between water and land areas for more exact determination 
of shorelines. 
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