- Author
-
Collins, B. L.
|
Sanders, P. A.
- Title
- Evaluation of the Visibility of Buoys and Topmarks.
- Coporate
- National Institute of Standards and Technology, Gaithersburg, MD
- Sponsor
- Coast Guard, Croton, CT
- Report
-
NISTIR 4756
March 1992
76 p.
- Distribution
- Available from National Technical Information Service
- Keywords
-
buoy
|
topmarks
|
visibility
|
color
|
detection
|
lighting equipment
|
navigation aid
|
shape
- Abstract
- The research literature on the visibility of colors and topmarks used to code information on buoys and other aids to navigation was reviewed. Although several studies suggest that color may be recognizable at greater distances than topmarks, it is difficult to draw conclusions about the relative effectiveness of different topmark, color, and buoy configurations because the researchers used small numbers of observers and tested different aspects of aids to navigation. Consequently, two experiments were conducted to determine the distance at which buoy topmark configurations could be correctly identified for different lighting geometries and background conditions. In experiment 1, the visibility of buoys and topmarks as separate entities was evaluated for ten different buoy configurations in simulated waterway viewing environments. Four buoys, including safe water, danger, port and starborad, were shown with and without topmarks, while two buoys, north and east, always had topmarks. Front and back lighted buoys were presented against both water and foliage, as well an in a "twilight" condition. In experiment 2 the visibility of buoys with integral topmarks was evaluated for front lighting conditions only. Analysis of the data from both experiments strongly suggests that topmarks did not increase the visibility the buoy configurations studied. It appears that the topmark is too small to be effective beyond 0.8 km (0.5 mile) - near the limit of visual resolution. The data indicated that color is a critical cue in determining buoy type, with significant differences in buoy detectability between red and green buoys. Front lighting also increased visibility distance significantly. Even under back lighting conditions, however, the presence of a topmark did not increase buoy visibility. While it is possible that training could have improved accuracy, its effects would likely be limited to distances shorter than 0.8 km (0.5 miles).