SURVEYING IN HAZE AND FOG 



The Field Research Group of the Beach Erosion Board has been 

 conducting littoral drift studies on the coast of California at 

 Anaheim and Santa Monica Bays. Throughout the conduct of these 

 investigations it was necessary to follow a strict schedule for 

 hydrographic survey operations in order to meet the work schedule. 

 Standard survey methods employed by this group had to be modified 

 in order to permit operations during periods of poor visibility 

 created by haze and fog. Several expedients which would increase 

 the range of visibility of the instrument-men were tried, but 

 only one method showed enough promise to warrant its continued use. 

 This entailed the installation on the sounding craft of a high 

 intensity mercury vapor lamp that would be visible from shore 

 during the frequent periods of haze and fog. 



This equipment consisted of a 220 volt, 60 cycle, 1600 lumen 

 mercury vapor lamp with a 4.00 volt-ampere, 110-220 volt autotrans-^ 

 former. A 1-J kilovolt-ampere generator, driven by a gasoline engine, 

 was provided as the source of power for the lamp. The sounding 

 craft on which the installation was made was an Army 2-|-ton amphibian 

 truck (commonly known as a rt Duck M ). Accompanying photographs show 

 the location of this equipment aboard the "Duck." Reasonable protection, 

 such as a canvas tarpaulin, had to be provided for the transformer 

 and generator to shield it from salt water spray. The lamp itself 

 required no additional protection as it is constructed of two concentric 

 pyrex tubes, the outer tube protecting the hot inner tube from breaking 

 due to contact with sea spray. 



This equipment, exclusive of the generator unit, can be procured 

 and installed for a cost outlay of about $50.00. If a suitable power 

 source is not available on the sounding craft, a portable generator 

 unit similar to the one described in this article can be bought for 

 about $350.00. 



When the apparatus was installed, a number of tests were made 

 which showed that the use of the lamp increased the range of working 

 visibility by fifty to seventy-five percent. The Field Research Group 

 of the Beach Erosion Board has used the equipment during hydrographic 

 survey operations extending over a period of several months, and 

 during this period it is estimated that time lost due to haze and fog 

 has been reduced by fifty percent. 



