Scale changes are accounted for by relating everything to the common scale 

 of the base map, reducing the inherent error involved in measuring distances 

 on two photos. Because important features are transferred to a base map, meas- 

 urements of features such as shoreline position can be made where required along 

 shore-normal lines, spaced as dictated by study needs and not by the reference 

 points on the aerial photos. This flexibility is useful in calculating shore- 

 line changes for an entire barrier island. 



Although the base map analysis technique involves steps not required in 

 the direct photo-measurement method, the technique may be worth the extra effort 

 in certain applications, e.g., sediment budget studies, projects that require 

 information on possible regions of longshore transport reversal, studies that 

 require the time-sequence construction and the plan view dimensions of coastal 

 structures, and possible requirements for information on the location and per- 

 sistence of longshore bars and inlet shoals. 



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