Table 3-2. Estimates of potential error associated with shoreline position surveys. 



Traditional Engineering Field Surveys (1875/79) 



Location of rodded points 



Location of plane table 



Interpretation of high-water shoreline position at rodded 



points 

 Error because of sketching between rodded points 



±3 ft 

 ±6 to 10 ft 

 ±10 to 13 ft 



up to ±16 ft 



Cartographic Errors (all maps for this study) 



Map Scale 



1:10,000 



1:20,000 



Inaccurate location of control points on map relative to 



true field location 



Placement of shoreline on map 



Line width for representing shoreline 



Digitizer error 



Operator error 



up to ±10 ft 

 ±16 ft 

 ±10 ft 



±3 ft 



±3 ft 



up to ±20 ft 

 ±33 ft 

 ±20 ft 

 ±6 ft 

 ±6 ft 



Aerial Surveys (1928, 1948, and 1970 shorelines) 



Map Scale 



1:10,000 



1:20,000 



Delineating high-water shoreline position 



±16 ft 



±33 ft 



GPS Survey (1996 shoreline) 



Delineating high-water shoreline 

 Position of measured points 



±3 to 10 ft 

 ±6 to 16 ft (specified); ±3 to 10 ft (field tests) 



Sources: Shalowitz 1964; Ellis 1978; Kruczynski and Lange 1990; Anders and Byrnes 1991; 

 Crowell, Leatherman, and Buckley 1991 



Table 3-3. Maximum potential rms error for shoreline change data. 



Date 



1928 



1948 



1970 



1996 



1 875/79 



±74.5 1 



±74.5 



±56.9 



±52.0 



(±1.5)* 



(±1.0) 



(±0.6) 



(±0.4) 



1928 





±78.1 



±61.5 



±56.9 





(±3.9) 



(±1.5) 



(±0.8) 



1948 







±61.5 



±56.9 







(±2.8) 



(±1.2) 



1970 









±30.5 









(±1.1) 



Magnitude of potential error associated with high-water shoreline position 



change (ft). 



Rate of potential error associated with high-water shoreline position change 



(ft/year). 



Chapter 3 Assessment of Coastal Change 



3-3 



