•IAN fEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC 



JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC 



Figure 8. Daily values of mean sea level at 

 Atlantic City, N.J., 1939. 



prepared for particular frequencies, usually M2 or K-, , have 

 cotidal lines connecting points of equal phase and co-range 

 lines connecting points of equal amplitude. Dietrich's 

 cotidal charts (Figures 9 and 10) show his empirical esti- 

 mates for diurnal and semidiurnal tides respectively based 

 on coastal and island observations. Projecting offshore is 

 clearly a subjective process and therefore cotidal charts 

 prepared by various oceanographers may vary significantly. 

 Actually, most coastal data are measured by tide gauges 

 located on piers within estuaries. Because the tide may be 

 significantly modified by the estuarine bathymetry, this is 

 the worst possible place to obtain data for projecting lines 



26-15 



