maps are being used aboard a ship, a must be 

 equated to Va-m^+c/, where 0-^ is taken from the 

 position error diagi-am, and o-j is computed by 

 dividing the first three terms on the right-liand 

 side of equation 2 by Vg-\-'g-, for the area in which 

 the ship is working, and then taking the square 

 root of the quotient. 

 Distribution of the Map Errors 



The standard deviations of the isobath depth 

 error (fig. 2) generally increase in an offshore 

 direction. Most of this increase is due to the steeper 

 topographic slope on the outer shelf and upper 

 slope which makes interpolation of depths between 



soundings less certain in these regions. A part of 

 the increase is also due to a wider spacing between 

 tracklines offshore. 



Most of the large inshore standard deviations 

 are also caused by locally steep topographic 

 slopes (e.g., the Hudson Channel, Long Island 

 Sound, Delaware Bay, and Nantucket Shoals); 

 however, the large deviations east of Cape Cod 

 are due both to wide trackline spacing and to steep 

 slopes. 



Figure 4 shows the percentage of the total vari- 

 ance of the dejjth error which can be attributed to 

 observational, positional, and interpolation errors. 



BATHYMETRIC MAPS AND GEOMORPHOLOGY OF MIDDLE ATLANTIC CONTINENTAL SHELF 



47 



379-242 O - 70 - 4 



