1. ZGRID1 . 



ZGRIDl sometimes gives poor results near a land-water boundary or an outer 

 computational boundary where there are too few irregularly spaced raw data 

 points. Where there is a significant topographic trend, ZGRID1 can also give 

 misleading results if the number of raw data points is too small. 



2. CONTOR . 



When a bathymetric feature has a size comparable to the grid spacing, con- 

 tours which go near or through the feature may cross or have unrealistic loops 

 or wiggles. To minimize this contour "noise," the regularly spaced depth or 

 bed elevations produced by ZGRIDl may have to be smoothed. 



VI . SUMMARY 



This report gives general descriptions of products from two computer pro- 

 grams (ZGRIDl and CONTOR) which process digital bathymetric data. ZGRIDl gen- 

 erates regularly spaced bathymetric data from irregularly spaced data, and 

 CONTOR uses regularly spaced data to determine and draw contours. A large set 

 of bathymetric data available on magnetic tape for U.S. coastal regions is 

 also described. Examples of program output are presented for two areas, one 

 near Great Egg Harbor Inlet and the other near CERC's FRF. 



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