CREATING A TIN The shapefile was exported into a coverage using ArcCatalog. The point coverage was converted to a TIN using ArcToolbox using the "Create a tin" wizard with the following constraints: A hardclip area, using a hull approximately the size of the bathymetric point footprint confined the processing area. Weed tolerance was set to 200; z-value = 1. The hull (footprint) was created by taking the ribay.shp file (<http://www.edc.uri.edu/rigis-spf/statewide/state.html#boundaries>) and stretching four of the southernmost vertices to contain all of the bathymetric points. This shapefile was then exported to a coverage in ArcInfo workstation using the SHAPEARC command (default options) and then building for polygons. "Hard erase" areas were created from boundaries available from the above Web site (statline.shp). The land area was created from the statline.shp file by converting that file to a coverage in ArcCatalog. The islands were created by taking the ribay.shp file and selecting all the polygons that were not equal to water, converting that subset to a shapefile in ArcView, exporting that new shapefile to a coverage in workstation ArcInfo using the SHAPEARC command (default options), and then BUILDing for polygons. Weed tolerance was set to 200; z-value = 1. The proximal tolerance was set to 10 with a z-factor of 1.
CREATING A GRID Using ArcToolbox, the tin was converted to a grid using the "Import tin to grid" tool. Cell size was set to 50 (feet). Using ArcView, Analysis Properties/Analysis Extent was set to the original point coverage with a cell size set as "current value." Map calcultor was employed to multiply the existing grid by 1. This removed some of the edges from the grid, which were of questionable accuracy because of the way that TIN handles edges. The new map calculation was saved (convert to grid). A new grid representing soundings in feet was calculated using the Map Calculator and a conversion factor of 3.280839895013123.