Lower Standard Parallel: 27 degrees, 30 minutes (27.5)
Upper Standard Parallel: 35 degrees (35.0)
False Easting: 1,500,000 meters
False Northing: 6,000,000 meters
Datum: North American Datum of 1983 (NAD83)
The DEMs were clipped by first converting a box theme (as digitized in ArcView around the study area) to a coverage using the ArcWorkstation command shapearc box boxcov. Then the boxcov coverage was processed using the ArcWorkstation build boxcov command. The cell size was set to that of the DEM (setcell grid), and the window to that of the box coverage (setwindow boxcov grid). The coverage was turned into a grid (temp = polygrid [boxcov]), set to one (temp2 = temp / temp) and then clipped (clpgrd = temp2 * dem30m).
Once the DEM was clipped, it was projected into the TCMS Albers projection. This was done in ArcWorkstation. Each DEM was processed as outlined under CRWR-PrePro in Chapter 3.
The development of a curve number (CN) grid was necessary to estimate the spatial variability of runoff from a rainfall event. After the DEMs were clipped, the same was done with the USGS Land Use/Land Cover (LULC) coverage and the USDA/NRCS STATSGO soils coverage for the same area. Figure 4.8 shows the Land Use/Land Cover data clipped to the area of interest.