Vector data sets for Version 3.0 are distributed in ARC/INFO export (.e00) format. Some raster data sets from Version 1.0 (late 1980's) used in Version 3.0 are distributed in .e00 format as well. Data in SDTS format are available upon request. Some data sets are Shapefiles. Raster data used in Version 3.0 are distributed in ASCII (.txt) format.
Average data (*.mean) files are distributed in ASCII comma-delimited format. They represent average values by SPARROW watershed segments, Version 3.0. The first column is the unique reach identification number (E3RF1). The second column is the average value for that watershed.
All shapefiles and associated data are compressed in .zip files. All shapefiles were generated with the ARCSHAPE command.
Text (.txt) files representing raster data are ASCII files created from ARC/INFO GRIDASCII where xxx is a number, and the keyword nodata_value is optional and defaults to -9999. The end of each row is terminated with a carriage return in the file.
YLLCENTER xxx|YLLCORNER xxx
To load .txt Files representing raster data into ArcView,
1. Uncompress the file if it has a .zip extension (<filename>.zip)
2. Start Arcview GIS and be sure the Spatial Analyst extension is turned on. To do this, select File and Extensions... and check the Spatial Analyst.
3. Open existing or start a new project. Open and/or make a View active.
4. Import the gridded ASCII file you by selecting File and then Import Grids. The Import File Type should be set to ASCII.
5. In the Import ASCII Files dialog box, change the "List Files of Type" to All Files (*.*). Select the unzipped ASCII file.
6. At this point you must provide Arcview GIS with an output file name (the default is imgrd1) for the imported grid. Be sure you are saving in the correct directory and then type in the filename.
7. At the dialog box "Import Grids: ..." Cell values as integers? Select "yes."
8. Now go to a View, and add a theme. In the Add Theme dialog box, change type of theme from Featured Data Source to Gridded Data Source. Then simply select the imported grid that you saved in step 6.
Return to report -- Digital Data Used to Relate Nutrient Inputs to Water Quality in the Chesapeake Bay, Version 3.0
Maintainer: John Brakebill firstname.lastname@example.org
Last modified: 12/30/04