10.5 Shapefiles and ArcExplorer




Before we continue with the example from the previous section, insure that ESRI's software ArcExplorer has been installed. Other GIS programs, such as Map Window GIS could also be used. Using GIS software, it is possible to overlay multiple products, such as trajectories, concentration plumes, meteorological data contours, and even point data, all on the same display.

  1. In the previous section, we had already computed the 3-hr average concentration pattern from 03-06 UTC on the 26th. Open the Concentration / Display / Concentration / Contours menu and set the ESRI Generate radio-button. Execute will open the display and also create two ASCII text files, GIS_00100_ps_00.txt (and .att), in generate format. The file name changes slightly according to the time period and output layer. The .txt file contains the contour polygon points and .att file contains optional attribute information.

  2. The next step is to convert the Generate format files to the binary shapefile format. Press the Utilities / GIS to Shapefile menu tab to open the conversion menu. Use the browse button to find the GIS text file then select the polygons radio-button for the conversion method (polygons are closed lines). Because an attributes file is available, select the concentration radio-button. Press Process Data and four output files will be created (concplot.shp .shx .dbf .prj) in the working directory. A system message will be displayed when the conversion is complete.

  3. Open Arc Explorer and select the Add Layer icon to browse and select the concplot polygon file in the working directory. To add a map background file go to the \Tutorial\maps directory and select the states polygon file. As each layer is added it will appear on the left panel. Click the checkbox to display each layer. The concentration contours are below the states, therefore select the concentration box and drag it to the top of the column to show the plume on top of the state maps.

  4. To fix the colors and transparency, double-click the left panel states box and select the transparent fill option. Next double-click on the concplot box and change the Draw Features option to unique symbols. Double-click on the contour colors to customize, then after some panning and zooming the final display graphic will show something very similar to previous displays.

  5. Note that the above procedures may be different depending upon the version of ArcExplorer.

The ESRI ArcExplorer option provides a powerful display tool that can be used to overlay a variety of different products on the same map. The sample shapefiles on the CD were all obtained from public sources. As an alternative, software is provided in the \hysplit4\examples directory to convert output for display in GrADS (Grid Analysis and Display System).