10.6 Shapefile Overlays


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In the previous section we created shapefiles to display in ArcExplorer. However, the option to use shapefiles to replace the map background files when plotting trajectories or air concentration expands the application of these programs. Continuing on from the previous section, you should have the polygon air concentration shapefile concplot.shp in the /working directory. In this example we will overlay a trajectory with the concentration contours. If not, rerun the previous example.

  1. The first step is to go back to the trajectory example and recreate the mid-boundary layer trajectory. To save time, use the traj_fwrd_control.txt file to configure the simulation. However, to compare the results with the concentration patterns, only the first 11 hours of the calculation are required.

  2. After the calculation has completed, open the menu and change the map background file to shapefiles.txt. This should already be in the /working directory from the last example, but if missing it can be found in /tutorial/maps. Change the time label to hourly and reduce the zoom and the final graphic shows the first 11 h of the trajectory.

  3. The next step is to open shapefiles.txt in notepad and add a line at the end to open concplot.shp. Use the same line thickness and color scheme as the county boundaries line. Then delete the first two lines, representing roads and county boundaries, save and exit. Rerun the display program and now the graphic will show the trajectory over the concentration contours.

  4. An alternate approach is create shapefiles for the trajectory and add it to the concentration plot. For this application, reopen the trajectory display menu and select the GIS-lines radiobutton. Execute the display to create the generate format GIS_traj_* files in the /working directory.

  5. Now open the Trajectory / Utilities / GIS to Shapefile menu and select the generate format GIS_traj_*.txt file and selecting the lines and trajectory radiobuttons. Process the data to create trajplot.shp in the /working directory.

  6. Now edit the shapefiles.txt file again in notepad and replace concplot.shp with trajplot.shp and set the RGB colors to black (0.0) and then run the concentration display program using shapefiles.txt as the map background file to display the trajectory and concentration contours.

This type of overlay procedure is available through any of the plotting programs that support the shapefiles map backround option. In addition to trajectories and concentration, shapefiles can also be created from the meteorological data contouring program.