Basin Customization - Localization Lab

Objective: Prepare shapefiles for FFMP localization on AWIPS.

This process creates the final basin and bin shapefiles to be used with FFMP. FFMP requires a polygon shapefile to define the basins and a point shapefile that represents the center point of each 1 degree by 1 km DHR data point. The basin shapefile must contain a field named [Pfaf_id] that contains a unique Pfafstetter ID for each basin. The bin shapefile must contain a point for each 1 degree by 1 km radar bin in the DHR product and contain a field named [Pfaf_id] that identifies the basin the bin maps to.

The basin shapefile must be processed so there are no basins without bins and all basins meet a minimum area threshold. Removing small basins is required to minimize FFMP CPU usage as much as possible and to ensure all basins can be resolved on the D2D display. The bins shapefile must be processed to include the [Pfaf_id] value corresponding to the basin the bin is within.

There are two aspects of the radar coverage that also need to be considered:
  1. The maximum range from the radar reasonable precipitation estimates can be derived. This maximum range is highly site specific and is based on radar site elevation, terrain blockage and precipitation climatology. The maximum range is estimated from experience using the radar's precipitation products and is not a predefined setting on the WSR-88D. Basins beyond the maximum range should be deleted to eliminate computations in areas where good precipitation estimates can not be generated. This can be done automatically in the "Merge By Bin" function by first selecting the bins where good precipitation estimates can be computed.
  2. Only bins that are not blocked should be mapped to the basins. Since FFMP calculates area averaged accumulation, known bin locations that have invalid data due to ground clutter or beam blockage should not be used in the calculations to avoid biasing the basin accumulations.

Step 1 - Merge Basins Without bins

Procedure:

  1. Start ArcView and open project basins/cust/localization.apr.
  2. Open View1.
  3. Make the Kxxx_bins.shp theme active by clicking on its legend.
  4. Click the "Query" button.
    1. Build the following query string: ([Range_km] < 200)
    2. Click the "New Set" button.
    3. Close the Query window.
  5. While holding the Shift key down, click on the legend for the Kxxx_ref_basins.shp theme to make both the Kxxx_bins.shp and the Kxxx_ref_basins.shp themes active.
  6. From the Bsn-Tools menu, select "Merge By Bin".
    1. Name the new file "wsbin.shp".
    2. Answer "Yes" to prompts to recompute area.
    3. During the final merging step, the view may be automatically zoomed to selected features (via "Merge w/Next Downstream"). You will be prompted on whether to merge all the indicated basins together. Answer yes to these prompts.
  7. Click on the "Clear Selection" button to clear the selection on the Kxxx_bins.shp theme.
  8. Check to make sure all basins have a bin:
    1. Make the wsbin.shp theme the active theme by clicking on its legend.
    2. Click the "Query" button.
      1. Build the following query string: ([has_bin] = 0)
      2. Click the "New Set" button.
      3. Close the Query window.
    3. If any basins were selected, you would have to examine each selected basin and merge it with an upstream or downstream basin that has a bin using the "Merge Basins" function on the Bsn-Tools menu. Then redo the "Merge Basins Without Bins" step using the new merged theme.

Step 2 - Merge Small Basins

Procedure:

  1. Make the wsbin.shp theme the active theme by clicking on its legend.
  2. From the Bsn-Tools menu, select "Merge By Area".
    1. Enter 1 for the minimum area threshold in square miles.
    2. Name the new file "wsarea.shp".
  3. Make the wsarea.shp theme the active theme by clicking on its legend.
  4. Check for basins that could not be merged (these will generally be outlet basins):
    1. Click the "Query" button.
    2. Build the following query string: ([Area_sq_mi] < 1)
    3. Click on the "New Set" button.
    4. Close the Query window.
  5. There should not be any selected basins in this example. If there were any selected basins with area less than the threshold, you would have to examine each one and determine if any further action is needed. Most of the selected basins will be outlet basins ([Parent_id] = 0) and can probably be deleted. Otherwise, merge these basins by selecting an upstream or downstream basin to merge with and use the "Merge Basins" function.
  6. At this point, all basins should have bins and be greater than the minimum area threshold.
  7. A temporary theme named "Merged1" was added to the view during the "Merge By Bin" processing. This theme can be deleted from the view and from disk using the Source Manager.

Step 3 - Map Bins to Basins

  1. Make both the Kxxx_bins.shp theme and the wsarea.shp theme active:
    1. Make the Kxxx_bins.shp the active theme by clicking on its legend.
    2. While holding the Shift Key down, click on the legend for the wsarea.shp theme to make both the bins and the basin themes active.
  2. Click on the "Open Theme Table" button to open the attribute tables for both themes.
  3. In both tables, select the [Shape] field.
  4. With both tables open, make the Attributes of Kxxx_bins.shp table the active window and click on the "Join" button. This will perform a spatial join and add the basin attributes to the Kxxx_bins.shp theme attribute table.
  5. From the Table menu, select "Start Editing".
  6. Make the [Pfaf_id] field the active field.
    1. Click the "Calculate" button.
    2. Double click on the [Pfaf_orig] field so [Pfaf_orig] appears in the lower left part of the Calculate window.
    3. Click the "OK" button. This will set the [Pfaf_id] field to the values in the [Pfaf_orig] field.
    4. From the Table menu, select "Remove All Joins".
  7. Return to the View and make the Kxxx_bins.shp theme the active theme.
  8. Select bins that should be excluded from FFMP calculations (known ground clutter areas and blockage areas). For blockage areas which are generally wedges, use queries to select specific azimuth and range sectors and use "Add to Set" in the Query Builder window:
    1. Click the "Query" button.
    2. Build the following query string: (( [Range_km] > 10) and ([Azimuth_dg] > 270) and ([Azimuth_dg] < 272 ))
    3. Click on the "New Set" button.
    4. Build a second query string: (( [Range_km] > 20) and ([Azimuth_dg] > 344) and ([Azimuth_dg] < 347 ))
    5. Click on the "Add to Set" button.
    6. Two sectors of "bad" bins should now be selected. Close the Query window.
  9. Click on the "Open Theme Table" button to open the attribute table for the Kxxx_bins.shp theme.
  10. Make the [Pfaf_id] field the active field.
  11. Click the "Calculate" button.
    1. Enter 2 double quotes "" to reset the [Pfaf_id] to a null string.
    2. Click the "OK" button.
  12. From the Table menu, select "Stop Editing" and save the edits.

Step 4 - Set "Pfaf_id" field in basin shapefile

Procedure:

  1. Make the wsarea.shp basin theme the active theme by clicking on its legend.
  2. Click on the "Open Theme Table" button to open the attribute table for the wsarea.shp theme.
  3. From the Table menu, select "Properties".
  4. For the field [Pfaf_orig], enter "Pfaf_id" in the Alias column and click on the OK button.
  5. Return to the view.
  6. Ensure the wsarea.shp basin theme is the only active active theme.
  7. Click on the "Clear Selection" button to clear any selection on the theme.
  8. From the Theme menu, select "Convert to Shapefile".
    1. Enter "kxxx_aggr_basins.shp" for the new name.
  9. Remove the "Pfaf_id" alias from the basin theme attribute table:
    1. Make the wsarea.shp basin theme the active theme by clicking on its legend.
    2. Click on the "Open Theme Table" button to open the attribute table for the wsarea.shp theme.
    3. From the Table menu, select "Properties".
    4. Remove the "Pfaf_id" for the field [Pfaf_orig].
  10. Clean up unneeded tables and themes.
This completes the steps to create the final versions of the FFMP shapefiles. Move the new shapefiles to AWIPS for localization. The shapefiles must be named "kxxx_bins" and "kxxx_aggr_basins" replacing "kxxx" with the appropriate radar ID. The actual filenames that must be moved to AWIPS are: Once on AWIPS, you must gzip the following files before running localization: