Advancing Water Resources Research and Management

• Creating and Accessing Data
• Displaying Data
• Zooming
• Viewing Time Series Plots
  
• Display Details  
   

I. Creating and Accessing Data for Display

    Data Selection

Precipitation totals to be displayed are written into files by choosing the Java display option in the access routine GETHPD.  Filenames thus created are automatically added to a listing file ("contents.txt") whose contents are displayed in a box on the upper left of the Java display.  Filenames consist of the beginning date of the summation period of the data (in the format YYYYMMDD), then the extension HPD followed by either LST (local standard time) or UTC (Universal time) and the extension HR, DY, or MO (for time intervals of hours, days, or months, respectively).  If alternative filenames are desired, their names can be added to contents.txt.
 

Although data files created after the the display routine is started will not be automatically shown on the display menu, editing their names directly into contents.txt and clicking on the Refresh list option will bring them onto the menu. When the desired filename appears on the menu, clicking on it and then clicking the Load Data button will load and then display data in that file. Depending on the speed of your browser, loading may take several minutes for large files.  The progress of the loading procedures can be monitored by observing the number of data loaded shown in the yellow title box.  Loading can be terminated at any time by clicking the Stop Loading button in the loading information window.  Selecting a new datafile and loading it will automatically supercede the previous data while leaving all options set.  A description of the data files themselves can be found here, or in the documentation accompanying this software disk.

    Map Display

Precipitation totals (inches) are plotted at HPD station locations as colored squares coded according to the color bar beneath the display. Small gray squares indicate operating stations reporting zero rainfall during the period. Open squares indicate at least one unavailable hourly report. It is possible to display stations reporting only specified amounts of precipitation by clicking on an individual increment (color) on the color bar or by dragging (clicking and holding the mouse button while moving) the cursor over a range of increments. All other colors will be Xed out on the color bar and those stations will not appear on the map. Clicking on any non-Xed-out color on the color bar will display all observations. Increments along the color bar can vary from plot to plot depending on the duration of the requested summation (changes occur at one day and one week).
 

Positioning the cursor over a station displays that station's precipitation amount, geographic description, and identification number. Latitude and longitude of the cursor are continuously displayed above the map as the cursor is moved across the map.

Clicking on the Values button will display precipitation amount at all stations. Clicking on the Rivers or Counties button will display rivers and county boundaries. Clicking on the Grids button displays latitude and longitude grid lines at one-degree intervals. To change the default grid intervals, shift-click (hold down the shift key while clicking the mouse) on the Grids button and set the desired interval in the box which appears.
 

This display applet can only display HPD stations in the continental 48 states.

III. Changing the display scale (Zooming)
 
    Zooming

It is possible to zoom the display to see greater detail or to separate crowded observations.  This is done by locating the cursor at a corner of the desired zoomed area and dragging the cursor (holding the button down while moving the mouse) until the desired zoom box is produced. (The zoom box maintains the aspect ratio of the overall box, so may not follow the mouse cursor quite the way you initially expect.)

The Un-zoom button returns the display to the immediately previous setting.  If, after a series of zooms, it is desired to return directly to a full national display, click on the Reset button.  The size and location of the zoom box can also be changed in another way.  In the overview box which appears when the Overview button is pressed, the present location of the display is outlined. This option is useful if after several zooms the location of the box is not clear.  Dragging when the cursor is within the zoom box will move the box while retaining its current shape.  The overview window can be closed in the usual way, or by clicking again on the Overview button.
 
 

 Clicking the mouse when the cursor is located over an individual station will open a new window containing a bar-graph time series of reports from that station during the data period loaded. The time increment will be hourly, daily, or monthly, determined by selection when the data is accessed by the routine GETHPD. Included with the time series are station information (name, description, numerical ID, latitude and longitude), total precipitation, and information about data irregularities. Missing data are indicated by a yellow line beneath the plot, deleted data by a green line, and accumulating data (that is, multi-hour amounts that are not shown until the end of the accumulation period) by a black line. Moving the cursor across the time series plot will display the individual amounts and status indicators ( D, M, and A for deleted, missing, and accumulating); clicking on an individual time increment, or dragging across several increments, will bring up a new window showing the acumulated precipitation and information about data gaps (if any) during the selected sub-interval. Time series windows can be closed in the usual way, or all can be closed simultaneously by clicking on the Close TS button above the plot.
 

The map consists of 325 state boundary segments, 537 river segments (at 15 km resolution), and 3860 county boundary segments (at 20 km resolution). These segments, originally in latitude/longitude coordinates, were remapped to Lambert's conformal conic projection, tangent to the globe at 20 degrees north latitude, and centered at a longitude of 95 degrees west. Points on the segments were coded as 2-byte signed integers in the range 0 to 32000, where the point (0,0) is the upper left hand corner of the map. We call this coordinate system 'java-conus-1'

 

The Overview button on the applet reveals or hides a small window showing a national map. The region shown in the main applet window is indicated as a rectangle in the overview window. You may move the rectangle in the overview window by dragging with the mouse. To move, place the mouse inside the rectangle (the cursor will change to a 4-pointed arrow) and drag. The rectangle's new size and location will be reflected in the main window shortly after you release the mouse button (1-2 seconds on my 166 MHz machine). Tip: if you lose track of the overview window, try clicking the Overview button twice. Another tip: you can always use the Reset button of the applet to bring the map back to its initial configuration (while still showing the currently loaded data).

 

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