Help for FSL's HPD Java Display
and Accessing Data
Time Series Plots
and Accessing Data for Display
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.
Loading the Data
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.
data and station information
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
Text Display / Buttons
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
the display scale (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.
Series at Individual Stations
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.
V. Display Details
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'
Page prepared by Ed Tollerud, email@example.com
modified: Mon Sep 21 11:32:07 1998
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).