The Data Collection PC is a standard pc clone running Microsoft
Windows. A custom application - Ice Station Zenith - written by the author
using Delphi, runs full time on the pc and performs many functions.
Ice Station Zenith communicates with the station
via RS-232, receiving real-time data measurements and sending various
commands as needed. The program takes advantage of Delphi's form
inheritance so that it can interface to different brands of weather
stations with minimal recoding. This is an important feature since Heath
no longer supports the weather station currently in use, which will
eventually need to be replaced.
All data values are periodically stored in an internal database for
archival and querying purposes.
In addition to the current weather data measurements obtained from the
station, the program also calculates three derived entities. Dew Point and
Heat Index are calculated based on the current temperature and the
relative humidity, and Wind Chill is calculated based on current
temperature and wind speed. For all displayed values, the user can select
from among all common measurement units from the Preferences menu.
As can be seen in the screen shot, several other types of historical
data are also displayed on the main screen, including the day's high and
low for temperature and humidity, 24 hr change for several of the
measurements, and all-time record measurements for some of the
measurements, among others. A planned feature of the program, though not
yet complete, is the ability to query the stored data for whatever
information the user might want. For instance, the user could request the
average high or low temperatures for a given month, or the average
rainfall in a given month.
Finally, the outdoor temperature, barometric pressure, and wind speed
measurements for each of the last 24 hours are shown in graph form. This
gives a quick visual indication of the values and rates of change of these
measurements over the last 24 hours. These graphs are implemented using
Delphi's support for custom components. The graphs are highly generic-
they can represent any kind of numerical data with any number of elements,
making them reusable in other applications which display historical data.
To produce a web page that can be displayed by a visitor's
browser, the program reads in a web page template
in XML form, parses the document, and substitutes the current weather data
for custom tags in the template. It then uses FTP to send the parsed
document to the web server. Since the template is in
XML form, it's appearance can easily be changed with any text editor or
html editor. No modifications to the Delphi program are required! The
template can also be extended (one of XML's primary features) with the
addition of new tags. This would require only minor modifications to the
Delphi program to support the new tags.
