Technology behind the chart
(See related discussion in the installation
- Data-Collection Scripts
- Perl: Some of the data
behind the chart is gleaned (screen scraped) from web pages. Please
refer to the FAQ on data sources. This includes
the HMS web page and the two NOAA web pages. A Perl script runs
every 5 minutes and collects all the text from these pages and
then parses out wind, temperature, and pressure data. Perl has
useful features for manipulating text data. This data is inserted
into a MS Access database on the server. The charting application
then gets its data from the database.
- Python: The MN data added in
2006 uses a scheduled Python script to download and parse METAR data from an XML
- Database Connectivity
- MDAC (Microsoft Data Access Components): This
package of components, once installed, gives you the option to use ODBC
- ODBC (Open Database Connectivity): Database
connections provide the linkages for the Perl and Python scripts
and the ASP code to read and write to the MS Access database.
- Active X Data Objects (ADO): ADO
objects were used in both the Perl script and the ASP code. The
data objects support queries and manipulation of the data in the
- MS Access: The Perl script
populates a local MS Access database (mdb file) on the server. The database
stores the HMS data in a resolution of 15-minutes and the NOAA data
in a resolution of 1 hour. One of the charting options, delta-P,
makes use of SQL queries that serve to join the pressure records from
different sites and calculate their differential pressures.
- Charting Scripts
- ASP (Active Server Pages): This
is what makes the dynamic chart possible. It collects the form parameters
and runs queries on the local MS Access database. It then creates
a chart image (JPG file), using ASPChart. The ASP code then acts
to write the HTML code (for the web page), which includes a needed reference
to the image file.
- VBScript (Visual Basic Scripting Edition): The
ASP code is primarily written in VBScript which is a subset of VBA (Visual
Basic for Applications).
- ASP Chart: This is a freeware
charting component for ASP. It produces the chart image.
the code that supports the timer function.
- Microsoft Expression Web: Editor
for laying out static HTML pages.
- Notepad++ and VIM: Editors for the code.
- Operating System: It all runs on
MS Windows 7, 8 or 10.
- IIS: Internet Information
Server. This is Microsoft's web server and executes the server-sided
code of the charting page (ASP).
- MS Window's Scheduling Service: The
Perl and Python gleaner scripts are scheduled to run every five minutes
throughout the day.