interp 1.0.C

This is a project that returns interpolated temperature and humidity
values for a specific latitude and longitude within the US. It works by
finding a few weather stations that are nearby the desired input
latitude and longitude, creating distance-weighted averages between the
nearest station and the other stations that account for how far away the
point of inquiry is, then averaging all of the results together.

This data is interpolated, and as weather can be pretty local, the
further one gets from the nearest station, the more likely that the
values developed here may differ significantly from the actual fact.

Still, this enables one to make an inquiry, and within the limits of
what measurements are taken by the National Weather Service, it'll give
you a reasonably likely idea of conditions at points other than the
weather stations themselves, which is to say, the other 99.99999999% of
the USA. :)

To use this, there are three phases; the first is to go get a text file
which lists all the weather stations. I found the file at...

    http://weather.noaa.gov/data/nsd_bbsss.txt

...and put that in the local directory named NOAA.txt.

Then run interp.py, which will in turn create a file called "us_nws.txt"
which is a more useful list, being shorter (US sites only) and also
containing decimal-ized latitude and longitude values.

Once you have this file, you can run "demo.py" which will do the work of
taking the latitude and longitude in question (from demo.conf) and get
you the interpolated data against the nearest stations. To learn how it
works, see the Python (.py) files; I've tried to comment sufficiently so
the process is understandable.

Every once in a while, you'd want to refresh the files, as it is
possible that there will be new weather stations added, or some stations
may be shut down.

The XML data only changes about once an hour, according to notes in the
XML itself. Consequently, you should not attempt to fetch an
interpolation more than once an hour -- it's just a waste of bandwidth.
Be a good client, and only use what you need to.

This project was built and tested under Python 2.5.1, running under OS X
10.5.8. You can reasonably expect it to work in any modern linux
environment as well. It does depend upon various Unix/linux
characteristics, such as the availability of a /tmp directory (though
only when diagnostics are on), so it probably won't work under Windows.

Ben
AKA "fyngyrz"
http://fyngyrz.com/
July 2nd, 2010

Versions:
=================================================================
1.0.C	==	July 3rd, 2010
		--	More comments
		--	Output station list drops HI, AK, GU, PR (see demo.conf)
		--	Output station list fixes description case
		--	Output diag file path is in .conf file for OS compatibility
		--	Output graph now includes lat/long lines, better aspect control
		--	Output graph now includes station and interpolated results

1.0.B	==	July 2nd, 2010
		--	More diagnostics
		--	More comments
		--	readme file is versioned
		--	demo.py will generate graph of result if PIL is installed

1.0.A	==	July 2nd, 2010
		--	Original release version