METEOSAT image

In this picture I've plotted data from METAR reports as synoptical symbols that, amongst other things, shows pressure, temperature, dewpoint plus wind speed and direction. Note that the wind direction is plotted relative to the picture's x/y plane and not its lon/lat plane. Cloud coverage and some weather types are also indicated. Areas around stations with precipitation are colored green.

Isopleths for pressure, temperature and relative humidity can also be plotted onto the image (part of the whole image) - here only isobars are plotted. The method for this is based on delaunay triangulation implemented in C by Steven Fortune.

In the picture above the background was taken from the Dundee Satellite Receiving Station, Dundee University, UK, and the data are taken from LFV.

The program above is implemented using Perl and Tk. The program exists in three versions, the one above, interactive, another that, using GD for Perl (cf. libgd) only generates a picture, suitable for web pages, and finally a version that generates a background image for the computers desktop.

All versions use a cache for the images, thus saving internet bandwith. The desktop version, however, gets its METAR data from a local database that every half hour fetches METAR-data.

During developement I also tested saving images. While doing this the satellite images were updated every 30 minutes, enabling the making of the odd animation using ImageMagick.