News items for tag weathermapsite - Koos van den Hout

I noticed some funny stuff on the maps plotted at the weather map site. Non-fitting temperatures like 28°C in the south of the Netherlands where it is -4°C to -8°C according to the people who know. Or 5°C at site 'EHDV' which was plotted somewhere in the eastern part of the country, near Marknesse, but the reading for Marknesse was not the same.

The first error was caused by the recent upgrade at home: Ubuntu comes with Geo::METAR 1.14. I did not notice this right away because they did fix the error about only accepting metar data from the USA. So I put in my own Geo::METAR which fixes the parsing. The other error was that EHDV was in the wrong location in my data. Searching using google found that EHDV is the code for oil platform D15-FA-1 which is also hard to find, but somewhere deep in the data history of air traffic control the Netherlands is the right location out on the North Sea. Where it is indeed a lot warmer than in the east of the country, thanks to less cold wind from the east and more warm wather from the Gulf stream.

I noticed that the entry for De Bilt, Netherlands at the weather.gladstonefamily.net site had recent weather data. I asked Philip Gladstone where he gets that data and searched around a bit myself. The answer is that this is synop (surface synoptic observations) data. The synop data format is ofcourse very different from the METAR format. Time to find good data sources, write another parser and see what this can do for http://weather.idefix.net/. Probably time to split the whole script that generates the weathermaps in several parts, fetching, parsing and caching data, drawing the resulting data on the map.

After a 'complaint' that temperatures were mapped to almost the same shades of green I tried to find a better way to map temperatures to colours for the weather maps on http://weather.idefix.net. What I learned sofar: visualizing temperatures in an easy to understand way is quite hard. The human perception is that blue is cold and red is hot. The current mapping uses that to map temperature to Hue values and use the resulting HSV colour (after conversion to RGB). Adding a legend showing what temperature maps to what colour helps a bit, but with the Netherlands being not too big an area for weather and with usually not much differences in temperature I keep ending up with close shades of the same colour. Interesting problem, and I can't find any published work about this sofar. Lots of research in 3d weather visualization, but no temperature to colour mapping information.

A few updates to the weather maps recently: The maps are now generated each hour and there is a list of the recent weather maps.

Updates to the logic behind the weather maps at http://weather.idefix.net/ and updates to the stations list. Data is now fetched from multiple sources and with a lot of searching I found the locations of a number of stations such as EHFS (Vlissingen), EHSC (Lichteiland Goeree) and EHKV (oilplatform K14-FA-1C). Starting tomorrow morning the updates will be visible in the generated maps.

The weather keeps me interested and I have been working on processing weather data (ofcourse using Geo::METAR). Roger Burton West did a lot of work on visualizing weather data and I updated the result for Geo::METAR. Resulting maps now available on http://weather.idefix.net/. Stuff to add: caching, getting data from several sources (at least one metar for the Netherlands isn't available via the US national weather service) or using different sources.