Hello everyone,
I'm hoping to find a way to obtain accumulated rainfall since midnight from APRSWXNET / CWOP stations. I've tried the following data sources, but all of them have problems:
OpenWeatherMap.org: this site hits systems that features data that's obviously originated from APRSWXNET. The problem is that many records/readings are excluded or missing. IOW, when I compare OWM readings with data from MADIS, it's not uncommon to find that only a fraction of the readings are shown in OWM.
MADIS: I've pulled several days worth of APRSWXNET data from this system, but the data are only available in "precip in the last hour" and "precip in the last 24 hours". It's difficult to extract *accumulated* rainfall from data reported in the format because the 1 or 24 hour window is always moving. I'm sure I could write an algorithm to calculate the total, but the readings aren't reported in regular intervals. For example, one station may have reported 1 hour precip readings from 1:05, 1:28, 1:35, 1:42, 1:58, 2:15. I can't accurately caluclate the total amount of rain that's fallen in the hour before 2:15 since the only readings near the past hour are more than 10 minutes off. This would be tricky but doable if they always reported on the same minute of the hour (e.g., 1:15, 2:15, 3:15, etc). This type of calculation would be doable, even with irregular reporting times, if it reported Rain Since Midnight (it'd be a simple sum and subtraction). Most of the APRSWXNET packets that are ingested by MADIS do in fact report rain since midnight in the token following the capital "P". But MADIS doesn't store this variable.
WeatherUnderground: many of their "personal weather stations" are APRSWXNET stations. The terms of use on their website saids that you cannot republish data. They have an API, but you can only hit one station per request and I'd quickly hit the 500 request/day limit if I pulled data from multiple station every 15 minutes.
HADS: I'm currently pulling rain data from their system - with permission. The probably is that they only transmit data hourly even though the station records data every 15 minutes. I'd like to have better temporal resolution than one hour and be closer to 'near real time'. And these stations are fairly geographicly sparce. There are quite a number of APRSWXNET stations located in key locations where HADS stations are absent.
There are a few well established and well know websites that have APRSWXNET summaries, but they explictly state that they don't want people pulling/scraping data from their websites on a frequent basis. That's understandable and I intend to fully respect that.
So is there a website that may have the data I'm seeking in a machine readable format? I have considered trying to connect to the APRS-IS stream and parse the packets, but I haven' been able to find any code that makes doesn't seem very complex. And I'm not sure how much bandwith that would consume and if my web host would appreciate that much traffic. Any suggestions?
