Post by hvrooyen on Dec 31, 2018 22:16:40 GMT -8
Hi:
Weather rack on Raspberry Pi weather station running V3.02 code occasionally returns wind gusts that are *below* the average wind speed - see IEASTERN37 on WUnderground. Also, the gusts are (as opposed to occasionally incorrect low values) usually measured to be much *higher* than they are in reality (judging by the feel of the wind, as well as compared to METAR at FAEL - an airport about 30 km away).
Three comments/questions here, related but admittedly contradictory:
1. I cannot see from the code how gusts can be measured as lower than average wind speed, but I assume it may have something to do with reset_wind_gust being called at an inopportune time?
2. I may just be daft here, but in the following code:
weatherStation.setWindMode(SDL_MODE_SAMPLE, 5.0)
#weatherStation.setWindMode(SDL_MODE_DELAY, 5.0)
It seems the 5.0 is a sampling period? What is the maximum sampling time allowed? I can find no implementation of SDL_MODE_DELAY in SDL_Pi_Weather_80422.py. How do the different options affect program flow? Is a delay introduced in the main loop when sampling with SDL_MODE_DELAY ?
3. It seems to me (considering I do not fully understand the code - see above) as if the average wind speed sampling time is 5 seconds, while the gust speed is momentary (from one pulse to the next?). A quick search on Google seems to indicate that wind averaging should be over periods of a few minutes, with gust averaging occurring over at least a few seconds - see
www.wmo.int/pages/prog/www/tcp/Meetings/HC31/documents/Doc.3.part2.pdf
and
ijsetr.com/uploads/621345IJSETR1044-354.pdf
Weather rack on Raspberry Pi weather station running V3.02 code occasionally returns wind gusts that are *below* the average wind speed - see IEASTERN37 on WUnderground. Also, the gusts are (as opposed to occasionally incorrect low values) usually measured to be much *higher* than they are in reality (judging by the feel of the wind, as well as compared to METAR at FAEL - an airport about 30 km away).
Three comments/questions here, related but admittedly contradictory:
1. I cannot see from the code how gusts can be measured as lower than average wind speed, but I assume it may have something to do with reset_wind_gust being called at an inopportune time?
2. I may just be daft here, but in the following code:
weatherStation.setWindMode(SDL_MODE_SAMPLE, 5.0)
#weatherStation.setWindMode(SDL_MODE_DELAY, 5.0)
It seems the 5.0 is a sampling period? What is the maximum sampling time allowed? I can find no implementation of SDL_MODE_DELAY in SDL_Pi_Weather_80422.py. How do the different options affect program flow? Is a delay introduced in the main loop when sampling with SDL_MODE_DELAY ?
3. It seems to me (considering I do not fully understand the code - see above) as if the average wind speed sampling time is 5 seconds, while the gust speed is momentary (from one pulse to the next?). A quick search on Google seems to indicate that wind averaging should be over periods of a few minutes, with gust averaging occurring over at least a few seconds - see
www.wmo.int/pages/prog/www/tcp/Meetings/HC31/documents/Doc.3.part2.pdf
and
ijsetr.com/uploads/621345IJSETR1044-354.pdf