*UPDATE* Wind Speed on Wunderground **solved **

[bsparks]

I ran the debugging mode from SSH and what I get is at the end of this post.

Looking at this, it appears that the rounding errors in the wind speed are actually coming from meteohub, maybe in the km/h to mph conversion?

It's weird to always see .9s on the end of wind speeds and to never see 3 mph.



temp10: 294
hum: 66
dew10: 224
press10: 10030
sealevel10: 10057
wind10: 13
gust10: 4
winddir: 198
winddirstr: SSW
rain: 0
todayraintotal10: 2
todaymintemp10: 226
todaymaxtemp10: 311
todayminhum: 59
todaymaxhum: 94
todayminsealevel10: 10056
todaymaxsealevel10: 10096
todaymaxgust10: 67
monthmintemp10: 115
monthmaxtemp10: 328
monthminhum: 35
monthmaxhum: 98
monthminsealevel10: 10036
monthmaxsealevel10: 10215
monthmaxgust10: 89
yearmintemp10: 29
yearmaxtemp10: 328
yearminhum: 26
yearmaxhum: 100
yearminsealevel10: 10036
yearmaxsealevel10: 10281
yearmaxgust10: 116

WEATHER UNDERGROUND
normal: /usr/bin/wget -t 2 -q -O /dev/stdout \"http://weatherstation.wunderground.com/ ... 2008-05-10 22:38:40&winddir=198&windspeedmph=2.9&windgustmph=0.9&humidity=66&tempf=84.9&rainin=0.00&dailyrainin=0.01&baromin=29.71&dewptf=72.3&UV=0.8&solarradiation=148.0&indoorhumidity=0&softwaretype=meteohub\"
Reply: success

[admin]

Meteohub stores wind data in tenth of m/s.
Therefore wind10=13 means 1.3 m/s.

The following line generates the wind speed output for wu:

Code: Select all

p += sprintf (p, \"&windspeedmph=%.1f\", wind10 * 0.2237);

When I compute myself, I also get 2.9081 which correctly rounds to 2.9.

What weather station are you using? Having that, I can check the sensor
reading code that is responsible for wind10=13.

[bsparks]

It's a Davis Vantage Pro2. It just seems weird that my station would _never_ log a 1mph or 3mph wind on Wunderground. You can see that here:
http://www.wunderground.com/weatherstat ... =KLAALEXA5

Also,
http://www.wunderground.com/weatherstat ... =KMIROCKF4

displays the same behavior. That's cbhiii's station.

Thanks!

[bsparks]

Boris,
I know you've been busy getting 2.3b and 2.3c finished, but have you had a chance to look at the wind speed code for the Davis stations?

Thanks!

[admin]

Hi,
I drilled down a bit on this one. I think I have found the reason.
vantage reports in mph, Meteohub converts to metric (here tenth of m/s).
Storing data in tenth of m/s some rounding occurs. When Meteohub
reports wind speed to weather underground this rounding affects
orginally reported 1 mph to 0.9 mph. In general this is no brainer,
but when reporting a number with decimals as a wind speed to WU,
it looks like WU just cuts off the decimals, which leads to 0 mph.

As a result a windspeed of 1 mph, reported to WU as 0.9 mph is taken
by WU as 0 mph :-(
When the vantage reports 2 mph, this time rounding has not that an impact
and Meteohub reports 2.0 mph to WU, which results in 2 mph.

So we have a mapping of values:
0 -> 0
1 -> 0
2 -> 2
3 -> 2
4 -> 4
...

In the next update I will cahnge the WU code that way that Meteohub
reports a rounded mph without decimals to WU. That should solve the problem.

Sorry, tht it has taken that much time until I discovered the magic here ;-)

[bsparks]

Looks good so far! I appreciate you looking into this for us. I will keep an eye on it, but it looks like the problem is indeed solved.