[Xastir] Re: Wind Gusts

[Clay Jackson]

I started to compose this at 0930 this morning; just before our  
landline phone, DSL and internet all collapsed - as they say, "when  
all else fails,  Amateur Radio".

In any case, the problem with using single measurements is that some  
stations (like the Davis) give you just that when you poll them - an  
"instant" reading.  So, if you poll every minute and there's a gust  
in between polls, you lose.  Now, the Davis DOES keep two "high  
speed" measurements, one that's "highest speed since last poll" and  
the other that's "highest speed since last reset".   Meteo grabs the  
"highest speed since last poll" every time around its loop, which is  
about a minute, and puts that into a "gust" value.   On the speed  
side, the wind speed is the speed at the instant the reading (poll)  
is taken, so you can't take that for a high speed calc at all.

So, what I did yesterday afternoon was hack db2APRS to select the  
highest gust in the last 10 minutes from the database, and to average  
the wind speed and direction over the last 2 minutes , and that's  
what it's reporting to Xastir.

Interesting dilemma....

Clay
==========

On Dec 14, 2006, at 9:42 PM, Curt Mills wrote:

> On Thu, 14 Dec 2006, Clay Jackson wrote:
>
>> Well, I think I found the issue:
>>
>> In wx.c, at line 427, in cycle_weather, wx_speed, not wx_gust was  
>> getting
>> passed to compute_gust.
>>
>> Here's the diff:
>>
>> 427c427
>> <             computed_gust = compute_gust((float)atof(weather- 
>> >wx_gust),
>> ---
>>
>>>             computed_gust = compute_gust((float)atof(weather- 
>>> >wx_speed),
>>>
>>
>> if you look at my data going to findu, it's now reporting much  
>> more reasonable
>> gust (32MPH so far this evening, the power's out and the storm  
>> "center" is
>> still several hours away).
>
> I believe the idea is that we're computing the gust ourselves from
> the wx_speed value due to averaging time mismatches between the
> weather stations and the spec.  I think the wx_speed value there is
> intentional.
>
> -- 
> Curt, WE7U.				archer at eskimo dot com
> http://www.eskimo.com/~archer
>   Lotto:  A tax on people who are bad at math. - unknown
> Windows:  Microsoft's tax on computer illiterates. - WE7U.
> The world DOES revolve around me:  I picked the coordinate system!"
>