[wxqc] findu.com barometric pressure display issue

[Steve Dimse]

On Aug 1, 2006, at 7:40 AM, Thomas Hybiske wrote:

> Has anyone checked their wx page recently on findu.com?  I hope I  
> can explain this correctly because I don't know much about the system:
>
> The problem pertains to the display of the barometric pressure.   
> Looking at the displayed graph, it would appear there are gross  
> swings in pressure. In my case, my station shows a 5 millibar  
> change in a matter of hours; something that did not happen in the  
> dog days of summer here in New England.  I first suspected a device  
> problem at my station, but my Weatherlink display showed a nearly  
> smooth pressure line as expected.  Then I looked at other stations  
> and observed gross swings in pressure at their stations as well.   
> So I then went back and looked at my "quality control graph" for my  
> station and I think I've discovered the problem.  It appears that  
> the graph line has been "magnified" and layed down onto an  
> incorrect graph range.  In other words the graph line represents  
> minute changes in pressure, but is being tracked on a grid for a  
> much wider range of pressure.  Maybe a tenth of a millibar is being  
> traced as one millibar. I noticed this began sometime late last  
> week.  Can someone confirm this for me?  Here's my station address  
> for reference:  http://www.findu.com/cgi-bin/wxpage.cgi? 
> call=K3gm&last=120
>
As Philip mentioned, I added autoscaling, which is why the changes  
look far greater than they did before. However, I think the code is  
correct. Despite your protestations that 5 mb changes do not happen  
in a matter of hours, look at the data for your station:

http://www.findu.com/cgi-bin/wx.cgi?call=K3gm&last=120

from this I see that on 7/28 at 131332 you reported a pressure of  
1013.3 and at 210334 you reported 1007.7. This represents a drop of  
5.6 mb over 7 hours and 50 minutes. I believe this is accurately  
reflected in the graph.

Steve K4HG