Wind Question & how do I correct it?

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scotty
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Wind Question & how do I correct it?

Post by scotty »

I have owned and used iBike/Newton for the past 6 years. For 5 & !/2 years it has always seemed to be accurate with wind stats. In the last 1/2 year, it has never given me a ride where the wind, is greater than the speed. A common experience before, those were the days where there was no wind, then major headwinds when turning around. Now it seems like the wind speed for the whole ride is consistently 3.5 to 5 miles slower than the ride. Which means I have a nice tailwind for the whole ride. In fact there are times I will check the wind on the ride and it will show a tailwind minus numbers (for example a -2) for wind speed, while I am watching leaves, etc. blowing towards me while Newton indicates a tailwind. And we all know what it is like to ride into a headwind.

I have followed the wind calibration details, just like I always did in the past to no avail. Still consist minus numbers

How do I correct this & bring back the wind speed accuracy that I have experienced prior to 6 mos. ago?
Velocomp
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Re: Wind Question & how do I correct it?

Post by Velocomp »

Please post a ride file that shows your problem.
John Hamann
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Re: Wind Question & how do I correct it?

Post by Pete »

I find that the wind sometimes "corrects" after doing an 'analyse route'.
Particularly I regularly notice that a tailwind will be corrected to a 'drafting' scenario.
Just thought I'd mention it as it might be more of an altitude/inclination thing than wind itself.
scotty
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Re: Wind Question & how do I correct it?

Post by scotty »

John,

Thank you for looking at the file. Sure would like to know why all my rides now average around a 3 mph tailwind.
Attachments
iBike_07_30_2014_1049_45_Miles.ibr
This was an out & back ride, wind direction & speed seemed fairly constant for the whole ride.
(600.67 KiB) Downloaded 307 times
Velocomp
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Re: Wind Question & how do I correct it?

Post by Velocomp »

Load the attached profile into your Newton and see if this corrects your issue.
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Scotty_Profile.ibp
(581 Bytes) Downloaded 318 times
John Hamann
scotty
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Re: Wind Question & how do I correct it?

Post by scotty »

Thanks John, I will test it out on my next couple of rides and let you know.
texmurphy
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Re: Wind Question & how do I correct it?

Post by texmurphy »

Pete wrote:I find that the wind sometimes "corrects" after doing an 'analyse route'.
Particularly I regularly notice that a tailwind will be corrected to a 'drafting' scenario.
Just thought I'd mention it as it might be more of an altitude/inclination thing than wind itself.
On a group ride today I had strong outbound headwind (NW wind and rode NW for 20 miles) with a matching return tailwind.
When I do Analyze Route to correct elevation for Start=End, it indicated about 5% Drafting.

I did take turns drafting on the outbound headwind but I rode with no drafting for the entire tailwind return. When I look at the Drafting indication on the Cadence chart, Isaac got it 100% reversed. It shows no drafting during the headwind outbound when I did draft. But I am shown drafting during the tailwind return when I did not draft.
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racerfern
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Re: Wind Question & how do I correct it?

Post by racerfern »

texmurphy wrote: On a group ride today I had strong outbound headwind (NW wind and rode NW for 20 miles) with a matching return tailwind.
When I do Analyze Route to correct elevation for Start=End, it indicated about 5% Drafting.

I did take turns drafting on the outbound headwind but I rode with no drafting for the entire tailwind return. When I look at the Drafting indication on the Cadence chart, Isaac got it 100% reversed. It shows no drafting during the headwind outbound when I did draft. But I am shown drafting during the tailwind return when I did not draft.
I personally don't like the Analyze Route options. They're awesome if something goes wrong like the unit comes loose, rain, wind port blocked. But assuming the ride was completed without a problem then I simply check the radio button for enter known elevation and enter the starting and ending elevation which is usually the same. Nothing else is checked since Newton obviously knew when I was in a tailwind and when in a headwind. Be careful because checking Ride ended where it began will assume an average wind speed of zero and that isn't necessarily the case. Cars, drafting, changes in weather all cause deviations that hardly ever yield wind=0 for the length of the ride.
Fernando
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Russ
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Re: Wind Question & how do I correct it?

Post by Russ »

tesmurphy and racefern,

I do normally use the route correction as it is rare that the barometric pressure stays same over my ride and if the wind wasn't steady (normally the case) check the 'wind changed' box. This way it will only correct the elevation and if I find that the wind dropped of rose on average during my ride which is usually closed loop of some kind I may go back manually into the wind correction and give it a smidgen of correction so that I feel better about it :lol:

Russ
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racerfern
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Re: Wind Question & how do I correct it?

Post by racerfern »

Russ wrote:tesmurphy and racefern,

...so that I feel better about it :lol:

Russ
There are a million ways to make yourself feel better so you may want to look at other options. :roll:
Fernando
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Russ
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Re: Wind Question & how do I correct it?

Post by Russ »

raceferen,

Thanks for the advice, I really need it this morning :)

But actually and seriously, with a look at the local personnel weather stations around and the tables of wind measurements, along with studying the wind display is Isaac, sometimes I think an educated guess is likely to improve accuracy. That said in defense of the technique, it certainly isn't very scientific and I understand that a scientist would not be able to defend the technique in his paper.
However in computers (my field) we have heuristic techniques and tweeks applied to make thing work better. :lol:

Russ
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Re: Wind Question & how do I correct it?

Post by Russ »

Jose and Fernando,

Here are two examples of my tweeked rides. Yesterday's ride first, without applying about half of the wind correction that Isaac calculated, nearly all of the wind shown was on the high side. The wind died to zero nearing the end of the ride. During that period there was a clear negative but I was drafting a semi that had just turned in front of me :-) So if you revert to original ride file, you will see the unequal wind. The wind during the rest of the ride, according to a personnel weather station very near to the starting point, was somewhat variable in direction but predominantly WNW, more or less with one data point from the South near start of ride. The 'official' NWS airport nearby only posts hourly readings.
iBike_12_13_2014_1427_46_km_N Loop.ibr
Ride with half of Isaac calculated correction for wind applied.
(665.24 KiB) Downloaded 297 times
Next is a ride from prior weekend where I rode a long section SW and during that time the wind was fairly steady from the NE with gusts. This was a windy day. Two personal weather stations, one a bit SW of the end of the SW ride section and another NE of the ride but further away, both show a lot of NE winds with gusts. The more NE one, perhaps 10 miles away show the time period of the higher NE winds >< and hour prior to the other more SE station, accounting for the aprox 10 MPH steadier winds arrival time.
My ride had several 'low power' high tailwind display sections where, like Josej, I was pushing steady more like the rest of my ride.
I applied a 'blocked wind sensor' correction specifying zero wind speed to those section and the power became more inline with what I would have expected based on my memory of the ride, same day. Also a higher power than average downhill section emerged but I specifically remember trying to push for higher speed there, just for fun. Again, if you revert to original data, you will see the change. Look for a few clearly zero wind section mid on the SW leg before reverting.
iBike_12_07_2014_1353_43_km_River_Studly Loop.ibr
SW leg corrected for high tailwind displayed that was a high crosswind.
(660 KiB) Downloaded 288 times
Fernando, please explain where I erred for my education, if you are convinced that I did err (thanks in advance).

Regards,
Russ
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racerfern
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Re: Wind Question & how do I correct it?

Post by racerfern »

Russ, before I dig into these files, are these the originals as downloaded from Newton?
Fernando
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Russ
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Re: Wind Question & how do I correct it?

Post by Russ »

Fernando,

These are 'corrected' as discussed above. I expect they should be as original when you select analyze - return to original download.
I do not have auto correction selected.

This is why I suggest taking note of the points of correction before returning to original to see the difference made. But then I guess you can reload the file to see that.

Here are a couple of links to the two weather stations I referenced for the older high NE wind ride.
This first one is just a bit South of the end of my SW run:
http://www.wunderground.com/personal-we ... KVAMECHA16
This second one is, I guess 10 miles North of the SW leg of my ride....
http://www.wunderground.com/personal-we ... =KVAAYLET2

I do have the gps data merged in so you can see the map somewhat or get exact locations, if you prefer.

Thanks again,
Russ
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racerfern
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Re: Wind Question & how do I correct it?

Post by racerfern »

@Russ:

Sorry for the delay, life got in the way; again.

I looked at both files, returning to the original download and I have to honestly say your efforts are not worth the time IMO. The 46km is virtually unchanged.

For the 43km ride, there is more of a difference than in the 46km. However, I think the changes you made reduce the wind more than it should have. The section from 14-24km shows a tremendous tailwind which of course I can't verify.

It seems your profile is spot on so IIWY I would simply correct for starting and ending elevation with nothing else checked. At least you will have consistent recording which I think is far more important than changing recorded data to match personal weather stations that may or may not truly reflect the ambient conditions in a very small area which may or may not have anything to do with the rest of your ride. How's that for a lot of may or may nots... it becomes easier to ruin data rather than improve it.

My 2¢
Fernando
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Russ
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Re: Wind Question & how do I correct it?

Post by Russ »

Fernando,

I really appreciate your 2cents worth as being quite a bit more in value! And no problem with delay, especially understandable with the Christmas and new year holidays (happy New Year!).

I agree on the 46km ride, not worth the effort, but there, I think it did improve accuracy because my wind zero was off a tad which I think explains some of the level of wind correction called for in that case.

On the 43km ride, average power came up about 30 watts with the correction I made and I had taken mental note during that portion you mention (14-24), which is on the nearly straight SE leg, that there was a clear cross wind, not a tail wind at all.

So for whatever reason the iBike recorded it as an extreme tail wind, Newton was wrong during those times. I was especially conscious of the issue due to having reviewed Josej's file and read his complaint recently prior. This is why I went to the trouble of checking the two weather stations and in general they agreed with NWS forcast and each other, so I evaluate that in this case as probable cause level of reliability.

So at times there is some issue with Newton with cross winds. Typically it can be ignored but in my and Josej case seems it was worth applying a blocked wind sensor correction due to the relatively long exposure to those conditions.

Thanks and great to have your confirmation on my profile too!

Russ
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racerfern
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Re: Wind Question & how do I correct it?

Post by racerfern »

I still think you're overestimating the wind effects in a cross wind situation. Granted, crosswinds can be a challenge but I think mostly because our body tends to disturb the wind flow as it gets to Newton. However, I still think the difference is minimal and not something you should make corrections for. I also notice that even even though you corrected for the "middle" section, the first and last third have notably higher wattages. Perhaps you should split the file into threes, work on the middle section and then unite them.

I spent the last few days looking for an article I "think" I remember reading about the sail effect of cross-winds. Depending on the angle, crosswinds can actually be beneficial if coming at you from a significant yaw angle. Unfortunately I haven't had the time to drill into the subject.

http://sheldonbrown.com/brandt/wind.html

http://www.roadbikerider.com/riding-ski ... iding-wind

http://www.aeroplanner.com/calculators/avcalcdrift.cfm
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Russ
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Re: Wind Question & how do I correct it?

Post by Russ »

Fernando,

You said:
"Perhaps you should split the file into threes, work on the middle section and then unite them."
Interesting idea! I may play with that some, after I read your provided links.

Really appreciate your time,
Thanks,
Russ
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