Absolutely! That's what the CdACrr app + weathermeter does. For some reason I thought el gato was referring to classic VE without airspeed, since that's what most people are familiar with.

I only know of one person who is getting good field testing data with the Aeropod, and that's using it as an airspeed sensor only (mounted outboard of the basebar handle) and VE analysis is done in a spreadsheet

That doesn't entirely surprise me.

I hope Garmin will come out with proper support for aero fields in the .FIT protocol and ANT+ specification. All we really need is an ANT+ or Bluetooth Smart enabled wind meter...
This should be a < $50 device. You can build one today for $60 (retail cost) in parts.

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What's your CdA?

Attached below is the fit file straight from my Garmin 820. John took a look and apparently I wasn't on the latest firmware for that ride, so it may not have the data that a file created with the new firmware did.

I'll update the Aeropod firmware, do another test session, and post the file here.

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Amateur recreational hobbyist cyclist
https://www.strava.com/athletes/337152
https://vimeo.com/user11846099

Yep, aero data is missing from that file. Will be interesting to see after you update the firmware. Thanks!

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What's your CdA?

Edit: Table in post was scrambled in the upload. Photo of table in post below this one.

I’ve become something of a CdA addict (albeit not a very educated one) as I age and find that reducing my CdA is the only way I’ll get faster on my TT bike. I’ve recently started running comparisons across different approaches to see if any one of them appears to be more consistent than the others. El Gato asked for some comparative data so here’s some info from a training ride yesterday.
Ride location: open 380m velodrome track with 18 degree embankments. Coated asphalt surface. Smooth (but slippery as hell when wet). While open it is surrounded by trees and a solid fence about 4 feet tall so it is reasonably protected from wind. Enough to roughly halve Wunderground wind speed at track level based on data from an anemometer. Wind gusts though can still be a problem.

Weather (averaged over measurements from start and end of ride): temp 75; humidity 83; dew point 69; wind SW8-11mph (3-5 at track level); air pressure 29.163; rho 1.1474

Ride parameters: 4 CdA measurement intervals, 2 during warm-up and 2 training

• During warm-up: 1x6 minutes at endurance pace, 1x2.5 at near race pace
• Training: 2x12.5minutes at near race pace

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Primary CdA objective: see if I’m losing my aero position as I tire


CdA tools: Aeropod, Golden Cheetah (with and without airspeed data from Aeropod), MyCdA, Fast Aero Lab

CdA results (with assumed CRR of .0031 – data for Conti TT tires with latex tubes from BRR):

Interval
Int Length (minutes)
Aeropod
GC (with airspeed data)
GC (no airspeed data)
MyCdA
Fast Aero Lab
1
6.0
2120
2177
2271
2260
2040
2
2.5
2200
2177
No data
2160
2019
3
12.5
2250
2083
2212*
2320
2178
4
12.5
2190
2307
2333
2260
2121

Some notes:

• The airspeed data went into the GC "headwind" column
• I’ve asked Fast Aero Lab what their CRR assumptions are for the surface choices they offer since their numbers are always lower. I haven’t heard back
• *Obviously not the best conditions for VE-type testing though other than interval 3 the VE curves were very smooth. I was a bit fidgety on the bike in interval 3 a couple of times.
• I tried loading airspeed data from a csv file into MyCdA but without success -- since I'm assuming it's approach is very similar to GC I wanted to see if, with airspeed data, the CdAs would align more closely.
  

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A question for anyone: is GC with airspeed lower solely as a result of the inclusion of some form of wind yaw data?

Hey Matabele,

I develop MyCdA and would like to help out.

1) airspeed - can you send me your .CSV file so I can try and see why it won't import.
2) as far as how airspeed is used in calculation, in the virtual elevation equation - it's assumed that v_air is equal to v. When air speed (v_air) is available it's plugged into the CdA part of the equation replacing ground speed (v). It's pretty much how Golden Cheetah does it having looked at their source code as well.
3) can you send me the aeropod .FIT file - assuming it contains all the air speed measurements and stuff. This way I can add support for Aeropod files in MyCdA without needing .CSV

I've gone further and played with weather data from online services such as DarkSky and OpenWeather. DarkSky can give you minute by minute historical data which is pretty nice. Having this data and combined with GPS coordinates of the activity I can calculate heading and combined with wind direction and speed reported by the weather station I do some math stuff to calculate air speed and yaw. In some situations I've seen it work nicely - ran my own Ironman AZ file through the test - where wind direction and speed changed throughout the ride.
This assumes of course that you're not drafting, the weather data is accurate and from a location close to where you are and you're not being sheltered from the wind by terrain etc... Anyway, it's fun as an experiment - more in the best bike split territory than real VE testing :) This works in the current iteration - if file has GPS data just check the "Wind Model" checkbox it will automatically calculate air density adjusted for elevation, airspeed and all that stuff.

Edit: one more thing, there's a setting in your MyCdA profile for drivetrain loss adjustment. Depending on what power meter you use that could also explain some differences in in the calculations.
Also crr might be a little higher than roller test data even if you're on a velodrome. There are some methods to determine crr using the VE protocol. For example, starting slow and increasing speed few loops so that in the end there's only a unique combination of crr and CdA that will level the VE graph. (http://nyvelocity.com/...ess/the-shen-method/)

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What's your CdA?

Hey Trailerhouse,

Aeropod records as a .ibr file not a .fit file. It works with their software -- Isaac.I can if you like send you the complete .csv file for the ride if that helps but I don't believe I can convert it to a .fit file.

In the meantime, attached (hopefully) is the cleaned up .csv file I used for your site with columns for speed, airspeed, elevation, lap, power and time. I managed to load it into your site but it records every second of the ride as a lap which seems to be slowing it down a lot and not letting me get to do any CdA analysis. It also, when I flip back and forth between screens, somehow it switches from imperial to metric measures with numbers that don't appear to be accurate.

I have none of those issues with your site when I load a .fit file. Not being a techy, I suspect it may be something I'm doing.

I'm using a Powertap hub and have the drivetrain loss set at 1% (same as for Aerolab).

Here goes!

No, yaw isn't used.

I suspect your airspeed is high. Wind (airspeed-speed) is above 0 on average.

I see, the lap number needs to be repeated for each record. If you don't care about lap markers just remove that column altogether.

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What's your CdA?

I updated your file with lap markers. Should import fine now.

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What's your CdA?