I have been playing with virtual elevation method for several years now (many thanks to Robert for this and all other guys who provided advices here on ST) and as recent threads pointed out, field testing ask us a lot of time. In order to reduce the time to collect data and analyse it, I recently wrote an Android app to monitor CdA and Crr on an ANT+ enabled phone and it needs an ANT+ powermeter (and an additional ANT+ speed sensor for crank PM). The main features are:
-Compute CdA on laps if mean velocity is high enough (given a Crr estimation)
-Compute Crr on laps if mean velocity is low enough (given a Cda estimation)
-Air density is calculated automatically with weather station data and the app try to use device sensor as much as possible (pressure, temperature if any)
-Data is recorded in 2 different CSV files which is possible to get for post analysis and comparison (for example via Aerolab in GoldenCheetah)
Edit: The app is today a part of an aero system as a anemometer may be connected: see https://forum.slowtwitch.com/...ost=6926334#p6926334 Edit (2021/12): Ant+ protocol is not necessary anymore for phone or sensors. BLE sensors are supported so any Android phone will run the app
I am testing now an other mode (segment mode) where CdA is computed on the fly with a limited precision (2 digits only) during a ride. Every 1.5 km (@35 kmh), a number is printed on the screen of the device. Of course it is a virtual CdA number cause it depends of wind and drafting, but it is very interesting to see the influence of drafting for example in a group ride…
Thanks, if you get a try with the app (it has been tested with PowerTap and Power2max for the moment and several ANT+ Sony or Samsung phones) and I am interested by any new feature request.
Thanks guys. If you have all the requirements (ANT+ phone & powermeter), you will see it works well. Field testing is not easier (wind and cars are still the enemy), but it is very cool to see immediatly the numbers instead of going back home after the sessions, switch on the computer, download the data, run your spreadsheet or Aerolab, find weather data on Internet, and compute at least. And there is a lot of new features currently waiting to improve the process…
Yes velodrome. If you have a look at the line “Device/ANT+ sensors”, you will see the roll angle of the device. Not used yet in the model (basically the virtual elevation method). But for a velodrome, it could be refined by implementing also the centripetal force thanks to the roll angle given by the phone sensors.
I loaded the app and checked the roll angle here in office on some known agles and that works well, but I am not sure where it is getting its weather data as it says it is 2.9C when it is much closer to 20C today
edit: oops, I see it says paris france, while rest of numbers could have applied to where I am
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I would really like to try this but I have an iPhone (on AT&T). I know nothing about Android phones. Does anybody know if I can buy a cheap unlocked android phone on eBay and make this work??? I see some cheap ones like Samsung Galaxy S3 III SCH-I535 -16GB- VERIZON UNLOCKED - Android Smartphone
Would this work? Do I have to have internet service? Since it is unlocked, can I stick my AT&T simm card in it?
I loaded the app and checked the roll angle here in office on some known agles and that works well, but I am not sure where it is getting its weather data as it says it is 2.9C when it is much closer to 20C today
edit: oops, I see it says paris france, while rest of numbers could have applied to where I am
You can change the location in the settings (as other infos like weight, tire circumference, CdA/Crr estimations,…). Default location Paris is in reference to the (first ?) ride shared by Robert several years ago showing the interest of VE method
Congratulations. Looking good. I’ll have to see if I can get an android phone with Ant+.
Thanks SkippyKitten, I follow your blog with interest and learnt a lot of things. An app receiving the wind information (by bluetooth?) from your Arduino card and merging with the ANT+ signal (speed, power) from the powermeter will be of main interest.
The S4 is one of the cheaper phones that is. Plenty for less than $100 on ebay that look serviceable. I may upgrade my 6 year old phone for this…
Yes, Samsung S4 contains 3 sensors (temperature, pressure, humidity) and thus air density is perfectly described with this phone. But, with no sensors and weather meteo data it is fine also.
I would really like to try this but I have an iPhone (on AT&T). I know nothing about Android phones. Does anybody know if I can buy a cheap unlocked android phone on eBay and make this work??? I see some cheap ones like Samsung Galaxy S3 III SCH-I535 -16GB- VERIZON UNLOCKED - Android Smartphone
Would this work? Do I have to have internet service? Since it is unlocked, can I stick my AT&T simm card in it?
Another cheaper option is the Sony Ericsson Xperia Active (2012). Small screen but robust, it has ANT+ support and includes a barometer which is useful for the automatic segment mode of the CdaCrr app. You will need to upgrade to Android 4.0 Ice Scream Sandwich, though.
Network is not mandatory for the app, it is useful to get weather data automatically and to upload the CSV files (results) by mail for instance to your laptop. But, you can specify manually weather data in the app settings and cable connect the phone to your PC to get the files directly after. Oh, and the voice record feature (to remember for instance the reason why a lap should be discarded, eg: a car drafted you) will not be available (Speech Recognizer needs network).
Thanks for the link, I did not know about this. I have an extra ANT+ stick I’ve been hoarding onto (have 3, use 2) and this seems like the perfect opportunity to use it. I’m going to find that cable to buy and then find some time to get this up and running. Definitely excited to try this out. Thanks!
