4 ms·

I have one of Wahoo's cadence sensors, which I use with Strava on my phone, and have liked it. I was considering getting one of their heart rate monitors as wel

I have one of Wahoo's cadence sensors, which I use with Strava on my phone, and have liked it. I was considering getting one of their heart rate monitors as well. But seeing this casual misuse of GPL and Apache2-licensed software doesn't give me a warm and fuzzy feeling. As for GPS weirdness mentioned in the article, I'm wondering if there are some shenanigans going on in Android, or if I ran into some GPS jamming or some sort of selective availability? I took a ride along the Illinois side of Mississippi River north of the Quad Cities, and while I was near the Quad Cities nuke plant, my phone's GPS altitude readings were ridiculous - the altitude profile for my ride showed altitudes over 2,000 ft, when there are no such places in Illinois that high, save at the top of some skyscrapers in Chicago. This was consistent on both the outbound and return trips, with the anomaly occurring just south of Albany. Northward, the altitude readings were what they should be (in the ~600-700 ft range).

alexlrobertson 8y ago
Altitude is a tricky thing with these kinds of devices. They’re usually based on pressure readings from a sensor inside the device but that reading can be affected greatly by a number of factors. See https://groups.google.com/forum/m/#!topic/wahoo-elemnt-users/L7skAUrsVwk https://groups.google.com/forum/m/#!topic/wahoo-elemnt-users...
- ebikelaw 8y ago
  With all the people riding around with these sensors now, shouldn't it be possible to synthesize a very accurate basemap elevation from the reported barometric and GPS readings?
  - 07d046 8y ago
    Strava does this
    - alexlrobertson 8y ago
      Got a source? Strava segments in my area often have very wrong altitude data. Chicago is extremely flat yet there are segments that report gradients of over 10%, sometimes as much as 27%. I believe they are thrown off by buildings and the frequent elevated train tracks. https://www.strava.com/segments/1504604 https://www.strava.com/segments/1504604
      - 07d046 8y ago
        https://support.strava.com/hc/en-us/articles/115000024864-Announcing-Strava-s-Elevation-Basemap https://support.strava.com/hc/en-us/articles/115000024864-An... I'm guessing segments just use the elevation data of the activity that they were created from, hence why they can be wildly wrong.

alexlrobertson 8y ago

Altitude is a tricky thing with these kinds of devices. They’re usually based on pressure readings from a sensor inside the device but that reading can be affected greatly by a number of factors. See https://groups.google.com/forum/m/#!topic/wahoo-elemnt-users/L7skAUrsVwk https://groups.google.com/forum/m/#!topic/wahoo-elemnt-users...

ebikelaw 8y ago
With all the people riding around with these sensors now, shouldn't it be possible to synthesize a very accurate basemap elevation from the reported barometric and GPS readings?
- 07d046 8y ago
  Strava does this
  - alexlrobertson 8y ago
    Got a source? Strava segments in my area often have very wrong altitude data. Chicago is extremely flat yet there are segments that report gradients of over 10%, sometimes as much as 27%. I believe they are thrown off by buildings and the frequent elevated train tracks. https://www.strava.com/segments/1504604 https://www.strava.com/segments/1504604
    - 07d046 8y ago
      https://support.strava.com/hc/en-us/articles/115000024864-Announcing-Strava-s-Elevation-Basemap https://support.strava.com/hc/en-us/articles/115000024864-An... I'm guessing segments just use the elevation data of the activity that they were created from, hence why they can be wildly wrong.