Instinct altimeter goes bananas

Yesterday I  made 15km bike ride in my neighbourhood... the maximum height difference is about 40m... I started at home at 33m, somehow went to over 1500m and arrived back home at 250m

I set to auto calibration based on GPS (I presume), stayed on the roads, calibrated 3 time during the trajectory... nothing works

- how do I calibrate and set the watch correctly?

- Is riding the bike or running a problem for the altimeter?

Thanks for a your help...

  • What was the barometer reading at start and finish? Did you calibrate the barometer to the correct pressure when you calibrated the elevation?  For example, let's say you calibrated your watch to 33m and the barometer is off saying it's 30.20 inHg when it's actually 29.09 inHg. Once you start, the barometer will correct itself to the correct pressure. If this happens fairly quickly, the watch will misinterpret this pressure change as a change in elevation. 

  • I presumed it would be a calibration issue. Question: how do I calibrate to get reliable result... knowing that I do not necessarily have the correct height or barometric pressure? I presumed it was calibration via GPS as the DEM does not seem to be available... but, when I did this "on the road" it seemed to give acceptable values at first, but minutes, still standing on the same spot of flat land, I found myself some 1500m higher according the altimeter... so, I'm doing something wrong.

  • One possibility is that the sensor opening is clogged with sweat or dirt. Also gusts of wind, or fast bike descents can create false pressure signals. Check out the other threads about altimeter on the Instinct forum - there are several of them, with some hints how to prevent this kind of behaviour.

  • I didnt realise you have to calibrate barometer and elevation. I have been calibrating the elevation but how do I find out the figure to calibrate the barometer? 

  • The manual says:

    Calibrating the Barometer

    Your device was already calibrated at the factory, and the device uses automatic calibration at your GPS starting point by default. You can manually calibrate the barometer if you know the correct elevation or the correct sea level pressure.

    1. Hold MENU.
    2. Select Settings > Sensors & Accessories > Barometer > Calibrate.
    3. Select an option:
      1. To enter the current elevation or sea level pressure, select Yes.
      2. To calibrate automatically from your GPS starting point, select Use GPS.

    But these options seem to no longer exist with SW 6.60.  There seems no way to set the barometer directly.

  • >But these options seem to no longer exist with SW 6.60.  There seems no way to set the barometer directly.

    You sure? I still have them.

  • Select Settings > Sensors & Accessories > Barometer > Calibrate.

    You can get to the calibration even quicker:

    Long-press ABC » press GPS » Calibrate

  • I did some tests. I performed a calibration as accurate as I could, with introduction of current altitude and barometric pressure and then observed the pressure and altitude over time both in a fixed location and during a bike ride over relatively flat terrain.

    As long as I did not move fast (cycle, wave arm...) the altitude remained within 10 m of the actual, varying only with barometric pressure (probably due to the inaccuracy of the initial pressure and altitude I used). The moment I start moving a little too energetic, ride my bike or even blow lightly near the sensor hole, the altitude is off... when I stop, it (slowly) resettles to a more correct value.

    Conclusion for me: the altitude measurement is not really useable when you perform an activity. The measurement principle or the placement and shape of the sensor/sensor housing do not seem suitable for the job in those conditions. Perhaps it is possible to alter the algorithm or to modify the sensor/sensor housing to get better results. Perhaps I will be able to enjoy an improvement on my "instinct", perhaps it will require a new model...

  • I know where the calibration settings are, just wondered where to get the barometric air pressure value for calibration from. I found a Barometer app and check that against local weather readings. 

  • Conclusion for me: the altitude measurement is not really useable when you perform an activity.

    That is a known issue, and I already wrote you should read the other threads about it, here on the Instinct forum. The problem is not only wind (and speed), but also sweat and dirt. There are some tips helping to improve the functionality, in the other threads. For example you can cover the opening with a tape (preferably little bit permeable), mesh, or a foam. You can protect it by a sleave or a sweat wrist band. You should frequently dry out sweat cummulating under the watch.