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How exactly does altitude calibration work these days?

F0RMER MEMBER
over 2 years ago
Jeff_ODSWENG said:
If auto calibration is set to 'ON', we will calibrate to DEM at start.  We then continue to calibrate during the activity using GPS+DEM.

#1

Jeff_ODSWENG, and what about the general rules about altitude calibration AT START? (I mean those below, which are officially shared by Garmin)

Is this detailed description about the prioirity order used “AT START” calibration still valid?

See ”At Start - The goal of At Start calibration is to provide a consistent relative starting elevation for users that do multiple activities at specific locations. It will not calibrate again during the activity. When the timer is started the watch will try to determine the best elevation source to calibrate to, based on the following priority:

  • Click here to view priority list
    1. Manual calibration immediately prior to starting the activity
    2. Prior manual calibration point at the same location
    3. Recent manual calibration, if the quality of the calibration is determined to be good enough
    4. Map data (DEM), if available
    5. Prior Connected DEM point at the same location:
      • Connected DEM refers to elevation data from the Garmin Connect app on a paired smartphone
    6. Connected DEM, if currently connected to a phone
    7. Prior GPS point at the same location
    8. GPS, if a good fix has been acquired:
      • After acquiring a GPS fix the timer ring will turn yellow. At that point, it can take up to 30 seconds for the GPS elevation to settle. If vertical speed settles to less than .1 m/s the GPS elevation data will be considered good enough use for altimeter calibration.
      • Before starting the timer, the elevation data field on the watch will preview the calibrated elevation”

So far I relied on item 2, earlier same location calibrations, not just with 6X, but with 5+, 3HR, and also with 910XT.

Will items 1, 2 and 3 still work after 19.20?

#2

A side-question: does the number of (saved) locations used for altitude calibrations limited?

Or may I make manual altitude calibrations having GPS fix at unlimited locations without loosing the saved data (location+altitude) of the oldest calibrations?

NB: I moved this post of mine from another thread, because it was not replied there and I could not see any chance that  it would be under “sw 20.30” thread

  • 0 over 2 years ago

    Would indeed be nice to know. It seems to be difficult to get an answer from Garmin on the forum. Have you tried contacting support directly? They are usually very responsive. 

  • 0 over 2 years ago in reply to #Matthias#

    Sure, I have, but got no answer at all.

    Before the announcement of Fenix 7 they had been really responsive, but since then I got no response at all.

    Eg. appr. 2 weeks ago I reported a bug, and within 24 hours it was discussed between me and the support coleague and it was forwarded to Engineers.

    And last Friday I reported another bug, with exactly the same structure in my email, and I got zero reaction since then. Maybe outdoor support is flooded with F7 questions.

    Back to the subject, Garmin Chris was the only one who at least appreciated my inquiry to an extent that he reacted in a thread I hijacked a bit:-) , see: forums.garmin.com/.../1363568

    EDIT: and it seems that there is nobody in the already fairly active Fenix 7 forum who can confirm it, see https://forums.garmin.com/outdoor-recreation/outdoor-recreation/f/fenix-7-series/283395/wrong-altitude-calibration-before-start-an-activity/1362671#1362671

    I am almost sure that the altitude calíbration logics  of these newest outdoor wearables are fully the same as they are in the newest sw of Fenix 6, namely 20.30.

  • 0 over 2 years ago

    During many years the altitude calibration was one of Garmin’s most sacred secrets.

    Only since I am working as a researcher in the field of artificial cloud intelligence and with therefore unrestricted access to latest military grade blockchain technology, I was able to decompile the device firmware and to reconstruct the applicable computations using my institutes quantum assembler.

    Therefore, I finally can share the relevant formula with you:

    altitude = <duration of your last saved activity> * (your body weight in ng) / <number of updates the f6 will receive after the f7 release>

    * in case of a div0 cpu exception, a random number is assumed.

  • 0 over 2 years ago in reply to Beutelfuchs

    Ha-ha. I cant laugh on it, to be honest.

    I am not asking about any speciel secrets, I simply ask about whether the official priority list shared by Garmin support is still valid or not, see it here support.garmin.com/.../

  • 0 over 2 years ago in reply to F0RMER MEMBER

    Hey! Garmin seems to have modified the description in the last 24 hours. 

    So implicitly they confirmed that even in the new auto cal structure the first 3 options will work if it will be set to ON, and NOT NIGHTLY.

    So whining, whinging and nagging work as Young Sheldon used to say to his sister. :-)

  • 0 over 2 years ago

    DEM during activity can be a very bad idea in steep terrain. Some meters position error can result in several hundred meters of different altitude. I hope the algorithm is more intelligent now. I had to turn auto calibration off in steep mountain terrain, because it often caused crazy errors (more than 200 meters) despite correct GPS altitude.

  • 0 over 2 years ago in reply to 7535066

    Sure, the earlier option (only) ‘At start’ was the best option in this case.

    It is one of the reasons why I am still sticking to 19.20.

  • 0 over 2 years ago

    An official answer, or updated support article, is what we need but to give my 5 cents...

    What changed in the latest betas and newly released software is that the configuration option for auto calibration at start of activity is removed. We now only have two options for auto calibration: On or Nightly.

    The old option At Start is replaced with a prompt at start of any activity if the auto calibration setting is set to Nightly. In that prompt there are 4 options: Start activity with current calibration, Manually set an altitude, Use DEM or Use GPS.

    From what I understand the old priority list is gone, you decide every time. Also 2 and 3 from the prio list are gone. 

    What I don't understand is if Use DEM or Use GPS still do 4-5-6 and 7-8 or if they only do 4 and 8. I guess the later.
    Also the behaviour of 8 has changed slightly since it happens after the user selection as a separate step and not as part of acquiring GPS fix in the beginning of the activity.

  • 0 over 2 years ago in reply to TobiasLj

    Thanks for describing the prompt part of the story. It misses from the support article.

    But at least Garmin updated it, until yesterday it has been written so as to be the same as Fenix 5 or Fenix 5 plus, which was correct only until the sw version 20.30.

    I feel there is some clarity that if you accept the ON option, which is the old Continuous (including At Start), you wil STILL (!!!) get the items of 2 and 3.

    If you dont, and you would like to keep as much as you can from the At Start option you should use the prompt feature, as you described it.

    And it may happen that although it is not explicitly said, but implicitly the items  2 and 3 of the priority list are used in case of DEM and/or GPS options of the Prompt.