Altitude/elevation fallback to GPS

[Panagiotis Kritikakos]

@maszop Not sure about that. In the past were watches from Suunto with non-baro (Suunto 9) and there are still GPS devices in the market that use GPS for altitude/elevation. Surely much more accurate than a faulty baro sensor Also, considering how easily baro is affected on specific watches due to wind and rain, GPS would be more accurate. Right now, I’m relying on other platform’s mapping model data for getting my activity’s elevation but that’s post-activity which doesn’t help during the actual activity.

[maszop]

@Panagiotis-Kritikakos Outside of very strong winds, Suunto altimeters are doing great.
Other manufacturers are doing well also in strong wind, so it’s worth pushing Suunto to improve it.

Using GPS to correct altimeter errors is a road to nowhere.

[Panagiotis Kritikakos]

@maszop Agreed. The point here is not that baro is not doing good. I understand also specific conditions in relation to design etc. But as mentioned, I’m mostly talking about what could help a faulty baro sensor that delivers nothing. If I don’t send my 3.5year old watch for service (which would cost surely enough money that perhaps do not justify the fix) then I have zero altitude/elevation data. And by the way, FusedAlti is there. It is being used for fixing, why not for complete relying on faulty sensor?

[Brad_Olwin]

@maszop said in Altitude/elevation fallback to GPS:

@Panagiotis-Kritikakos Outside of very strong winds, Suunto altimeters are doing great.
Other manufacturers are doing well also in strong wind, so it’s worth pushing Suunto to improve it.

Using GPS to correct altimeter errors is a road to nowhere.

What @maszop said is spot on. GPS only is useless in my opinion as well. I have tested several watches Suunto 5 Peak and Suunto 5. Elevation gain/loss is not good.

[Panagiotis Kritikakos]

@Brad_Olwin I’ll repeat myself. Right now, I have no elevation because the sensor, or the software, do not actually work. That’s why I said “fallback”. What is more inaccurate than no data? Anyway. Close the thread if you wish.

[Brad_Olwin]

@Panagiotis-Kritikakos I think it requires different firmware as well. Not sure if this is present in watches with barometers

[thanasis]

@Panagiotis-Kritikakos there is a replacement watch on your desk

[Stefano M64]

from GPS the actual altitude can be derived with a certain known error, depending on the accuracy of the 3D fixing. Barometric altimeters give pretty accurate altitude readings, under the condition that no significant atmospheric pressure variations occur, otherwise they can be also wildly wrong, and there is no way to know if and how much the altitude is wrong. The longer the activity, the more probable that atmospheric pressure changes occur, especially on mountains.

[maszop]

@Stefano-M64 said in Altitude/elevation fallback to GPS:

Barometric altimeters give pretty accurate altitude readings, under the condition that no significant atmospheric pressure variations occur, otherwise they can be also wildly wrong, and there is no way to know if and how much the altitude is wrong. The longer the activity, the more probable that atmospheric pressure changes occur, especially on mountains.

For many years now, barometric altimeters have been doing very well even with large changes in atmospheric pressure.
In the case of Suunto, the only problem may be strong wind. Suunto copes very well with the rest of the factors, even during very long activities.

[Stefano M64]

@maszop said in Altitude/elevation fallback to GPS:

For many years now, barometric altimeters have been doing very well even with large changes in atmospheric pressure.

How? the altitude readings are indirect measurements based on the variation of the atmospheric pressure at different heights. A barometer simply cannot be “aware” if such variations are caused by changing in the elevation or by the weather conditions. Sometimes my SR shows that I’m lying some tens of meters below the sea level and I’m not a scuba diver!

[Mff73]

@Stefano-M64 said in Altitude/elevation fallback to GPS:

@maszop said in Altitude/elevation fallback to GPS:

For many years now, barometric altimeters have been doing very well even with large changes in atmospheric pressure.

How? the altitude readings are indirect measurements based on the variation of the atmospheric pressure at different heights. A barometer simply cannot be “aware” if such variations are caused by changing in the elevation or by the weather conditions. Sometimes my SR shows that I’m lying some tens of meters below the sea level and I’m not a scuba diver!

Suunto calls it : Fusedalti.
Baro altitude correction thanks to GPS measurement. Small variation are handled with baro, and potentially drift tendency or other calibration, with GPS (they are taking GPS “precision” to ensure that corrections are made when GPS altitude is significantly good.
Non speaking about wind, thus baro peaks, which are for sure another story.

[thanasis]

@Mff73 well do the following … during an activity try to submerge the watch into water while being stationary you may have a variation of several hundred meters . I did this while cross a 5m wide river and it showed as if I had 2000m ascent and descent . Had it worked properly it could have used other sensors as well and limit the ascent -descent indication to a less arbitrary number

[Stefano M64]

@Mff73 said in Altitude/elevation fallback to GPS:

Baro altitude correction thanks to GPS measurement. Small variation are handled with baro, and potentially drift tendency or other calibration, with GPS (they are taking GPS “precision” to ensure that corrections are made when GPS altitude is significantly good.

I was talking about “pure” barometric altimeters, of course FusedAlti should avoid wrong readings, but not always works as expected

[Brad_Olwin]

@thanasis said in Altitude/elevation fallback to GPS:

@Mff73 well do the following … during an activity try to submerge the watch into water while being stationary you may have a variation of several hundred meters . I did this while cross a 5m wide river and it showed as if I had 2000m ascent and descent . Had it worked properly it could have used other sensors as well and limit the ascent -descent indication to a less arbitrary number

The sensor is sensitive to changes in pressure and measuring very small changes. Water is essentially a sledgehammer for the sensor. The deeper you go the worse the issue. Water flowing across or into the sensor area will cause this. When you use snorkel mode or mermaiding the barometric measurements change and the pressure underwater is measured. It is difficult to have a single sensor do both.
I don’t know how the Ocean or Fenix 8 watches address this issue.

[maszop]

@Stefano-M64 It just works. At least in the case of Garmin and Suunto. These are more complex algorithms than the primitive calculation of pressure differences.

What you are writing about does occur in Hammerhead (Karoo) equipment, where there are simply raw pressure values ​​converted to altitude, and in this case it works very poorly.

[Stefano M64]

@maszop said in Altitude/elevation fallback to GPS:

For many years now, barometric altimeters have been doing very well

I was driven in error by your sentence, “barometric altimeters” rely only on atmospheric pressure changes. Suunto’s FusedAlti uses the GPS to correct drifts in the barometer not related to altitude changes, so it’s a mix between barometric and GPS altimeter (but not always works as expected). The statement I read in this forum several times, that the Barometric altimeter are better then GPS’s, is basically wrong.

[maszop]

@Stefano-M64 Altimeter data from GPS alone is usually useless. There’s no point arguing about it.
Even Strava automatically rejects it and replaces it with its own data.

[Panagiotis Kritikakos]

The point here is not if GPS is good or better than baro. I think all have their pros and cons and it’s good to combine them when needed as with FusedAlti. My point is that it would be handy/useful to have it as a full fallback when there’s problem with baro.

@thanasis hm… I’ll check it out when I get back

[Stefano M64]

@maszop said in Altitude/elevation fallback to GPS:

Altimeter data from GPS alone is usually useless. There’s no point arguing about it.

you’re right, the are no reasons to replay to you.