Alti -12m while at sea level

Ries22

Hi,

My suunto race 2, keeps saying I’m at -12m (and sometimes -22m) below sea level while I’m in front of the sea. I’ve tried to search the forum but haven’t found a solid answer to solve the Alti. Manual set, keeps being overwritten, cleaning the watch didn’t help . GPS sync doesn’t help.

Any ideas to tackle this issue would be welcome. The watch is on latest software.

surfboomerang

@Ries22 The altimeter works on air pressure. Wind or clothing that presses against the barometer sensor can have a huge impact on the altimeter

Squirrel

@Ries22 said:

Manual set, keeps being overwritten

Isn’t that normal with any pressure based altimeter?
You set a reference value but it will ultimately drift over time as the atmospheric pressure changes.
I would be more interested to know what value you get from automatic altitude adjustment.

sky-runner

Ambit 3 Peak has an option to auto calibrate altitude from GPS outside of activity. It took 5-10 minutes but was fairly accurate. Is that no longer available?

Update: I have just checked - this feature to auto-calibrate altitude from GPS is still available. On Ambit 3 Peak I had a button shortcut to go straight to auto-calibration so I used it often - before most trail runs. Unfortunately in modern watches an ability to use button shortcuts is very limited.

Ries22

@Squirrel ,

The automatic setting gives -4 to -6m but that gets overwritten as well.

What’s the usecase for this type Alti meters? (Maybe I’m using it wrong, I was trying to get the height changes of my running training in the mountains).

How to use the manual change, if it gets overwritten within couple of minutes?

Ries22

@sky-runner

It has indeed the automatic gos correction , which is slightly off -4 to -6m.

Normally I’m not using the Alti as my home country is pretty flat but I’m using it basically for the first time on holiday in the mountains.

johann.fuehrer

I also tried to explain that in the Garmin forums, but I think it was not understood there. The height ‘calculation’ on GPS devices is not that easy as it might look like. There come several factors together.
.) idealized model of earth for GPS - the earth is not a prefect globe or ellipsoid. So where is the 0 in height?
.) maps reference system (like i.e. WGS 84, which I assume all of you will have set in the system settings of the watch). I suggest to check out here: https://en.wikipedia.org/wiki/Spatial_reference_system
.) you can choose a position format in your watch, if you use a paper map as well, they need to match
.) Garmin devices also have DME (Digital Elevation Model) which they use to correct GPS height based on your position in addition with barometric measurement (works OK).

It’s not easy for a GPS watch to decide what’s your REAL zero elevation at the location you are …

I hope this helps a bit against the frustration not to see the exact height you actually are (but do you REALLY know, which map system does the map you use have?)

Btw: you might run into similar issues (in a very low range) on the position you are as well (paper map compared to GPS location).

MarkG

@Ries22 If you just want the height changes then it doesn’t really matter - the watch will still record the changes (and your overall climb and descent) regardless of how close to reference altitude it is. The accuracy is only important if you are navigating traditionally and need to know your exact altitude.

smedberg

@Ries22 This is roughly my experience too but with the Suunto race. I live at sea level and I would say the majority of my runs show a few(~5m) below sea level on flat sections right next to the sea.
As stated previously in this thread I think the relative variations(elevation gain) is mostly good quiality, just slightly ofset.

I do experience that for biking and walking the elevation data is more accurate. Showing ~1m when actually next to the sea. Probably due to less wind disturbance on the sensor. Possibly the vertical oscillation in running is also having a negative effect on the sensor?

Danny Labrana

Looks like a problem I reported a few months ago. In y cas, I ran at seal level and yet my Race 2 considered I statarted my run at +49 meters and despite the flat route, the max reported height was of 63 meters. Posting the permalink here in case the feedback I received can help: https://forum.suunto.com/post/192613