Instinct 2x Solar Altimeter problem

I agree on initally setting the watch but it should atleast hold the inital altitude for a few hours after setting especially when staying in the same area. I understand that atmospheric pressure affects the watch which is normal. The watch is only 2 months old and the port is not clogged. Unfortunately it doesnt hold the fixed setting. My comments are not meant to be hostile at all, just explaining the facts. Thank you for the help, i appreciate it very much.

Gonzo said:

I think there is some mis information here.  Let me comment hopefully accurately....

• "MSL IS barometric pressure" - MSL is not barometric pressure.  MSL = mean sea level.  Has nothing to do with barometric pressure.  Its a "average height" of the sea level and from that barometric measurements are taken.

You lost me with your first sentence - which is misinformation and inaccurate.

Our watches display barometric pressure at MSL (Mean Sea Level).

Barometric pressure at any Elevation other than MSL is called Absolute Pressure - our watches do not display this value.

The advantage of using pressure at MSL, other than being consistent with all other official weather reporting facilities, is that as the Elevation of the watch changes, pressure displayed as an MSL pressure remains constant.  Any variation in displayed pressure can then be monitored more accurately to predict changes in the weather.

The disadvantage of using Absolute Pressure is that as Elevation changes, the displayed pressure changes - making weather tracking impossible.

HTH

I was quoting from a previous post that mentioned "MSL IS barometric pressure"  but that isn't correct.

I don't believe you are correct about Absolute Pressure - Absolute Pressure is a value read from a sealed vacuum.  Not sure how you use your watch but I am using it outside, at ground, in a unpressured aircraft and hikes, I don't think that would be considered a sealed vacuum.    The user manual doesn't mention Absolute Pressure  but does mention barometric pressure 5 times.  So I'm pretty sure the 2X is using barometric pressure.    Between the users elevation change and pressure changes due to atmospheric changes the watch will ALWAYS have to be calibrated.    Hence from the manual "The barometer displays environmental pressure data based on the fixed elevation where the altimeter was most recently calibrated". 

Perhaps it could help on the user's activity to set the Altimeter sensor mode most effectively which could help reduce (not eliminate) the need for calibration throughout the day:

Auto Cal.: Allows the altimeter to self-calibrate each time you use satellite systems.
Sensor Mode: Sets the mode for the sensor. The Auto option uses both the altimeter and barometer according to your movement. You can use the Altimeter Only option when your activity involves changes in altitude, or the Barometer Only option when your activity does not involve changes in altitude.

trux said:

The vertical accuracy accuracy of GPS is ~+/-150m,

I should have been clear auto cal if you not using one of the other 2 options.  Otherwise when you cal the altimeter you could use the GPS to acquire DEM data to set altitude.  Never knew about the accuracy of GPS is ~+/-150m... I always thought it more along the lines of +/- 25M.  Not too bad.

I think the watch is defective. I set the manual altitude 2 times within the hour and havent moved and it still says its 23 feet higher than i really am. I also selected altimeter only as the sensor. The trend of elevation still increases. The watch is not good for measuring accurate altitudes and really unreliable unless the software is fixed. What good is the feature if one has to constantly calibrate it ? Reading all these posts are not helping and contain much opinion and specualtion. 

Could be defective.  Return / exchange hopefully you will have better luck.

I have 2x tactical

I set altimeter and barometer mode to auto 

For two weeks accuracy was very good, almost excellent , altimeter very stable during weather changes, barometer readings very close (+/- 0.3 mb) to national weather station readings

But last night, when i used the widget from controls to see the altimeter or barometer, accuracy is bad. Altimeter readings change fast during weather changes, barometer not very accurate (2 mb out)

I didn't change altimeter and barometer modes, still on auto mode. It seems that altimeter and barometer mode changes automatically on the widget, on control panel 

Does anyone else experience same strange thing?

honestly, got watch replaced due to similar behaviour. year later and it happens again. funnily it happens winter time, so I suspect temperature changes impact barometer a lot.

Going outside to run in cold, once settled, altimeter is generally showing ok. But just outside activity, well, it will travel by meters with hardly any move. 

I am afraid this sort of sensor is just, simply put, rubbish, after some time something starts going wrong with it.Or it's software changing mode for no reason. But either way we should not be seeing sudden altitude changes nor pressure changes if we sit tight, so must be more than that :(