Freediving depth meter + surf time

Hello,

I would like to make simple freediving app

1) Depth meter
Ive played with that on Suunto Ambit 2
this should be formula which worked with Suunt - (pressure - 1013.25) / (10.26*9.81)

2) Surf time
Time count which start when you reach surface (based on pressure) and should be reseted to 0 once you swim to -1m

I dont have much time to work on it but should start this weekend and will see

TTower over 10 years ago

any plans to extend this into the epix?

Semi666 over 10 years ago

x

So I finally had chance to take Garmin Fenix 3 to some depths. Ive used ConnectIQ depth / max app to check depth and was also using Aeris F11 freediving computer.

Good news Garmin Fenix 3 could withstand pressure at 41m without problems (constant weight freediving). Unfortunately with current apps max depth which could be measured is 16,2m (or 16,7m not sure but it was bellow 17) so its fine for measuring depths during snorkeling but not for freediving or diving.

Ill be glad to join force in developing freediving app :)

Former Member over 9 years ago

I have also been toying with making a freedive app, but have encountered the same issues with the Garmin pressure readings. Unfortunately GetSensorInfo does not reveal raw pressure readings. As you correctly figured it is a Garmin-calculated number. If I find a workaround I will share it back here.

Looking at the API it seems like the pressure info reported is adjusting for the change in altitude from the altimeter (reports pressure at sea level), thus the pressure responds back to the "sea-level pressure" because the altimeter is reading the height change. Now, if we could set a value for the altimeter and effectively "turn the altimeter off" then we should be able to stop the loop that is readjusting the "pressure at sea-level" to report the actual pressure reading. I'm not a programmer, yet if someone could try this it would be awesome!

Former Member over 9 years ago

Silly question, but in the testing of these apps was the autocalibration of the elevation turned off or more ideally set to 0? Anyone want to check this? maybe it will fix the pressure returning to the out of water pressure, enabling the use of the barometer and not just the altimeter.

Former Member over 9 years ago

6335

If you run the calculations through this basic program it seems to suggest that the biggest difference that you can measure is the atmospheric equivalent elevation change of around 9000 m (0 m - 1013.25 to -9000 m - 2677.77, negative for altitude to have higher pressure) the difference between these two being 16.645 m according to the program calculations. Thus it seems that this is mostly software limited either in the API for activity.altitude itself or in the basic programming of the fenix (kernel?).

Just my two cents. Any thoughts from Garmin?