Depth Data Field for Garmin devices

Garmin Connect IQ data field to show dive depth underwater for snorkeling, diving, and other water activities.

Warning

Be sure to check the water resistance of your unit before diving!

Installation

• Configure build environment
• Press Ctrl + Shift + P (Command + Shift + P on Mac)
• Choose Monkey C: Build for Device
• Upload prg file to your Garmin device GARMIN/Apps folder

How it works

I use pressure-to-depth calculation. This calculation uses simple hydrostatic pressure equations. The pressure, P of a fluid at depth depends only on the density, p, the acceleration of gravity, g, and the depth or height of the fluid column, h:

$$P = pgh$$

So, to get depth, we need to solve for h:

$$h = \frac{P}{pg}$$

To get actual depth, we need to use the current pressure, P(surface), so we can then calculate the depth, h:

$$h = \frac{P_{current} - P_{surface}}{pg}$$

I use the following values for these parameters:

P(surface) = 100.93 kPa, which is 1 atm at water level average,
p(fresh) = 997.0474 kg/m3,
p(salt) = 1023.6 kg/m3,
g = 9.80665 m/s2.

$$h = \frac{P_{current} - 100.93 * 10^3}{1023.6 * 9.80665} = \frac{P_{current} - 100930}{10038.08694}$$

There is no way to choose between salt/fresh water, so feel free to use FRESH_WATER_DENSITY instead of SALT_WATER_DENSITY constant.

References

Water density:

• Freshwater: 1 m = 9.78 kPa, 100 m = 977.77 kPa
• Salt water: 1 m = 10.04 kPa, 100 m = 1003.81 kPa

Limitations

I found no way to get the current pressure value more often than 1 minute. So I use the last pressure reading. If you have any information on how to get pressure more frequently, please let me know.