Negative Depth? - Fenix 5X

Every second day I am walking at about 5m below sea level. The altitude on this watch is another of the many bugged and never fixed aspects. So from this experience pretty sure it should give you negative depth readings as I went for a ride at -28m about 2 weeks ago. I am damn talented....

I noticed yesterday when heading to pick up the kids from school that my altimeter was showing -11meters.. I normally have it set to Baramoter if I'm home as my elevation doesn't change much through the day. I had left it on Auto following a bike ride and we had a storm coming in which I guess might have confused it. Wish you could set it to auto update altitude by GPS every hour or so..

Pitz and Kilt, the OP is asking about the watch's ability to record water depths.

Your replies are about an entirely different issue: Altitudes (in air) below sea level.

To Pitz, I further recommend that you read some of the many threads on altitude measurements. If you think that the watch is malfunctioning because it shows a negative altitude, you simply don't understand how a barometric altimeter works.

C1rclez, there was once an CIQ data field (or app?) for diving that someone had written but I believe it was pulled by Garmin as the watch is not considered a dive watch and is not supposed to be used as one. Possible the app/data field is available "off-line" - not sure. You could probably do up your own with one of the apps that allow you to customize calculations such as AppBuilder. This is needed as you must convert the water pressure to a distance (not the same as in the air obviously).
AllanOlesen67 +1. Not to take anything away from those that are having real problems with the altimeter/barometer/temp combo, many have no idea how it works and the complexity involved (especially staying accurate over a given period of time without calibration). I'm not saying Garmin does it the best, just that any abc watch will need to be calibrated on a regular basis as they drift. Even counting on GPS is not great given the lack of vertical accuracy (generally 1.5 to 2 x less than horizontal) - easy to be off by many meters even with a good fix.

Pitz and Kilt, the OP is asking about the watch's ability to record water depths.

Your replies are about an entirely different issue: Altitudes (in air) below sea level.

To Pitz, I further recommend that you read some of the many threads on altitude measurements. If you think that the watch is malfunctioning because it shows a negative altitude, you simply don't understand how a barometric altimeter works.

I know as a baro/gps altimeter works. I'm also curious about depth readings! DESCENT MK1 is is probably equipped with the same hardware of F5X!
What do you think about?

I wonder if there is cut-off for the ambient pressure reading. If there is no cut-off, a workaround could be using the built-in ambient pressure data field and do some simple math in the head while diving.

Each 100 millibar is equal to one meter, and the surface pressure will be around 1000 millibar (at least when diving in the ocean), so 1100 millibar = 1 meter, 1200 millibar = 2 meter, 1300 millibar = 3 meter, etc.

Pitz and Kilt, the OP is asking about the watch's ability to record water depths.

Your replies are about an entirely different issue: Altitudes (in air) below sea level.

To Pitz, I further recommend that you read some of the many threads on altitude measurements. If you think that the watch is malfunctioning because it shows a negative altitude, you simply don't understand how a barometric altimeter works.

Thanks for the obvious... I can read and am aware it's in relation to diving/ snorkeling. The title of the thread is "Negative Depth?" and so I was pointing out that the watch does record Negative Depth IE I was answering the question asked!... It matters not a jot if your above water or below water- it's a pressure sensor! trust me, I used to work in a Hyperbaric Chamber treating divers!

If your diving at high altitude (lakes etc) You need to calibrate your dive computers to that altitude before use.. so the two are intrinsically related.. as I said, the sensor cannot tell if its air, water or concrete pushing on it

Thanks for the obvious... I can read and am aware it's in relation to diving/ snorkeling. The title of the thread is "Negative Depth?" and so I was pointing out that the watch does record Negative Depth IE I was answering the question asked!... It matters not a jot if your above water or below water- it's a pressure sensor! trust me, I used to work in a Hyperbaric Chamber treating divers!

If you trained divers, I certainly hope that you know that the relation between pressure and altitude depth is entirely different in air and in water.

In air, 1 millibar of pressure change is equal to approx. 8 meter of altitude change (when you are near sea level).

In water, 1 millibar of pressure change is equal to approx. 1 cm of depth change.

That is a difference by a factor of 800.

In short: The fact that a watch can show negative altitude in air is absolutely no indication that it will be able to show true negative depth in water. If the watch just continues its air altitude calculation when it gets submerged to a depth of 1 meter, it will show an altitude of approx. -800 meter, not -1 meter.

AllanOlesen67

Apologies for the tone of my post. Happy to admit my errors and you are indeed correct, I knew it wasn't exactly the same although I had not appreciated quite the difference between the 2- I only nursed divers with decompression illness, not trained them or manage the chamber operations. Always happy to be corrected and learn from others. I should in my "post-night shift state"- have mentioned the relationship was not the same and for obvious reasons, the 5X should not be used in place of a dedicated dive computer- It was instead a rather clumsy way of highlighting the watch did display a negative value.

Apologies!

KP