Error in descent rate and ascent rate calculation

I have noticed incorrect ascent/descent/hang time/rates as well.  The math simply doesn't add up.   

If figured the probability I was the only one with this problem was near zero. Thanks for speaking up. Please encourage other freedivers with this watch to speak up as well. 

I have the descent G1, and on CWT the times seem to be close, but on FIM or CNF, rates and hang times are all over the place. Not sure how the calculation is done but seems to be the watch adds up little hang times between pulls/strokes… can this be fixed with a software update??? Would be very helpful as this is the information I was looking for when purchasing this watch

Hmm that actually makes sense. I wonder is Garnin is counting all of the “micro-hangs” that occur on when your hand is stroking through the water. Your hand would stay in one place as you propel yourself down the rope. If the computer counts those as hangs and adds then all up, it may make sense that the hang time for a touch and go Freedive in CNF or FIM would have non-zero hang times messing up the calculations. 

Garmin please look into this. 

post a graph showing the “microhangs” 

Yes Garmin PLEASE fix this issue! 

I've been in touch with Garmin support about this. They weren't aware of the problem but the product support rep I emailed back and forth with understood the issue. The accelerometer in the watch records hang time any time it isn't moving, as is the case during pulls in FIM with the arm the watch is on. These little hangs all get added to the "Hang Time" in the dive log summary. This throws off the descent and ascent times, and consequently, the descent and ascent rates. This makes the data useless for FIM dives. I haven't tested this for CNF. For CWT it shouldn't be an issue. According to the rep, the computer is performing as designed, so he couldn't create a ticket for it.

As I told the rep, this is a flaw in the software design. While the accelerometer is necessary to count steps or movement during sleep, I don't understand why it has to be engaged during a dive when we have two variables that are easily and accurately measured already - time and depth. With these two values, we can derive any information we need from a dive. So instead of movement - time and depth determine if there is any hang time. In other words, during a dive, if depth doesn't change and time passes, that's a hang. An example of this would be doing a hang during a warmup dive, or doing a deep hang at a target depth. 

This seems pretty straightforward to me, but admittedly I don't know what it takes to update software. In any event, it's something that needs to be changed. I suppose a workaround could be to put the watch on your neck weight or in your hood, but a watch is obviously designed to be worn on the wrist. Let's hope Garmin becomes aware of this and does something about it. 

Im surprised its the accelerometer thats used if thats the case there must be a cut off for movements that requires looking at the watch or other micro movements to separate from a deliberate movement? adding an alternative time and depth point of measurement wouldnt solve this issue because the wrist with the watch on would stay at the same depth until you released your hand for the next movement down, around the neck or an attachment to the chest would be the only way round this but it should still offer that as an alternative to the accelerometer, i imagine trying to edit out the accelerometer micro hangs above lowest depth would be complex and problematic

They should just add a configurable delay after which a constant pressure is acturally considered a hang, e.g. more than 2-3 seconds is a hang. Obvisously Garmin didn't have freedivers in scope when developing the devices. But as they try to get more into it, sponsoring major freediving events, they should put more focus on this and refine the freediving specific features :-D

I agree with the delay when the sensor picks up constant pressure. I suppose it could be configurable, although that would add another layer of complexity to your dive setup. I was thinking two seconds would be enough of a delay to avoid recording a hang during a pull. In any event, the accelerometer should be disabled in freedive mode. 

This is unrelated to this problem, but the only other issue I have with the app is the dive timeline (graph). Instead of starting at "time zero" the individual dive timelines start with the beginning of the surface interval for that dive (or end of the last dive). To me, this is useless. It makes more sense to start at the initiation of the descent of each dive so that you can see where you were at any point during the dive without having to do math. That is, unless there is a setting to change this that I haven't found

Which app and version are you using? For me (latest version Garmin dive on Android) it shows both the time of day and the time passed including surface interval. See screenshot. On the other hand, I don't have the overlay option shown in the screenshot above byYoFoKo

Also I can't see any way how to get a larger graph in widescreen ... Everything works different than in the main Garmin connect app.