Please Explain Future TTS Reading

[Divert]

Hello As I understand TTS is (Time to Surface including all deco stops) which is composed of two elements:
1.- Vertical Travel time at 10meters / min
2.- All Deco Stops.

Future TTS is nothing more than a TTS forcast if you stay X amount of time at your current depth.

Here I was sitting at 15m No deco obligation and the computer shows a TTS of 2' (i guess it takes 15m /10 m/min = 1.5 minutes and rounds it up to 2)

I have two questions:
1.- If there is no deco obligation, and I stay at 15m for 5 more minutes, and that does not create deco obligation, shouldn't Future TTS stay in 2 but not Zero!?

0 TTS means I have no deco obligation and I am at least less than 5 meters from the surface (if OSTC4 is rounding)

2.- I was expecting to see a NDL number instead of a TTS if I no longer have a Deco Obligation.

Thanks in advance
Humberto.

[Divert]

@heinrichsweikamp any coments on this?

Please.

Regards Divert

[Thorsten]

Hi Humberto,

I guess you had some deco obligation during the dive? As you metioned correct otherwise you would see the NDL.
I think what you see is the situation when you have less than 1 minute deco time. In that case no stops are visible but the TTS is still displayed because the deco seconds are > 0.

Regarding the futureTTS: I had a look in simulator mode and in case of a TTS of 8minutes the futureTTS showed 3minutes what from my point of view makes sence. For Deco calculation an ascend is simulated. In your example the simulated diver has already finished his dive.

Kind regards,
Thorsten

[Divert]

Thorsten Thanks for your reply!

Hi Humberto,

I guess you had some deco obligation during the dive?

Yes I had a few moments in Deco during the dive. And your explanation makes total sense.

Regarding the futureTTS: I had a look in simulator mode and in case of a TTS of 8minutes the futureTTS showed 3minutes what from my point of view makes sence. For Deco calculation an ascend is simulated. In your example the simulated diver has already finished his dive.

Kind regards,
Thorsten

How can TTS ever be 0 if you are sitting at 15m depth?
I understand that for TTS an ascent is simulated, but only after sitting at the current level of 15m for the preset time, (5 minutes in this case)
It could never be less than 1:30 seconds (if ascent rate is 10 m/min)
Since TTS = Travel Time to Surface + All Deco time I belive there is something wrong there.

[Thorsten]

Well from decompression calculation point of view the behavior is correct. If the exposure of gases is not adding decompression time at the depth you are (15m in this case) then the answer to the question where is the diver in 5 minutes is: "on the surface".
But I see your point: when I am on 15 meter and the tts is 2 minutes then the tts should be still 2 minutes if I stay there for another 5 minutes.
I think such kind of discussion have been there before and I belive most divers are trying to avoid to ascend from 15m to surface in 2 minutes or less => what is the added value of the tts in this case?
Most likely that is the reason why the current tts view is returning to the NDL display.

=> I see a possible improvment: hide the futureTTS in case it is 0 or as alternativ smaller than the current tts. Similar to the view handling already implemented for the current tts.

[Divert]

Thorsten, thanks for your answer!

Well from decompression calculation point of view the behavior is correct. If the exposure of gases is not adding decompression time at the depth you are (15m in this case) then the answer to the question where is the diver in 5 minutes is: "on the surface".

Please forgive me if I am being stubborn but:
The diver is not at the surface!, according to the definition below taken from the manual (... If you will stay on the actual depth for some more minutes...) , in 5 minutes he would NOT be on the surface but rather at 15m (by definition) and time to surface from 15m depth is never 0, but actually 1:30 if and only if staying 5 more minutes at 15m did not made me incur in Deco time, otherwise it would be 1:30 + whatever deco time I need to do.

Fragment of the OSTC4 Manual:

So I still belive there is something wrong.

Please advice.

[Thorsten]

Well, it is like it is written in the manual: a deco forecast. If there is no deco time then the result is zero.
If a futureTTS considering the time needed to get to the surface would be added (use case no deco pending) then the behavior compared to the visualization of the current deco would be changed (no deco => NDL displayed). OK let's be consequent and add this calculation to current and futureTTS calculation... I think divers which do not follow the discussion in this thread will ask "Where the... is the NDL?" and of course the manual would have to be adapted...

=> I think hiding the futureTTS in case no deco is pending is the better solution.

By the way: the ascend speed coloring of the depth display is progressing good.

Cheers,
Thorsten

[Divert]

Thanks for the explanation.

By the way: the ascend speed coloring of the depth display is progressing good.

This is so awesome! I can't wait to have it on my OSTC4 Thank you all for the hard work.

[Matrixli]

I ran into something similar and found out the issue was tied to how my GF was configured. After rechecking the gradient and making sure the dwell time was long enough, the values started matching up better. Also, someone on Trusted Psychics mentioned a related workaround for a different model, which made me look at my settings from a new angle—helped a lot.