Feature request: CCR cave bailout function

[sailor]

Hello,

I'ld like to ask for the implementation of the CCR cave bailout function, available for MK2 / 2N, for my newly aquired nano ( and other hwOS tech computers ).
I'm still using this function with my old MK2 and enjoiýing it a lot.
Unfortunatly the right button works more and more harder on my MK2 and is almost not useable anymore with thick gloves.
Thats why I aquired a nano and like to replace my MK2.

For the readers not familiar with that function.
You can setup your emergency bailout SAC and the volume of your CCR bailout gas ( if desired minus a safety margin ).
During the CCR dive, the computer will permanently calculate the amount of gas required to exit the cave the same way you entered, based on the SAC, depth and time. And it will warn you when exceeding your bailout gas volume setting.

No other dive computer company offers this function. It is a unique HW Legacy OSTC function.
I would also welcome it a lot for my OSTC 4 ( and 5 users ) aswell.

Thanks a lot for considering, Reiner

[Ralph]

Hello,
i am not familiar with the cave B/O function on the older OSTC models, but for the recent HWOS Tech firmware there is a special version availabe that offers such a function. Please contact HW directly by email for a copy of this version. It is not widly tested yet and therefor only given out on request.
BR
Ralph

[sailor]

Dear Ralf,
I spoke to Matthias on the Boot exibition and the BO function Im asking for is not available for any recent HW computer.
He asked me to raise this request.
The present cave function is not related to BO, but allows to store waypoints.

CCR cave divers, speak up please.

BR, Reiner

[swissdiving]

[Thorsten]

Hello Reiner,

sounds like an usefull function. I am interested in some more details how you use it and what would be your expectations.
Does the function consider one bailout gas or all gases which are in the bailout list and marked as "deco"?

=> Will the answer "You most likely will get out" be enough => just taking the current dive profile and one bailout gas into account
or do you expect "Enough gas for a return including all deco stops and available gases" => consider profile, add stops and handle gas switches.

Cheers,
Thorsten

[Ralph]

Hello Reiner & all other interested in the Cave-Mode,
i have two good news for you:
1) Cave Mode also works in CCR and pSCR mode, the gas needs will then be computed in bail-out mode, i.e. on the OC gases available.
2) Cave Mode is included in the latest 3.33 HWOStech firmware.

How do i know?
for 2) : Matthias just confirmed this to me.
for 1) : i am the one who programmed it... :-))

I'll append a seperate post to this thread with the detailed description of the cave mode functionality.

[Ralph]

Supplemental Manual for the Cave Mode Function

The intended use of hwos Cave Mode is to monitor if the gases that are carried by the diver are sufficient to end the dive, especially taking into account the amount of gases that will be needed to finish decompression stops.

The Cave Mode function builds upon the fTTS calculation function in combination with gas needs calculation. It extents these functions by not calculating an open water vertical ascent, but by tracking back the whole depth profile of the dive and including final and/or intermediate deco stops that may become necessary. The cave mode function may be used in OC diving as well as in CCR/pSCR mode. When using it in CCR/pSCR mode, it will calculate the way back in bailout mode.

In order to produce accurate results, the user has to understand the following concepts and settings, and has to configure these settings with appropriate values:

• While on the way in, the depth profile will be sampled once every minute. For the return way calculation, it is assumed that the diver will travel at the same speed as on the way in and will travel along the same depth profile as on the way in.
  

  The cave mode provides capacity for 4 hours of depth profile recording. 10 minutes before storage capacity is exhausted (i.e. after 4 hours), an attention message will be given. When the storage capacity becomes fully used up, the cave mode function switches itself off and a respective warning is shown.

  If the cave mode function has switched itself off due to running out of storage capacity, it can be recovered on exiting the cave: When manually switching it on again, it comes back on again in turned state (see below), showing gas needs and TTS as of the position where it had switched off.

• Gas needs for the travel portions of the return way are calculated using the SAC work rate. While spending time on required deco stops, the SAC deco is used. Both SAC values, SAC work and SAC deco, need to be set by the diver to consumption rates that match personal rates, taking into account elevated rates due to stress etc.
  

  If actual SAC rate is higher than the configured on, or if traveling back slower than on the way in, the real needs will be under-estimated and the diver may run into an out-of-air situation if taking the dive to the limits!

• Every tank needs to be configured with its size and with the amount of pressure that is in it. The cave function will use these numbers to calculate how much gas will be available from each tank to be used for the way back.
  

  For tanks that is breathed from while on the way in, the tank pressures have to be set to the turn pressures that have been determined for the respective tanks during dive planning!

  The calculations are based on the laws of ideal gasses, i.e. the limited compressibility of real gasses ist NOT compensated for. So if a B/O cylinder is filled to 300 bar SPG reading, the OSTC tank pressure should not be set higher than about 270 bar (compressibility depends on mixture and is hard to calculate accurately, so use a safe-side rule-of-thumb value).

• While on the way in, the cave function constantly recalculates how much gas from each tank will be needed to exit the cave. Upon reaching 70% utilization on any tank, an attention message (color-coded in yellow) will be given. Upon reaching 100% utilization, a warning message (color-coded in red) will be issued. At the time a tank is calculated to be fully used up, the calculations will try to switch to another tank that still contains some gas according to the calculations. If such a tank exists, the remaining way out will be calculated based on this tank and hence on the gas in that tank, which may be sub-optimal in terms of decompression. If such a tank does not exist, the remaining gas needs will continue to be added on the depleted tank, resulting in displayed required tank pressure higher than configured pressure available.

• When turning the dive, i.e. upon starting on the way back out of the cave again, the cave function needs to be set into 'turned' state. This will stop the cave function to assume that the actual way out is still part of the way in and subsequently will stop taking further depth recordings and figuring them in for gas needs calculation.
  

  The diver shall turn the dive ultimately latest when any one of the gases calculates to be fully needed! In this situation, the diver will be without any reserves (based on all settings made and the limits of the cave mode of operation)! It is advised to set the tank pressures a bit lower than their actual fill pressure is and to also set the SAC rates a bit higher, to put the calculation results towards the safe side.

• When setting the dive as 'turned', the indicated gas needs are likely to still rise. This will be due to the fact that the cave function still calculates the gas needs for all the way back from turn point to the surface, not knowing how much of this way has been traveled already. In consequence, the tissue saturations that are gained on the portion of the way back that has already been traveled are calculated twice, resulting in an increased estimated deco obligation at the end of the dive. This effect can be overcome by using 'waypoints' (see below).
  

  Without having set at least one waypoint (see below) before setting the dive as turned, it is not possible to revoke the 'turned' state again!

• When the cave mode is switched off, the gas needs calculation reverts to the open water vertical ascent mode, that is no dedicated time for horizontal movement is figured in any more. Still, horizontal movements (further swimming out of the cave) can be done in parallel with doing decompression stops without requiring dedicated extra time in the calculations.
  

  When being back near the cave entrance, with only final decompression stops remaining to be done, and with the remaining way being doable while doing the decompression stops, it is appropriate to switch off the cave mode.

  The cave mode function can be switched off and on again at any time of the dive.Temporary switching off the cave mode while the dive is not set as turned yet can be used to pause the recording, e.g. while undertaking some tasks that take time on the way in, but not while on the way out, like fixing a line or doing survey or photography tasks.

• To tell the cave mode calculations where the diver is while on the way out, waypoints can be set while on the way in. Initially on setting the dive as turned, the gas needs for the full way back are calculated. Then the diver can select one of the waypoints and the cave mode function will calculate how much gas will be needed to return from this waypoint. Upon physically reaching the respective waypoint, indicated gas needs shall be accurate again for this position in the cave.
  

  Waypoints should be set at regular distances and/or important features in the cave profile, e.g. at places where intermediate deco stops are expected. While on the way back out of the cave, whenever a waypoint is reached the cave function shall be updated to this waypoint. This way the indicated gas needs will always stay near the expected real needs, but on the safe side, given that the conditions discussed above are met.

  The cave mode function provides for a maximum of 30 waypoints. Every waypoint that is set reduces the available depth profile storage capacity by the equivalent of four minutes of depth profile recording time. When all 30 waypoints are used, the depth profile storage capacity reduces to 2 hours for the inwards part of the dive.

  To establish relation between the numbering of the waypoints within the cave mode function and their physical positions in the cave, it is recommended to place cookies on the main line that are marked with the respective waypoint numbers.

  Every time a waypoint is set, a marker will be set in the normal logbook recording.

• If at least one waypoint has been set, the 'turned' state of the dive can be revoked again. To revoke the turned state and thus continue the dive in inward direction, the diver has to go back to a waypoint and select that waypoint in the cave mode function.
  

  The turned state can not be revoked while still being at the original turn point of the dive. The diver has to go back to a dedicated waypoint and restart from there.

  When the 'turned' state is revoked, the depth profile recording resumes right after the selected waypoint.
  

  The depth profile and all waypoints that were originally recorded after the waypoint from which the dive is continued again in inward direction are lost. The respective recording space will be freed up and used for the recording of the new sortie.

  This feature can e.g. be used for exploring different branches of a cave:
  
  1) set a waypoint at the forking point of the branches,
  2) explore the first branch (further waypoints may be set),
  3) when done, set the dive as turned,
  4) return to the forking point,
  5) recall the respective waypoint that was set at the forking point,
  6) select 'continue' to revoke the turned state and start the recording for the next branch to be explored now.

• The cave mode function can account for gases that are temporary unavailable because their tanks have been staged. On page two of the dive menu item 'Gaslist', tanks can be toggled between available (white), staged (disabled color and "S" marking for staged), and lost (disabled color and "x" marking aka crossed-out).
  
  If a tank is set to lost state, it will not be considered in deco as well as gas needs calculation any more. This state is revocable.
  
  If a tank is set to staged state, it will currently not be considered any more, but: Whenever a waypoint is set, a snapshot of the staged / not staged state of all tanks is taken. When the cave mode function works it way through the stored cave profile recording and hits a waypoint entry, it extracts this snapshots again and continues choosing gases for deco and gas needs calculation based on these snapshots.
  

  When staging a tank:
  
  1) Set a waypoint
  
  Within this waypoint the tank will be recorded as (still) being available, that is it will be available (again) for the calculations upon passing this waypoint on the way out.
  
  2) Set the tank as staged
  
  This will set the tank as being not available during the portion of the dive that lies to the cave-inside of the above waypoint.

  While a tank is set as staged, no 'better gas' cue will be generated for it.

  When a tank is picked up again, it needs to be set to available state again in order to positively confirm that it really is available again!

  When diving in OC mode or when in bailout mode, on selecting a gas that is set as staged it is automatically reverted to available state. The same holds true for gases that were declared as lost: on selecting them, they are also reverted to the available state again.
  

  When diving in CCR or pSCR mode and initiating a bailout, the dive will be automatically set to turned state (given cave mode is switched on and the dive is not already turned)!

Operating the Cave Mode Function:

To activate Cave Mode, start the Surface Menu and then go to "Dive Setup", "Dive Setup" (again), "Cave Mode" and set it to 'on'. Once Cave Mode has
been switched on via the menu, all dives will start in Cave Mode. The Cave Mode can be switched off during the dive (and on again), but it will not be possible the activate the Cave Mode after the dive has been started if it wasn't activated via the surface menu before.

During the dive, all Cave Mode operations are done via a dedicated Cave Mode menu. This menu can be accessed via the left button: after pressing left button for 'Menu?', press it again to show up 'Cave?', then press the right button to enter the Cave Mode menu. In OC mode, the cave mode menu is also reachable via the main dive menu, using the menu item 'Cave Mode'.

Depending on the 'dive turned' state, certain menu items are available or not. This will be indicated by the color coding of the respective menu items.

When the cave mode menu is active, the custom view is temporary replaced by a graphical representation of the waypoint situation. The last waypoint placed is shown in the middle of the display. The "-|" symbol depicts the end of the line, representing the deepest penetration point during the dive. The green arrow shows for which position the return gas needs are calculated.

In the message field, either a "cTTS xx'" or "WPyy xx'" is shown. While the dive is not turned yet, cTTS (Cave Time-to-Surface) is shown, with xx being the total time in minutes required for swimming all the way back and doing the decompression stops. When the dive is turned, WP is shown to indicate that the TTS is computed from off the waypoint yy. If yy reads the symbol -|, TTS is computed from off the turn point of the dive.

Last but not least: plan your dive and dive your plan! Do not soley base any cave dive on the calculations of your dive computer! The intended use of the Dive Mode Function is to provide a means to cross-check your actual dive with your plan, and to provide you with data helping decision making in case of an unforseen emergency situation.