Plan Dive -- thoughts

Mon Mar 2 22:15:36 PST 2015

> On 02 Mar 2015, at 22:01, Steve Butler <kg7je at comcast.net> wrote:
> 
> 
> On 03/02/2015 12:22 PM, Joakim Bygdell wrote:
>> 
>>> On 02 Mar 2015, at 5:51, Steve Butler <kg7je at comcast.net <mailto:kg7je at comcast.net>> wrote:
>>> 
>>> 
>>> On 02/27/2015 10:54 PM, Joakim Bygdell wrote:
>>>> 
>>>>> On 27 Feb 2015, at 21:23, Steve Butler <kg7je at comcast.net <mailto:kg7je at comcast.net>> wrote:
>>>>> 
>>>>> Now, as an OC rec diver (soon to have access to the 100-130 depths) I would not want to enter the ascent segments separate from spending time at a level on the way up in order to indicate to ascend at best rate.  Take this scenario:
>>>>> 
>>>>> Drop to 130 and hang there for 6 minutes (28% O2).
>>>>> Rise at 30'/m to 70 and hang there for 8 minutes on the ledge.
>>>>> Ascend at 30'/m to 40 (no wait as it is a transition to an upslope.
>>>>> Spend 5 minutes swimming the upslope to 15.
>>>>> Spend the standard 3 minute stop at 15.
>>>> As this is a multilevel dive you have to do some calculation on your own, i.e transition times between the levels.
>>> 
>>> That is what I was hoping to avoid.  Especially as we entice more newly certified OW and AOW divers to use Subsurface.  Use of the printed dive planner and the eRDP both assume the transition time is included in the "level" time.
>> 
>> That is because they assume that each level is represented by a square profile.
>> 
>> If we take your example dive in reverse creating a dive your students might be called upon to do.
>> Assuming you start from shore with a 7 min slow descent to 70’, spend 7 min @ 70’ followed by 5 min swim upslope to 15'.
>> 
>> How do you plan such a dive on the tools you mentioned?
>> Do you ignore the time not spent @ 70’ or do you calculate the average depth for those 12 min and use a square profile as a representation?
>> 
>> 
>> If you use subsurface in your classes, teach the students to use it properly the way it was designed, 
>> do not try to imitate how the eRDP works because subsurface can do a lot more.
>> 
> 
> In which case the check to drop to first depth (which combines the first two lines) is really not that useful at best and possibly misleading when looking at what was entered.  It led to my losing the 130 depth on a dive with a 70' ledge on the way up.
> 
> Entered (with check box off)
> 130 7
> 70 2
> 70 10
> 
> Noticed the profile and saw that I'd failed to check the drop box.  So clicked that first box and got:
> 70 9
> 70 10

At which point you should have started over by entering 130 7 7 in the first line.

> 
> Now, if I enter the original list with that box already checked and then uncheck it I get:
> 130 2
> 130 4
> 70 2
> 70 10
> 
> Which is what I should have entered in the first place (though I would have done 130 5 on the 2nd line).
> 
> Which makes me think that if we're going to enforce entering all way points, then the "drop to first depth" box really isn't that useful and in my case, while I an learning the interface, caused me to lose my initial depth line.

The way the “Drop to first depth” is designed is that it takes the data from line 2 and assumes that you drop like a stone to that depth.
If you look at how the plan looks like when it is initialised with the box unchecked, 
the first line represents your descent and that is the one that gets discarded when you check the box.

Maybe we need to clarify this in the manual a bit more.
* If you intend to use the “Drop to first depth” it should be checked before you start adding waypoints to your plan.
	This is only useful if you are diving from a boat or a place with deep water close to shore.
	If you start your dive from shore the box should be unchecked. Otherwise subsurface can’t do proper calculations for your long and shallow descent.

* Each line in the planner table is the position of a waypoint and represents the end of a segment.

Another thing you can do is to check the box for “Verbatim dive plan”.
Then there will be a description of you dive in plain text.

For your example dive it looks like this:
	Transition to 130 ft in 1:58 min - runtime 1:58 on EAN26
	Stay at 130 ft for 5:02 min - runtime 7:00 on EAN26
	Transition to 70 ft in 2:00 min - runtime 9:00 on EAN26
	Stay at 70 ft for 10:00 min - runtime 19:00 on EAN26
	Transition to 0 ft in 4:09 min - runtime 23:09 on EAN26

If you let the planner know which cylinder you are intending to use as well as your SAC 
(which subsurface can calculate for you if you add the cylinder size, start and end pressures of the dives that you import) 
you get this little treat at the bottom of the Dive plan details. 

Assuming AL80.

	Gas consumption:
	55cuft/2031psi of EAN26 (5cuft/197psi in planned ascent)

> 
>> 
>>>> 
>>>> Final Depth Duration Runtime
>>>> 130
>>>>                 2  2   descend
>>>> 130
>>>>                 6  8   level
>>>> 70
>>>>                 2  10   ascend
>>>> 70
>>>>                 6  16   level
>>>> 15
>>>>                 5  21   swim upslope
>>>> 15
>>>>                 3  24   stop
>>>> 
>>>> When you do that the ascent rates that you can set tin the lower left cornet of the planner will not be used.
>>>> The descent rate will be used only if you check “Drop to first depth”. And in this case it will replace the first two lines with this.
>>>> 
>>>> 130
>>>>                 8  8
>>>> 
>>>> Containing both the descent time and the time spent at 130’.
>>> 
>>> This is what the OW rec diver expects to enter.
>> 
>> See above.
>> 
>>>> 
>>>>> Oh, and option to pick between 15 or 20'.  I noticed only 20' was set as the last stop.
>>>> That is because the planner used 10’ increments in its internal calculations.
>>>> And the planner will only calculate what reamins on the ascent after your last waypoint.
>>> 
>>> OK.  How about another check box to "include 3 min safety stop at 15 feet" at the end of the dive.  At least that is what is being taught in PADI.
>> 
>> That might not be to hard to implement.
>> 
>>>> 
>>>> 
>>>> Compare how the planner works on your example vs. a blue water ascent profile.
>>>> The only thing entered into the planner is this line with “Drop to first depth” checked.
>>>> 
>>>> Final Depth Duration Runtime
>>>> 130
>>>>                 13  13
>>>> 
>>>> In this case the planner will tell you that the calculated ascent from 130ft, using the defined ascent rates, will take 7minutes.
>>>> 
>>>> 
>>>> 
>>>> Multilevel dives you have to define all waypoints for all the levels, until the start of the ascent that contains your safety stop.
>>>> In the first example if the upslope didn’t exist your last waypoint would be @ 70’ and the planner would calculate the ascent time to the surface.
>>>> Since you don’t have any deco obligation it will tell you that you can ascend to the surface using the defined ascent rates over a time of 4min.
>>>> 
>>> 
>>> Would still want the option to add 15' 3 min safe stop without having to calculate the ascent times.
>>>> /Jocke 
>>> 
>>> --Steve
>> 
>> /Jocke
>> 
> 

/Jocke

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