Dive Planner: Inconsistent dive ceiling calculations

[Robert Helling]

Willem,

> On 2. Jan 2018, at 13:57, Willem Ferguson <willemferguson at zoology.up.ac.za> wrote:
> 
> Attached four files: a dive plan and three profiles.
> 
> 1) Load dive plan into Subsurface. This gives dive1_list.png.
> 
> 2) Open the dive plan for edit in the planner. This gives dive1_2.png. A totally different ceiling compared to previous representation.
> 
> 3) Delete all the dive points in the ascent phase of the dive plan. I used the Dive Points Table to delete the points. This gives dive1_3.png. Yet another ceiling totally different from previous representation.
> 
> We have three entirely different ceilings for the same dive plan.
> 
> I have no idea where the inconsistency arises.

reading your second mail, I understand there are only two different ceilings left: The one in the divelist which equals the one in the planner when you remove the ascent points and the second one you get in reedit until you remove the ascent waypoints.

This is a „feature“ of the VPM-B model: It treats the „decompression phase“ different from the bottom part of the dive, in particular it takes note of the ceiling at the beginning of the decompression. In the planner (as well as replan), we take all the explicitly listed waypoints as the definition of „bottom phase“ (so in replan before deleting the waypoints, the whole dive is „bottom phase“). In the divelist we make a clever guess (thanks to Rick’s code) as to where the bottom phase ends. This tends to be very close to the true bottom phase of planned dives (when the entered waypoints end at the deepest part of the dive and then the planner takes over and manages the ascent) but is not exactly the same.

I have recently blogged about this problem here

https://thetheoreticaldiver.org/wordpress/index.php/2017/12/22/vpm-b-for-real-dives-or-not/ <https://thetheoreticaldiver.org/wordpress/index.php/2017/12/22/vpm-b-for-real-dives-or-not/>

Best
Robert
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