GFlow specification in Preferences

[Robert C. Helling]

On 29 Jun 2014, at 09:02, Willem Ferguson <willemferguson at zoology.up.ac.za> wrote:

> In the Preferences panel, where GFLow and FGHigh are specified, there is a checkbox for "Use GFLow at max depth". The meaning of this checkbox is clear, but what is the effect on the calculations if this checkbox has NOT been activated? This is for user manual.

The difference is which depth the GFlow applies to: The deepest point of the dive (checkbox checked) or the depth of the first stop. The latter is what the original description on gradient factors by Baker specified and therefore I guess that is the setting that most people would want to use.

The problem with that setting is that early in the dive this is not really well defined (for example if there is no ceiling yet or the ceiling = first stop would be very shallow). But this influences only the ceiling shown in early parts of the dive.

Not as well that the deco does not look into the future: For the ceiling at any point in the dive it is actually the deepest point so far in the dive vs the deepest ceiling encountered so far in the dive. 

Does that make sense?

Re the planner chapter in the user manual:

A few points:

I would not differentiate between planning and evaluation especially since all that you list under evaluation is already available in the planner (in particular I would always turn on the display of ceilings in planner mode).

Also the advice to start with an empty dive list is not generally true: If you have loaded your actual dive list, the planner takes into account tissue saturation from previous dives. That is why the planner has a date and time selector to get the surface interval right. This way you can also plan multiple dives.

Furthermore, if you have a dive selected while entering the planner, the gases used in that dive are copied to the gas list of the planner. This is useful if you want to use the same set of gases again or it can be used to have standard sets of gases (like GUE people do): Just save a mock up dive that uses all the gases from the standard set and select that when entering the planner.

I think it should be pointed out that the dive can be specified both by mooing points in the profile and by entering values in the table.

The points in that  profile can also be moved using cursor keys.

The pO2 settings in the planner are there to provide default “switch to” depths for the deco gases. Those can be overwritten manually in the table.

The surface pressure can either be entered as a pressure or as an altitude (assuming 1013 bar at sea level). At least after Dirk applies my last patch.

In the logic of gradient factors, you are not supposed to manually enter deep stops (of course, you can). Use a low enough GFlow and the planner will plan those for you (that’s what GFlow is for: provide you with stops early in the ascent).

Maybe you should point out that the planner starts with the GF’s from the preferences. But changing GFs in the planner does not change those in the preferences (rather you can play around with them to see how they affect deco). So if you changed them, when back in dive log mode, the profile and its ceiling is plotted with GF’s from the preferences which means that the dive could violate the ceilings of other GF settings (i hope this point is not too confusing).

Maybe you should mention that you can print the deco plan for your wet notes. You can as well cut&past it to a word processor to adopt layout to your needs.

You don’t mention the dive note settings (and the many other settings like the various asent/descent rates). In fact, form your screen shots it seems you are not using a very recent version of master (a lot has changed recently).

Ah, important: the “segment duration” points in the notes include ascents to the stop depth unless “display transitions in deco is selected”. In particular for the first stop these can be several minutes. The time shown is not the stop time but rather the time to leave the stop measured from the time you left your last depth.

Hope that helps.

Best
Robert

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Robert C. Helling     Elite Master Course Theoretical and Mathematical Physics  
                      Scientific Coordinator                                   
                      Ludwig Maximilians Universitaet Muenchen, Dept. Physik    
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