User manual: Explanations for new UI additions

Robert C. Helling helling at
Sun Oct 5 09:45:46 PDT 2014

On 05 Oct 2014, at 17:16, Willem Ferguson <willemferguson at> wrote:


> I am lupdating the user manual contents. There are two new additions to the UI that I do not understand enough to generate appropriate text.
> 1) The "Shearwater-like" pressure information in the Info box on the dive profile. Robert, please give some info in telegram style?
> 2) The pressure graph at the bottom of the profile. Please give a bit of information? One can intuitively understand the green lines, but what are the blue, grey and black lines?

the two are supposed to show the same information, in the info box for one instant of time and the graph obviously shows it as a function of time. 1) is meant to be a clone of what you see in this video:

The info shown are the inert gas loadings of the separate tissues and even though it is calculated it is meant as qualitative display.

In 1) the tissues are the grey bars moving up, the fastest on the left and the slowest on the right. In 2) the faster tissues are greener while the slower ones are bluer.

The scale of the y-axis is twofold (as partial pressure mbars don’t mean much to people): If the partial pressure of the tissue is below the ambient pressure, the scale is the ambient pressure (the ambient pressure being the end of the green area in 1) and the grey line in 2). In 1), the inert gas pressure of the current breathing gas is indicated by the lower black line (below ambient pressure and thus in the green area). While you dive at constant depth, all tissues approach that line exponentially in time.

For partial pressures above ambient pressure, the scale for the over pressure is the maximally allowed overpressure according to vanilla Buehlmann (the beginning of the red area in 1) and not explicitly shown in 2). 

If you use gradient factors (other than 100/100), you only allow a depth dependent fraction of the allowed overpressure compared to Buehlmann (that is the percentage of the gradient factor). The applicable overpressure according to the gradient factor at the current depth is the upper black line in 1) and the thick black line in 2). If GFlow < GFhigh (as it is supposed to be) you will see this black line going up as you ascend.

As said above, at constant depth the tissues approach the inert gas pressure of the inhaled gas. As everything is plotted relative to ambient pressure (or M-value respectively), the tissue loadings go up on ascent while they go down on descent.

In deco (or when the planner takes care of the ascend), you ascend until the first tissue touches the gradient factor line. Then you wait until that tissue pressure has gone done so it is still below that line after ascending to the next stop depth.

Does that help?


Robert C. Helling     Elite Master Course Theoretical and Mathematical Physics  
                      Scientific Coordinator                                   
                      Ludwig Maximilians Universitaet Muenchen, Dept. Physik    
print "Just another   Phone: +49 89 2180-4523  Theresienstr. 39, rm. B339       
    stupid .sig\n"; 

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