Hi Willem, Your deduction of the colours is close. Most significant point is that the "offgassing" colours are relative to the M value (i.e. that used when GF = 100/100), rather than the specified gradient factors (or VPM-B conservatism). Making it relative to the M value makes it easier to compare different profiles using the same scale. E.g. comparison of deco profile with deep stops (e.g. GF 30/85 or VPM-B) vs no deep stops (e.g. GF = 80/80), which is what was done in the Simon Mitchell presentation.
On 4 October 2016 at 22:45, Willem Ferguson <[email protected] > wrote: > I did some measurements on the heat map after the latest release > (5.2-1640-gb3a0ab dated Oct 3rd) which I assume is the 4.6 beta release and > which incorporates Robert's latest patch. > > Attached two dives using the Buehlmann algorithm. The time difference > between events in the the heat map and those in the dive profile looks to > be more or less constant during a dive. In dive 1 (attached) the difference > is approx 100 seconds, while in dive 2 (attached) the difference is about > 65 seconds. However, in both dives the difference is close to 35 horizontal > pixels. > > With respect to the colours used in the heat map, I deduce the following: > > Light blue: Inert gas tissue pressure far below ambient inert gas > pressure and close to pressure when dive started. > technically the colour is cyan, but light blue is a good enough description > Dark blue: Some ongassing has occurred but tissue pressures still far > below ambient pressure. > not actually dark, but an intense blue > Purple: Tissue gas pressure approaches that of the ambient inert gas > pressure. > correct > Black: Tissue gas pressure roughly equal to ambient gas pressure. > actually at ambient pressure * fraction N2 in air, so equal to where you tissues end up breathing air on the surface Grey-green: Tissue gas pressure greater than, but close to ambient pressure. > actually about ambient pressure > Bright green: Tissue gas pressure significantly above ambient pressure but > below Gradient factor limit. Efficient offgassing is taking place in the > tissue groups in tissue slightly above ambient pressure: GF = 10% > green. > Green-yellow: Tissue gas pressure approximately at limit imposed by > gradient factor. > Yellow: Tissue gas pressure exceeds limit imposed by gradient > factor. > tissue at GF = 55% > Orange ? Approaching GF100 gas pressure ??? > Red ? Exceeding GF100 gas pressure ??? > tissue at GF = 100% Below ambient pressure, the value is the scaled from the ratio (inert tissue saturation) / (ambient pressure). Above ambient pressure, the value is relative to the M value The exact points on the colour scale are interpolated between points on the HSV (hue, saturation, value) colours scale Tissue pressure below ambient pressure points are: tissue pressure negligible relative to ambient pressure (rapid descent to depth): "bright" cyan (HSV = 180 deg, 1, 1) tissue pressure ~ 53% of (ambient pressure * fraction inert gas in air): "bright" blue (HSV = 240 deg, 1, 1) tissue pressure = 80% of (ambient pressure * fraction inert gas in air): "bright" purple (HSV = 270 deg, 1, 1) tissue pressure = (ambient pressure * fraction inert gas in air): black (HSV = 270 deg, 1, 0) <---- this is special because it is where your tissues end up if you breath air on the surface tissue pressure = ambient pressure: "medium" green (HSV = 270 deg, 1, 0.68) Tissue pressure above ambient pressure points relative to M value (tissue "gradient factor") are: 10% of M value = "bright" green (HSV = 120 deg, 1, 1) 55% of M value = "bright" yellow (HSV = 60 deg, 1, 1) 100% of M value = "bright" red (HSV = 0 deg, 1, 1) 140% of M value = white (HSV = 0 deg, 0, 1) I hope you never see the colours beyond red in an actual dive - but you can in a test plan if you set GF > 100%, or VPM-B with zero conservatism and a deco dive with a reasonably long bottom time, which can result in an equivalent GFhigh >100%. > In the user manual, I would like to but an example of the gas pressure > graph in the Information box next to the representation of the same instant > as a vertical slice through the heat map. In order to do that, one needs to > understand the colours. > That's a good idea. The colour graph and pressure graph in info box are calculated from the same variable. The equivalent points and colours in that graph are GF 100 (top line) = red in tissue plot (HSV = 0 deg, 1, 1) GF = 0 (inert gas equilibrium pressure) = "medium" green (HSV = 270 deg, 1, 0.68) base of graph = tissue pressure relative to ambient pressure negligible = cyan (HSV = 180 deg, 1, 1) Note that the variable being plotted in both cases is actually entry->percentages[j], which is on its own special scale, where 50 equates to zero gradient, and 100 equates to M value (c code copied below). In the descriptions above, I have back-calculated it to gradient factors and tissue pressure to ambient pressure ratio. From http://git.subsurface-divelog.org/?p=subsurface.git;a=blob;f=core/profile.c;h=935f95ede860ada68efa47d7c29f5af11601bda9;hb=HEAD#l1021 1021 for (j = 0; j < 16; j++) { 1022 double m_value = buehlmann_inertgas_a[j] + entry->ambpressure / buehlmann_inertgas_b[j]; 1023 entry->ceilings[j] = deco_allowed_depth(tolerated_by_tissue[j], surface_pressure, dive, 1); 1024 entry->percentages[j] = tissue_inertgas_saturation[j] < entry->ambpressure ? 1025 tissue_inertgas_saturation[j] / entry->ambpressure * AMB_PERCENTAGE : 1026 AMB_PERCENTAGE + (tissue_inertgas_saturation[j] - entry->ambpressure) / (m_value - entry->ambpressure) * (100.0 - AMB_PERCENTAGE); Regards,
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