Muy buenas,
A ver, ya que estamos (https://viviendoapesardelacrisis.blogspot.com/2023/05/shearwater-teric-swift-smart-ai.html):
https://en.wikipedia.org/wiki/Albert_A._B%C3%BChlmann
https://en.wikipedia.org/wiki/B%C3%BChlmann_decompression_algorithm
ZH-L 16 (1986):
-ZH-L 16 or ZH-L 16 A (air, nitrox): The experimental set of parameters published in 1986.
-ZH-L 16 B (air, nitrox): The set of parameters modified for printed dive table production, using slightly more conservative “a” values for tissue compartments #6, 7, 8 and 13.
-ZH-L 16 C (air, nitrox): The set of parameters with more conservative “a” values for tissue compartments #5 to 15. For use in dive computers.
-ZH-L 16 (helium): The set of parameters for use with helium.
-ZH-L 16 ADT MB: set of parameters and specific algorithm used by Uwatec for their trimix-enabled computers. Modified in the middle compartments from the original ZHL-C, is adaptive to diver workload and includes Profile-Determined Intermediate Stops. Profile modification is by means of "MB Levels", personal option conservatism settings, which are not defined in the manual.
Velocidad de ascenso:
Ascent rates:
Ascent rate is intrinsically a variable, and may be selected by the programmer or user for table generation or simulations, and measured as real-time input in dive computer applications.
The rate of ascent to the first stop is limited to 3 bar per minute for compartments 1 to 5, 2 bar per minute for compartments 6 and 7, and 1 bar per minute for compartments 8 to 16. Chamber decompression may be continuous, or if stops are preferred they may be done at intervals of 1 or 3 m.
Gradient Factors:
Gradient factors (GF):
Gradient factors are a calculation trick (Erik C. Baker) that consists of taking a percentage of each M-Value (e.g. 90%) in order to increase conservatism (shorter duration without mandatory stops, longer and/or deeper stops) by reducing the maximum amount of neutral (inert) gas (e.g. nitrogen) accepted when approaching the surface (Maximum Value of each tissue compartment at... 9 m, 6 m, 3 m, surface).
It is generally possible to define two GFs: GFlow and GFhigh. GFlow applies to the first (deepest) stop, GFhigh to the last stop (closest to the surface). Any intermediate GFs (between GFlow and GFhigh) are calculated by linear interpolation.
For dives without mandatory stops, only GFhigh is used, even if a GFlow is defined.
Twin GFs (e.g. 80/80) have the same effect as artificially increasing dive time (the time taken into account is greater than the actual time). When using printed dive tables, it is like an "impromptu addition of extra increments of depth and time beyond those actually required by the dive, universally known as Jesus-factoring".
Asymmetric GFs (e.g. 30/70) can be used to force deep stops. Deep stops can be defined as follows: “one or more voluntary or empirically derived decompression stops that are deeper than any prescribed by the algorithm utilized”.[21]
GFs can be implemented in dive computers in three ways:
-with a preset mode (e.g. L0, L1, L2 ... or P0, P1, P2 ...) corresponding to a decreasing pair of GFs: 90/90; 85/85; 80/80... ;
-leaving GFlow and GFhigh free for input;
-by including in the algorithm a modification of the GFs according to the diver's behaviour (profile, ascent speed, etc.).
In all cases, the choice of GF values is arbitrary.
The term "ZH-L 16 with GF" is misleading. It may give the impression that there is a specific set of parameters for use with GFs. There isn't. Any set of parameters with M-Values (ZH-L, US-Navy, Hahn, RGBM, Comex...) can be used with GF.
Shearwater:
https://www.shearwater.com/wp-content/uploads/2012/08/Shearwater-GF-V3.pdf
Garmin:
https://www.garmin.com/en-US/garmin-technology/dive-science/In-dive-features/buhlmann/
Suunto:
Validation of algorithms used in commercial off-the-shelf dive computer:
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6355308/
Introduction:
Whilst the US Navy has been very systematic about validating Navy dive computer algorithms, there has been little documented or published evidence of rigorous testing of the algorithms in commercial off-the-shelf dive computers. This paper reports the evaluation of four algorithms used in these − Bühlmann ZHL-16C; VPM-B; Suunto-RGBM; EMC-20H − by comparison with US Navy experimental dives with known decompression sickness outcomes.
Methods:
Three specific tests were developed to test the algorithms' ability to mitigate decompression sickness: Total decompression time; no stop times and first stop depth. Output of commercial decompression algorithms were compared to either the probability of decompression sickness (PDCS) results from US Navy man-trials or statistical models derived from PDCS data. The algorithms were first tested with default conservative factors, then these factors were adjusted if the tests were not initially passed. The last verification step was to compare the output of the wrist computer with that of the full desktop algorithm.
Results:
This testing indicated that, whilst none of the four passed all of the proposed tests with factory-default conservatism, ZHL-16C and Suunto-RGBM could be made to pass by adjusting user-defined settings.
OVERALL ASSESSMENT:
The assessment results are summarised in Table 3. Based on an initial analysis, it can be inferred reasonably that none of the four algorithms evaluated passed all of the tests with default settings. ZHL-16C could be adjusted to pass all of the tests with GF-Hi < = 70 and GF-Lo > = 55. Suunto-RGBM could be made to pass all of the tests by simply turning off the deep stop option, which is easily done on the wrist unit tested. VPM-B could be adjusted to prescribe sufficient TDT (the required conservatism factor depends on the depth-bottom time of the dive) but could not be adjusted to pass the first significant stop test; the first stop was always too deep. EMC-20H could be tuned to pass the TDT test (conservatism ∼ 50%) and the first stop test (conservatism < 5%) independently, but not simultaneously.
Nota: Mi idea para tocar los GFs por defecto del Teric:
58/70 para Tec y 70/85 para Rec.
Me cuadra (otra vez).
P.D: https://viviendoapesardelacrisis.blogspot.com/2020/11/algoritmo-rgbm-reduced-gradient-bubble.html
P.D.2: Relojes?
https://watchangels.ch/en/watches/
Actualización a 21/05/2024: Vaya! Iba a ir hoy pero se ha cancelado por falta de interesad@s:
https://viviendoapesardelacrisis.blogspot.com/2013/06/charlas-tematicas-en-buceo-donosti.html
https://viviendoapesardelacrisis.blogspot.com/2023/05/shearwater-teric-swift-smart-ai.html
Actualización a 17/07/2024: Finalmente se hizo y le mandé un correo para el que sigo esperando respuesta.
A ver:
Actualización a 20/11/2024: Garmin Descent X50i:
Actualización a 03/01/2025: Ok, página 144. Gradient Factors:
Values of GF(Lo) from 5% to 35% are used together with values for GF(Hi) ranging from 70% up to 150%.
https://viviendoapesardelacrisis.blogspot.com/2014/08/deco-for-divers-divers-guide-to.html
https://viviendoapesardelacrisis.blogspot.com/2023/05/shearwater-teric-swift-smart-ai.html
Frente a lo que personalicé yo:
OC Tec: De 30/70 a 58/70.
OC Rec: De 40/85 a 70/85.
Los GF(Lo)s del libro son bajos (5-35?) y los GF (Hi)s altos (70-150?). Aunque también es verdad que habla de hacer paradas más profundas y anticipadas para poder terminar las inmersiones de forma más agresiva.
Actualización a 16/09/2025: A ver...
https://viviendoapesardelacrisis.blogspot.com/2019/10/inmersiones-con-descompresion.html
Notas sobre una inmersión profunda con Trimix:
https://viviendoapesardelacrisis.blogspot.com/2023/11/inmersiones-profundas.html
-TTS antes del ascenso:
-Ajuste de presión parcial de oxígeno para acelerar la deco:
-Después del tratamiento: 3 semanas sin bucear y no volver al buceo profundo.
-Conclusiones: PIENSA que aleteo mucho en el fondo por no encontrar el pecio y no usar scooter y fue un error no avisar del frío en una de las piernas (aunque sí lo hizo con el dolor abdominal que asoció a lo que comió y resultó ser un Spinal bend DCS) durante el ascenso y le queda la duda de si una parada profunda habría solucionado el problema.
https://viviendoapesardelacrisis.blogspot.com/2013/10/velocidad-de-ascenso-lenta-vs-ideal.html
-Discusión sobre los GFs en los comentarios:
-Sobre el dolor abdominal:
Actualización a 23/09/2025: El Tigre me pregunta por los GFs de su Mares Puck 4:
https://www.mares.com/es_ES/puck-4-414149
https://cdn-mdb.head.com/PDM/download/593110-qttudfegx3k8g04w
https://www.mares.com/es_ES/sports/diving/gradientfactor/
Dive computer decompression models and algorithms: philosophical and practical views
Product No: ARTICLE-01
This paper outlines models and algorithms in general, and then discusses gradient factors in further detail.
By Sergio Angelini - Chief Technology Officer, Mares
https://media.head.com/_11__/documents/DL/324321-eo4n9nvm8nww0s0k
Y a ver si veo lo de la gráfica que me enseñaba:
Parece que no.
Nota: Interesante comparativa de GFs por fabricante:
https://scubaboard.com/community/threads/gradient-factor-presets-by-manufacturer-computer.576330/
Y artículo sobre funcionalidades de los ordenadores con GFs (Shearwater):
https://shearwater.com/blogs/community/evolution-of-dive-planning
The @+5 option is particularly useful. It shows what the TTS will be in 5 minutes, assuming the diver stays at the same depth. This can be used for looking ahead. If you know your maximum TTS, then you can compare this against your current TTS to see if you have reached your limit, but the @+5 setting allows you to look ahead 5 minutes and see what your TTS will be in the future. You can use this to decide whether you have time to look at another piece of the wreck or whether you must turn around and head back to the shot-line. This is particularly important at deeper depths where the rate at which decompression is built up is much faster, and a large amount of deco can be incurred in a relatively short period of time.
The Δ +5 option shows the difference (the delta or Δ) between your TTS right now and what your TTS will be in 5 minutes. For example, if your TTS is 20 mins and your @+5 is 30 minutes then the Δ +5 would be 10 minutes (30 – 20 = 10). In other words, in 5 minutes time, you will have incurred an additional 10 minutes of deco more than you have right now. This could be done manually, but in some situations, it is nice to be able to see the delta without having to constantly make that calculation. The size and magnitude of this figure can also be used to tell the current state of your decompression. If the Δ +5 is positive, this means that you are on-gassing and will have more decompression in 5 minutes than you have right now. If Δ +5 is 0, then you are neither ongassing or offgassing and you will have the same amount of decompression in 5 minutes as you have right now. Finally, if the number is negative then you are offgassing and you will have less decompression in 5 minutes than you have right now. This is particularly useful for multi-level dives. Let’s assume you are on a deep reef and you notice that your TTS is approaching your maximum TTS. You ascend a few metres and you notice that your Δ +5 is now +1. This means that you are still incurring additional decompression, although at a much slower rate, and so your TTS will continue to increase. If you come up a few metres more, you can now see that your Δ +5 is zero. This means that you are neither ongassing or offgassing and you can stay at this depth without increasing your TTS. If you ascend slightly shallower and your Δ +5 changes to -1 then you can see that you are now offgassing and you can stay at this depth almost indefinitely as your TTS will slowly reduce.
The settings above can be used to proactively manage the dive and can be used on any dive. There are several other options that would primarily be used in an emergency to change some of the dive parameters on the fly.
The CEIL option shows the raw decompression ceiling. Once the diver goes into decompression, they can no longer ascend directly to the surface, and there is a depth at which the supersaturation would exceed the maximum allowed. The decompression ceiling is the exact depth at which this would occur. This is slightly different from the decompression stops shown on the computer as the deco stops are rounded to the nearest 3m increment below the actual decompression ceiling. The actual value of the ceiling will slowly get shallower during the decompression, but the decompression stops will stay at the 3m increment until the ceiling reaches the next 3m increment. At this point, the decompressions stop will jump up to the next 3m increment. By comparing the decompression stop and the CEIL value you can see how much margin for error you have at that stop or how close you are to the end of the decompression stop. If your computer shows a 9m stop and your CEIL is 8.9m then you can see that the ceiling is only slightly above the current decompression stop and so there is very little margin for error in your position in the water column, and you also know that you will be at 9m for some time to come. As the CEIL moves up and gets to 8m then 7m and then 6.5m you know that your decompression stop is coming to an end. This can be useful to know if, for example, you are decompressing on a line at 9m along with a number of other divers. If it is getting crowded on the line at the 9m stop, but you know your CEIL is showing 6.5m then you can move up to 8m or 7m without breaking your ceiling. Your computer will alert you that you are above your decompression stop, and if you stay at that depth, it will give you a MISSED DECO alarm but you know that despite this you are in fact below your decompression ceiling.
The next setting that it is possible to select in the NDL space is the GF99 setting. This is useful information to know as it shows the current GF, in other words, how close you are to the M-Value which corresponds to a gradient factor of 99. Whether a diver selects his own gradient factor settings or makes the decision to use the default settings, the computer will display the ceiling, decompression stops, as well as the time to surface, based on these gradient factors. If the diver is using 30/80 gradient factors, then during the ascent up to the first stop the GF99 should be approaching 30, as the first stop is calculated as being at the point where the GF is at 30% of the M-Value. At the surface, the GF99 will be 80, as the high GF determines how close the diver is to the M-Value on surfacing so a GF Hi of 80 means the diver should be at 80% of the M-Value as they surface. For intermediate decompression stops, the GF99 will slowly increase from 30 on arrival at each subsequent stop. During each deco stop, the GF99 should slowly decrease as the tissues offgass and the ceiling increases. Once the stop clears and the diver moves up to the next stop, the GF99 will again increase. This allows the diver to “see” the offgassing taking place as it shows that as they offgass, the level of supersaturation is dropping, and they are moving further away from the M-Value.
If the GF99 is much lower than 30 on the initial part of the ascent or does not slowly increase on the ascent up to each subsequent stop, then the diver is ascending slower than intended. The TTS shown assumes the diver will be ascending at the prescribed ascent rate. If the diver is ascending slower than the correct ascent rate or stops below the decompression stops, then they are, in effect, lagging behind the calculated decompression schedule. The result of this is that the diver is not offgassing as quickly as the model has assumed, and so the diver will take longer to decompress. In extreme cases, the diver may still be ongassing in some tissues, and the slow ascent may actually increase the decompression requirement. As a result, the actual ascent time may be considerably longer than the calculated TTS. If the diver is using the calculated TTS to manage their dive as described above, this can cause a problem as the gas planning assumed that they would be following the calculated decompression schedule. By causing additional decompression time, they will end up requiring additional gas for this extra time.
If the diver ascends above the deco stop, the computer will give a warning. As we have already seen, you can ascend above this deco stop, but still, stay below your decompression ceiling as shown with the CEIL display. If you ascend even further beyond the CEIL depth, the GF99 can be used to provide some additional information. For example, if the diver has set a GF Lo of 30% and ascends above their initial deco ceiling, the computer will give a warning. The GF99 may still show that they are only at 40% GF which, although it is beyond both their deco stop and deco ceiling, is still well within the M-Value. Similarly, for the later stops, if the diver has set a conservative GF Hi of 70% and ascends above their deco stop, the computer will give a warning. The GF99 may still show that they are at 80% GF which is still well within the M-Value. However, if the GF99 shows more than 100%, the diver is now well over their M-value and is in a much riskier position.
The same goal can partly be achieved in the Dive Settings menu where it is possible to change the high gradient factor during the dive. By changing the high gradient factor from, say 70 to 80, you would reduce the rest of the remaining decompression. Although it is possible to change the high gradient factor in this way, it is not possible to change the low gradient factor, and so the initial stops would be unchanged.
This functionality is not intended to be used on a regular basis, and the diver should stay within the ceilings indicated. However, in an emergency, this functionality may be very helpful. For example, assume that a diver on a decompression dive is running low on gas. Their computer tells them that they have another 5 minutes of decompression to do before they can move up to the next decompression stop where there is more gas available. They could edge up from the current stop to the next stop while watching their GF99 setting. Even though they are breaking their decompression ceiling they can use the GF99 display to show them how close they are getting to their M-Value, and can then make an educated decision on what is the more important risk.
These last few options may seem worrying, or even dangerous, but remember that the stops are determined by the gradient factor settings. If you are using a GF of 70 then you may have a deco stop which would not be present if you had selected a GF of 80. So, missing a deco stop using a 70 GF, but still staying less than 80 on the GF99 display is equivalent to staying within the deco stops on a GF setting of 80%. In fact, you may have deco stops, while the underlying Buhlmann model, which is based on a maximum gradient factor of 99, may indicate that it is within the No Decompression Limit. This is completely normal for the first few minutes of going into deco. If you have your GF settings set to anything less than the maximum value of 99%, then a GF profile will always go into deco before the underlying Buhlmann NDL limit is reached.
The same approach could be adopted with ascending all the way to the surface. In a critical emergency, the diver could edge up towards the surface watching their GF99 display and making sure that they stay close to, but not exceeding, their M-Value. However, this case can be managed more effectively using the Surfacing GF display feature. This is a newer feature, and may not be available on your computer unless you have updated the software recently. The Surfacing GF displays the GF that you would get if you were to ascend directly to the surface right now, without doing any stops.
If the SurfGF display shows 50, this means that if you were to ascend to the surface directly, your maximum tissue saturation would be 50% of the M-Value. I.e. well within your M-Value limit with almost no chance of DCS. If your SurfGF shows 150%, this means that a direct ascent to the surface would put you at 150% of your limit, and well over the M-Value limit with a very high chance of DCS. Finally, if your SurfGF shows 99, then a direct ascent to the surface would put you right on your M-Value limit and is equivalent to the NDL limit of a straight Buhlmann model. Interestingly, you can be in deco but still have a SurfGF of less than 99. Remember that the deco stops are based on your selected GFs. If you have the default GF setting of 30/70, then you will start to get deco stops well before you reach the underlying NDL limit. So, if you have 5 minutes of deco shown on your computer but your SurfGF is 90 this means that you have 5 minutes of “GF Deco”, but you have not yet reached the NDL of the underlying Buhlmann model. This means that, in an emergency, you could still go straight to the surface without breaking the Buhlmann decompression schedule. This is very different from the situation where you have 15 minutes of deco and your SurfGF display shows 120. In this case, you have “GF Deco” as well as “Buhlmann Deco”. If you were to go straight to the surface, you would not only miss the deco stops indicated on the computer, but would also end up being over your M-Value on the surface and have a significant risk of DCI.
The SurfGF feature can be used at any point of the dive, not just at the start of the ascent. For example, you can track your SurfGF during your ascent and deco. Once your SurfGF drops below 99, you know that from that point onwards if there is an emergency, you could go to the surface and still be within the Buhlmann limits. Equally, you can use it the other way around. After your deco stops have cleared, you can monitor the SurfGF to see your updated SurfGF. One technique that can be used is to have a slightly more aggressive high GF such as 80 or 90 to reduce the mandatory decompression stops but then wait until the SurfGF has dropped to a lower level as a “safety stop”.
As the tools available to divers continue to change and improve, it is inevitable that the techniques used must also change to make the most of the available tools. This article is intended to show that, far from removing the need to plan a dive, the sophisticated dive computers available today can help to improve the planning process. They can be used to provide a more realistic and more flexible planning tool. They can also be used to adapt the plan when the situation changes. This is only possible if the diver understands the tools they have at their disposal and practices using them. After reading and digesting the information contained in this article, I would encourage you to make sure you know where to find the various display options on your computer. On your next dive look at the SurfGF value during the dive and watch the relationship between it and the NDL value. During the NDL ascent, look at the GF99 and SurfGF values. Then on a decompression dive, compare the CEIL and Stop Depth values as well as comparing the CEIL, GF99, and SurfGF values. It is essential that you understand all of the information in this article and practice it before using it to plan your dive or modify your dive plan. Like any tool, you must practice before using them for real. However, a bit of investment in time and practice will give you the ability to manage your ascent in a much more intelligent way than blindly following your computer or a fixed set of deco tables.
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Written by Mark Powell
Yes:
https://viviendoapesardelacrisis.blogspot.com/2014/08/deco-for-divers-divers-guide-to.html
Actualización a 25/09/2025: Y se lo he explicado con este gráfico:
Lo que configuramos son los escalones de la línea azul (paradas, de derecha a izquierda) y cómo terminamos el ascenso (abajo, a la izquierda). La distancia al M-Value (algoritmo Buhlmann) es el margen de seguridad (configurable con los GFs Low y High) en ambos casos.
Actualización a 02/12/2025: Toy flipando.
Y ésto?!?
https://viviendoapesardelacrisis.blogspot.com/2023/05/shearwater-teric-swift-smart-ai.html
Tampoco veo desde cuando.
Actualización a 03/12/2025: Va:https://cdn.shopify.com/s/files/1/0838/3732/1530/files/Teric-Tern-Release-Notes-v36-English_3.pdf
Actualizado.
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