Gradient Factors - What is Everyone Using?

[NAM001]

Could you show that chart? I suspect it is for the first dive only?

this is an example of what the chart loks like. under settings it starts with a r or a t for rec vs tech mode on the computer. teh GFhi is the GF that that setting for that maker for that mode mimics.

 

[NAM001]

Could you show that chart? I suspect it is for the first dive only?

here is another chart that is available somewhere. it is not as easily read because some of the settings are not shown onder the lissting in the first column

 

[scubadada]

Hi @KWS

All the computers in your two charts run Buhlmann ZH-L16C or B with presets with designated GFs. For simplicity, if you are doing no stop dives, it would be easy to choose GF highs that are identical, or very close, so that your NDLs would be quite similar. One would think that they would stay pretty close for repetitive dives. With the exception of Shearwater, you are unlikely to see the others while diving. The Liquivision Lynx and the Dive Rite Nitek Q are gone. I still have a perfect Nitek Q I bought for $400 from DGX in 2016, but I dive a Teric now. I rarely have seen a Ratio in the US and have never seen a Mares Genius.

For some reason, I thought your chart was going to show a variety of commonly seen computers running deco algorithms other than Buhlmann, like DSAT, PZ+, and flavors of RGBM. After diving DSAT and Buhlmann together for a little over 4 years and about 800 dives, I can safely say that the two algorithms cannot be matched over a series of dives. DSAT starts off relatively more liberal, especially if deeper, and would require a GF high of 99 for a close match. On repetitive dives, especially if shallower, Buhlmann becomes more liberal and would require a reduction in the GF high to 90 or even 85, to match DSAT. It drove me crazy changing GFs, so now I just leave it on 95 and dive the more conservative of the 2, or do a little deco.

I have a rough idea of how one could match PZ+ with Buhlmann, but have no idea how to match any other common deco algorithm, fortunately, I don't have to

Your 2nd chart came off SB might have been @Jay

 

[EFX]

Just as a point of reference I ran 5 dives with different GF's using my spreadsheet. All the dives were on air at 80 ft for 20 minutes using Buhlmann ZHL-16C. No safety stop, no additional gases, 60 fpm descent rate, 30 fpm ascent rate. Here are the numbers in order GFLo, GFHi, NDL time, Deco time (NDL is at 80 ft for 20 min BT which includes the descent time, deco time is total for the dive and includes the ascent time):

60, 60, 0, 6.7
60, 70, 0, 3.7
60, 80, 0, 3.7
60, 90, 2, 0
60, 100, 7, 0

I replaced the GFLo to equal the GFHi and got the same numbers above.

 

[scubadada]

Just as a point of reference I ran 5 dives with different GF's using my spreadsheet. All the dives were on air at 80 ft for 20 minutes using Buhlmann ZHL-16C. No safety stop, no additional gases, 60 fpm descent rate, 30 fpm ascent rate. Here are the numbers in order GFLo, GFHi, NDL time, Deco time (NDL is at 80 ft for 20 min BT which includes the descent time, deco time is total for the dive and includes the ascent time):

60, 60, 0, 6.7
60, 70, 0, 3.7
60, 80, 0, 3.7
60, 90, 2, 0
60, 100, 7, 0

I replaced the GFLo to equal the GFHi and got the same numbers above.

Hi @EFX

Interesting post. My Oceanic VT3 running DSAT has a 1st dive NDL of around a GF high of 99, the NDL is 30 min, +10 on your dive. If it was running PZ+, a GF of around 90, the NDL would be 26 min, +6 on your dive. The descents may not be counted. My Teric says it has an NDL of 29 min at 99, 24 min at 90, and 19 min at 80, the only dive requiring a short deco stop. Your sims are interesting. I look forward to running them on MultiDeco when I get my computer back from repair

 

[NAM001]

Hi @KWS

All the computers in your two charts run Buhlmann ZH-L16C or B with presets with designated GFs. For simplicity, if you are doing no stop dives, it would be easy to choose GF highs that are identical, or very close, so that your NDLs would be quite similar. One would think that they would stay pretty close for repetitive dives. With the exception of Shearwater, you are unlikely to see the others while diving. The Liquivision Lynx and the Dive Rite Nitek Q are gone. I still have a perfect Nitek Q I bought for $400 from DGX in 2016, but I dive a Teric now. I rarely have seen a Ratio in the US and have never seen a Mares Genius.

For some reason, I thought your chart was going to show a variety of commonly seen computers running deco algorithms other than Buhlmann, like DSAT, PZ+, and flavors of RGBM. After diving DSAT and Buhlmann together for a little over 4 years and about 800 dives, I can safely say that the two algorithms cannot be matched over a series of dives. DSAT starts off relatively more liberal, especially if deeper, and would require a GF high of 99 for a close match. On repetitive dives, especially if shallower, Buhlmann becomes more liberal and would require a reduction in the GF high to 90 or even 85, to match DSAT. It drove me crazy changing GFs, so now I just leave it on 95 and dive the more conservative of the 2, or do a little deco.

I have a rough idea of how one could match PZ+ with Buhlmann, but have no idea how to match any other common deco algorithm, fortunately, I don't have to

Your 2nd chart came off SB might have been @Jay

sorry about that there are other charts out there that use other than buhlman where the GF hi is a value that is the equivilant GF to say a med setting in a rgbm COMPUTER. i only had these 2 readily available but others are out there on the net.

Its very possible its source was him. I have one some where where it was a cresi or something that did not use buhlman and it had equivilant GFs associated with the setting for comparison purposes. there is no tell in how each programmer is using them but the charts are an attempt to relate the end results. You could probebly take your non buhlman computer select low conservatism and then look at teh dive plan to see what the ndl is. do that with lo med hi or 0 1 2 3 settings. after a while you can make such a table which I suspect really shows conservatism setting s vs NDL value. when you do that with a buhlman computer note the default GFs assigned and match teh NDLs in groups,,,,,, a 20 min ndl may be a gf95 a 18 min ndl may be gf 90 etc. Nothing is going to be absulutely accurate but any computer that can provode an ndl can be figured out. And you are right We can match up our conservatism settings to get all on the same NDL time table. if you loose one of hte divers you know everyone should hit the surface with in a 2 minute window past that you ahve a potential missing diver.

 

[scubadada]

Hi @KWS

All the proprietary deco algorithms deal with repetitive dives differently. Even if you had a clean 1st dive match for GFs, it would not hold up for subsequent dives. My example for DSAT is a case in point.

 

[EFX]

Hi @EFX

Interesting post. My Oceanic VT3 running DSAT has a 1st dive NDL of around a GF high of 99, the NDL is 30 min, +10 on your dive. If it was running PZ+, a GF of around 90, the NDL would be 26 min, +6 on your dive. The descents may not be counted. My Teric says it has an NDL of 29 min at 99, 24 min at 90, and 19 min at 80, the only dive requiring a short deco stop. Your sims are interesting. I look forward to running them on MultiDeco when I get my computer back from repair

Hi @scubadada ,

The NDL you report is at arrival at 80 ft. The NDL in my post is at the end of the BT at 80 ft. To make the comparison equal your GF of 99 would show just +3 over my dive. Your GF of 90 would be +4 over my dive. Your Teric at GF 99 would be just +2 over my dive.

 

[tursiops]

The NDL in my post is at the end of the BT at 80 ft.

Not a very helpful definition! NDL in a planning mode usually means how much bottom time do I get.

 

[EFX]

Not a very helpful definition! NDL in a planning mode usually means how much bottom time do I get.

Good point. For the same dives in salt water I get 22 min for a GFHi of 90, 27 min for a GFHi of 99. In fresh water I get 24 and 29 minutes respectively.