Oceanic Geo 4.0 review

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@outofofficebrb Oceanic specs show 24 dives stored in log, but I haven't surpassed that mark on this unit to verify yet. As for MacDive, I'm hesitant to buy the app for fear that I may find I have the same issue. Will have to ponder that.

Subsurface is free. It runs on Windows, Mac, and Linux. It has companion apps for Android and iOS. All free.

And it has free Cloud storage, so your log will never get lost and can be automatically synchronized between all your computers and mobile devices.

Subsurface supports just about every dive computer there is. You can download via Bluetooth from your dive computer to the mobile app on your phone or via Bluetooth (or cable, if you have an older dive computer) directly into your laptop or desktop computer. It's nice because you can continue using the same software, with just one dive log, even if you get a different brand of computer some day. And if you dive with 2 computers and download them both, Subsurface will automatically merge the dives, so you only see 1 dive in your log, even though you downloaded it from 2 different computers. You can toggle back and forth in Subsurface to display the dive profile from whichever computer you want.

My Subsurface log has all my dives from ever. It is combined from downloads from at least 7 or 8 different computers I have or have had.

Subsurface also has a really nice dive planning tool built into it.

Subsurface | An open source divelog

It's free! Nothing really to lose...
 
If you don't want DSAT you can also look at the Aqualung i200c which is similar for $370
 
I wanted to provide an update on my review of the Geo 4.0 after having used it for about 40 dives.

Screen Navigation:
While the screen navigation is a bit confusing at first, once you get used to it, it starts to make sense and is no longer an issue.

Bluetooth connectivity:
After connecting the Geo 4.0 to several other devices without issue, I must conclude that the connectivity issues I was experiencing are unique to the phone I was using (iPhone 7). Unfortunately I have not tried connecting to another iPhone 7, so I can't say if the problems are specific to my own phone or a general problem of bluetooth connectivity with the model. Either way, it seems the Geo 4.0 is not the issue.

Gas Switching:
Researching a bit, I found that the Geo 4.0 has the capability to switch gasses during the dive. So you could for example set your primary/back gas to 30% EAN, and set up a seperate deco gas like 50% EAN, then switch between them during your dive. I'll be testing this out on some easy dives over the weekend and report back on ease of use/intuitiveness of this feature after I've had some time to play with it.
 
Gas Switching:
Researching a bit, I found that the Geo 4.0 has the capability to switch gasses during the dive. So you could for example set your primary/back gas to 30% EAN, and set up a seperate deco gas like 50% EAN, then switch between them during your dive. I'll be testing this out on some easy dives over the weekend and report back on ease of use/intuitiveness of this feature after I've had some time to play with it.

My first computer, an Oceanic Atom 3.0 had the feature as well. One of the most useless features ever, in my opinion.

If I'm doing a recreational dive, I'm not going to be doing a gas switch to a deco gas.

If I'm doing a technical dive, carrying one or more deco gases, then I am going to be using a technically-oriented computer - not an Atom or a Geo.

Anyone using a Geo (or Atom) to track their inert gas tissue loading, where they are switching to a different gas during the dive (an actual different mix, not just to a different cylinder of the same gas), is, well, to be polite, diving with way more risk than I would be remotely comfortable with.
 
...Anyone using a Geo (or Atom) to track their inert gas tissue loading, where they are switching to a different gas during the dive (an actual different mix, not just to a different cylinder of the same gas), is, well, to be polite, diving with way more risk than I would be remotely comfortable with.

@stuartv This is interesting, could you elaborate on why you feel the risk is too high? The optional Pelagic Z+ setting is a Buhlmann based algorith, which tech divers seem to prefer. Is the problem that we can't know the exact conservatism factor since it's a proprietary algorithm?

I have no tech training at this point, so just curious to understand the thought process.
 
Cycling through screens is not intuitive until you get used to the quirks. From main screen, the bottom left button cycles you through secondary screens. Then you press the upper right button to select a secondary screen. So far, so good. Now here’s where it gets stupid – at this point, the upper right button cycles options, while the lower left one changes the setting.

Best resource for getting familiar with screen navigation and settings is the U-Tube video about the Geo 2.0 – the screens and functionality are nearly identical.

Thanks for the review.

It's a shame that they didn't upgrade the UI much from the Geo2. That, IMO is the Geo2's biggest drawback.
 
@stuartv This is interesting, could you elaborate on why you feel the risk is too high? The optional Pelagic Z+ setting is a Buhlmann based algorith, which tech divers seem to prefer. Is the problem that we can't know the exact conservatism factor since it's a proprietary algorithm?

I have no tech training at this point, so just curious to understand the thought process.

When a computer manufacturer says their algorithm is "based on Buhlmann", that is like saying Dale Jr's "stock car" (NASCAR) is based on a Chevy Monte Carlo (or whatever he drives (drove?)). What is really on the inside might have VERY little to do with the car it is "based on".

Even though PZ+ is "based on Buhlmann", the actual implementation of PZ+ is still proprietary. Which means the only ones who can say what the algorithm will do in any particular circumstances (e.g. you're ascending at the end of a dive and switch from Air to pure Oxygen) are some people within Oceanic, and whatever software they put out as a dive planner. And there is no guarantee that what it does in one scenario will be similar and predictable in a slightly different scenario. E.g. if you overstay your NDL by 1 minute and it assigns you 1 minute of deco at 10', does that mean that you can comfortably predict that if you overstay by 2 minutes, it will assign you 2 minutes of deco, or somewhat close to it? No. We don't know. For all we know, overstaying by 1 minute might give 1 minute of deco, but overstaying by 2 minutes might give you 10 minutes of deco.

Saying "we can't know the exact conservatism" is a statement that actually implies we know far more than we really do.

For technical diving, we require a way to plan our dives in advance, so that we know what our ascent should be. I.e. how long we can stay down, how long we have to stop at each depth on the way up, what gases we're going to use, when we're going to switch to each gas, and how much of each gas we expect to need.

If we're going to use out computer to track gas switches and tell us how long we really need to stay at each depth during the ascent (versus following a pre-written plan and only using the dive computer to track depth and time), then we need the dive computer algorithm to exactly match the algorithm in the planning software we used.

You could possibly do that with software from Oceanic. I don't know. Meaning, if Oceanic has dive planning software that purports to match the PZ+ algorithm, I still don't know if it allows you to plan a decompression dive, and I don't know if it allows you to make a plan that includes gas switches, and I don't know if it does anything to calculate gas volume requirements (though you COULD do that part by hand or in other software, once you know what the actual ascent is).

But, even if it does all that, technical divers are generally mistrustful of anything that is not tried-and-true, as well as anything that can't be independently verified. The actual Buhlmann with Gradient Factors algorithm is very much "tried-and-true" and it is not proprietary, so there are a variety of ways to plan a dive using that algorithm and then independently verify that your plan is valid. For example, you could do the same plan in Subsurface and in Multi-Deco and verify that you get the same results. There is no way to do that with the Oceanic, since the algorithm is proprietary.

My final thought is that one might think, "well, I'm not going to do a tech dive. I'm just going to do an NDL dive. But, I went to switch to a richer gas at the end, in order to off-gas more quickly or more thoroughly. So, I don't need to do all that extensive, formal planning, like you would do for a technical dive." That is a valid point. But, even if you were doing that, I personally would only be comfortable with taking that approach using a computer with a non-proprietary algorithm. The reason is this:

Let's say you do an NDL dive on air. You ascend to 20' and switch to pure Oxygen. You do a gas switch on your Geo to tell it you're now breathing pure O2. You hang for your 5 minute safety stop while you breathe O2. You finish your dive and get out. You do a 1 hour surface interval and want to get back in.

At that point, your computer has some internal "memory", or model, of how much inert gas is still in your tissues. What it thinks about your status, based on your last dive, is going to affect the NDL it gives you for the next dive. And there is the rub. Being proprietary and unpredictable, I personally would not have high confidence that what it thinks is safe for the next dive is really safe. I mean, it probably is. But, it's almost the opposite of tried-and-true. There is no significant community of divers that have been using that algorithm to do that type of diving (that I know of, anyway), so, there is no big pool of historical data to look at and inform us that diving that way is reasonably safe. In contrast, we are pretty well informed that you could do that kind of diving using, for example, a Shearwater computer, and have some confidence in your own safety.

I hope that helps. Feel free to fire away if you have more questions. :)
 
I'm sure PZ+ is just fine for recreational no-stop diving, I'm just not quite sure why one would bother dragging multiple gases on an open water no-stop dive. I think if your dive involves gas switching, it should be a planned technical dive, in which case see Stuart's explanation.
 
My first computer, an Oceanic Atom 3.0 had the feature as well. One of the most useless features ever, in my opinion.

If I'm doing a recreational dive, I'm not going to be doing a gas switch to a deco gas.

If I'm doing a technical dive, carrying one or more deco gases, then I am going to be using a technically-oriented computer - not an Atom or a Geo.

Anyone using a Geo (or Atom) to track their inert gas tissue loading, where they are switching to a different gas during the dive (an actual different mix, not just to a different cylinder of the same gas), is, well, to be polite, diving with way more risk than I would be remotely comfortable with.
Having a multi gas capable computer is helpful for people starting to do accelerated deco. It doesn’t need to cost a fortune and exactly match some theoretical plan. They can have a plan on a slate and follow the more conservative of the slate and the computer. Being beginners they would not be doing 60 minutes at 60m and the biggest difference will likely be how long the last stop is. Think of it as a slightly opinionated bottom timer.

Expecting people to buy a £700 computer just to do a bit of accelerated deco is a bit unnecessary.
 
Having a multi gas capable computer is helpful for people starting to do accelerated deco. It doesn’t need to cost a fortune and exactly match some theoretical plan. They can have a plan on a slate and follow the more conservative of the slate and the computer.

[snip]

Expecting people to buy a £700 computer just to do a bit of accelerated deco is a bit unnecessary.

And there is the rub, isn't it? What if the computer is more conservative and says to hang for 30 minutes?

I have no problem with doing multi-gas diving and using a computer like the Geo in Gauge mode. I just would not personally use the multi-gas feature of a Geo to inform my ascent.

So, who EXPECTS people to buy a 700 pound computer? (said or implied)
 

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