DecoPlanner

In1994, UK native Simon Tranmer, the original author of DecoPlanner, began his diving career with a PADI Open Water course in the Maldives. Back in the UK he continued his training with more PADI courses and ended up with a Master Scuba Diver rating by July 1995. He then joined a branch of the British Sub-Aqua Club (BSAC), where he met Graeme and Sue Davison, Andy Kerslake, and Keith Bellamy. They all went on to train with Jarrod Jablonski.

– In 1997, I did a trip with the group from the club to Scapa Flow where I did a TDI Advanced Nitrox Diver course taught by Graeme and a TDI Staged Deco course with Keith Bellamy. Back in our accommodations in the evenings, we all discussed decompression theory—obviously, as it was the main focus of the courses. They were all bemoaning the fact that managing decompression, especially on multi-level dives, was very difficult and that it would be great if someone could come up with an easier way. As a professional computer programmer with a lot of experience, and probably some misplaced optimism, I suggested that I could write a program to do these kinds of calculations, remembers Simon. And so, it began.

– I started to assemble the program, and the guys from the club put me in touch with Erik C. Baker (the American engineer who introduced the gradient factor concept). He supplied me with a ton of information about the research he had been doing. Once I had the program in a state where we could generate some profiles and had incorporated some of the information from Erik about gradient factors, we started using it and comparing it with profiles generated from other sources. It seemed to produce what we thought were good results. I shared the program with Graeme, Sue, Andy, and Keith and they started testing it too. My own diving got more technical, and my buddy Paul Brown and I started using the program for all our dives.

– Paul, Andreas, and I went on to train with GUE—passing Cave 1 in 2002 with Tamara Kendel—and Paul and I did Cave 2 in 2004 with David Rhea, Simon ends.

Simon retired from diving in 2013 at the age of 60 after the development of a knee problem that made frog kicks painful.

Enter Andreas Hagberg

GUE founders and instructors were using the DecoPlanner software from the organization’s inception in 1998, and the source code was passed on to GUE around 2000. At this point in time, version 2.0 was in use. The development slowly progressed towards a version 3.0 with the help of other British coders who wished to remain anonymous.

In the early 2000s, I had earned a university degree in software engineering in Sweden, and in my spare time I developed a small multi-platform program for helping with nitrox and trimix gas filling and related calculations (Gas Management Program), as well as a very simple dive help finishing up the development of DecoPlanner towards a 3.x release, which I happily did. log program. As these programs were aimed towards GUE divers, Jarrod Jablonski became interested in distributing them through GUE.

In 2005, Jarrod asked if I could help with finishing up the development of DecoPlanner towards a 3.x release, which I happily did. The following year brought me to Florida and a full-time position at GUE as webmaster and programmer.

Complete rewrite

A few subsequent versions were developed and released on the original code base, which was Visual Basic. As Microsoft reduced their support for this development platform, it became apparent that migrating the code to a newer standard would be a considerable undertaking. We had some options. Did we want to stay on a development platform where some of the old code could potentially be re-used, or migrate to a different coding language that could work on multiple different end-user platforms?

As most GUE instructors were using Mac computers, we decided on the latter. About a decade earlier, I had already translated some of Erik Baker’s Fortran code to Java, which I used in a tool that analyzed the gas loading from real dive profiles downloaded from the old Sensus Pro dive loggers. Because of this, deciding to rewrite DecoPlanner from scratch in Java (JavaFX, specifically) felt a bit more sensible compared to starting from nothing.

Familiar layout

For many years, Mac users had been using different kinds of Windows emulators or parallel environments to run the Windows-native DecoPlanner on their Mac computers. Around 2021, the most popular Windows emulator tools became incompatible with the latest releases of macOS, and the need for a macOS-native version of DecoPlanner felt more pressing.

The new rewrite of DecoPlanner was released as version 4.0 in October of 2021. As the straightforward user interface has always been one of the distinguishing and much appreciated features of the software, the same tables-based data input sections were recreated in version 4, although using a more modern look and feel. To some users, this felt outdated and “old,” while others were relieved to see the familiar layout.

DecoPlanner and ratio deco

An interesting chapter of decompression planning and GUE has been the concept of ratio deco. Although a bit late in the game, DecoPlanner 4 now includes a section aimed at those who use this method. The term ratio deco spread outside of GUE classes, but it seems the term was not well understood early on, and different interpretations unfortunately gave the term a life of its own. With its inclusion in DecoPlanner, my hope is that more people will find it easier to understand the concept.

Since GUE first started using the principle, it has been adopted by copying agencies and groups to mean something different than how GUE first used it. For a number of years, it could be a frustrating exercise trying to discuss most things regarding ratio deco, as different groups have created different meanings of the term. Some divers reported that ratio deco was too aggressive for them, which immediately made it clear that we were not talking about the same thing, as the concept of ratio deco does not define any sort of conservatism.

DecoPlanner 4 now allows for constant pO2 plans to be used for planning rebreather dives.

Looking at the concept alone, a ratio deco plan could be made from any decompression plan created from any decompression model and any conservatism setting there may be. However, many chose to focus on what was often taught as a good starting point in GUE’s tech classes, which was originally based on the first model available in DecoPlanner: Bühlmann ZH-L16b with gradient factors 30/85. To many, ratio deco represented this exact setting in DecoPlanner, followed by a rearrangement of stop times to create a linear ascent for each interval of stops for a certain decompression gas. While the standardization of this approach was useful to get larger groups of people to use roughly the same decompression profiles, it still often seemed like many people went through the GUE tech classes and still missed the full potential of the ratio deco concept.

It’s all in my head

Back when the VPM-B model was considered the latest and greatest, I personally liked to use ratio deco plans based on VPM-B. This approach was not always met with understanding. I vividly remember a dive in a deep Florida cave called Diepolder 2 when midway through our decompression, I realized that my decompression plan only existed in my head. (Bottom timers were still the GUE thing to use at the time). I didn’t even have the decompression plan in my wetnotes anymore. I was diving often and had the VPM ratios memorized well, so I was not concerned. But, as I was diving with non GUE-trained divers (all wearing fancy trimix computers), I remember never feeling completely comfortable telling them that I was diving a “ratio plan based on VPM tables” without even being able to show them that exact plan. I was concerned that a lack of understanding could take an ugly turn and restrict my access to these dives. Therefore, my official statement was often that I was diving “VPM tables,” and luckily no one asked to see those tables at the dive site.

In DecoPlanner 4, I finally decided to add a small section that would allow people to see how the original term ratio deco can be used, even though the popularity and use of the term had somewhat faded. For those that want to write down a large set of tables in their wetnotes, they now have the option to take a quick look at the ratio section in DecoPlanner and write down the approximate ratios for any decompression plan they might want to follow—be it open-circuit, closed-circuit, ZH-L16, or VPM. With the popular use of dive computers, these written plans will likely only serve as emergency plans for most. In a future version of DecoPlanner, this section of the software will likely be optional (removable), for those that see it as an unwanted distraction.

DecoPlanner Mobile

Along with DecoPlanner 4, which runs natively on Windows and macOS (for desktop/laptop), you also get the new DecoPlanner Mobile for both Android and iOS (for phones and tablets). Divers have wanted a mobile version for a long time, but it regrettably never made it to the top of my priorities. Looking back at the last decade and a half, it seems my spare time was

DecoPlanner 4 now runs natively on Windows and macOS, and is available as DecoPlanner

Mobile for both Android and iOS.

DecoPlanner

Mobile has a different user interface.

Jarrod On Decoplanner

GUE Founder Jarrod Jablonski explains his approach in working with Simon Tranmer, Graeme Davison, Sue Davison, Andy Kerslake, and Erik Baker in developing DecoPlanner.

MY PRIMARY GOALS IN WORKING WITH Erik, Simon, Graeme, Andy, Sue, et al. in the development of the program were twofold. First, I wanted to help create a very simple program that allowed divers to make changes at any point in the dive easily and quickly. I wanted to stay away from the graphical games that take a lot of time. We wanted a program that was for diving—an application where you would just punch out a profile and go. I was pretty frustrated by anything that detracts from getting a dive schedule quickly and playing with various aspects of a given dive.

Secondly, I wanted to address several seemingly mysterious parameters, like deep stops and safety factors. Erik Baker and I have spent quite some time looking over profiles and playing with schedules—everything from extended exposures in Wakulla to recreational dives on a 10 m/30 ft reef dive. I feel that “safety factors” as they are generally applied are essentially meaningless, give basically inconsistent results, and do nothing to further our knowledge of the decompression process or indeed provide a margin of actual safety. I feel similarly about deep stops that don’t use any real, dependable methodology. Our goal with the max stop depth and gradient factor use was to merge our real experience along with my work with Erik to create a logical and predictable system. I feel confident that this system offers divers the absolute best way to personalize their dives, and safety factors, as well as how to choose a sensible deep stop range.

instead spent designing and building sidemount rebreathers before they were commercially available, and of course then exploring and mapping many extra miles of cave passage that these contraptions allowed access to. Across the Atlantic in Italy, GUE diver Luca Palezza was better able to juggle his time, and he successfully developed the mobile app that is now distributed as DecoPlanner Mobile. DecoPlanner Mobile is an extremely capable dive planner with a lot of nifty features packed into the smaller screen format. While we strive to offer a similar experience between the different platforms, the desktop and mobile versions do offer a few differences in features and user interface. Over time, they will likely grow more similar.

As the decompression logic was written from a different code base and in a different language compared to the desktop version, getting the desktop and mobile versions to produce similar results took quite some time, even though they both implement the same algorithms. While a difference of a minute or two in a decompression plan feels inconsequential to most, trying to explain the difference to a new diver learning about decompression can potentially be frustrating for instructors. Which result should be trusted as the “correct” one when you are learning to follow your planned ascent down to the second?

Future updates

There are plenty of ideas for updates in line to be implemented, but selecting which ones to implement first does not always feel obvious. To one user, one missing feature might feel extremely important, while others may wish to never see that specific feature at all. To that end, we will continue to implement new features while trying to make them optional to use wherever possible.

In closing, it is recommended that you keep checking for updates, and please use the Support tab in the DecoPlanner Help section for any feedback, requests, or questions. It is a far better strategy than hoping that the developers are present on your favorite online discussion forum. 

Andreas has been working for GUE since 2006, building different iterations of the website, software packages (DecoPlanner, GMP, DiveLog), and various other technical projects. Andreas started diving in 1993 in Sweden, and after relocating to Florida he has discovered and mapped several miles of new cave passage. He also enjoys documenting those unique environments with cameras and various mapping tools, which have enabled him to contribute to several Project Baseline projects. Before starting to work at GUE, Andreas worked as a software development consultant in Sweden. He now resides in North Florida with his wife and daughter.