 |
Introduction
I must admit that I am an old-fashioned guy when it comes to decompression.
I still carry deco-tables with me on every dive. Not that I have anything
against the dive computers - I have and use two – but until recently,
there were no computers that could effectively provide deco information for
trimix diving. Any computer can malfunction and will cost more than a set
of tables, so if the tables happen to float away or fall overboard, I just
reach into my dive bag and pull out another set and go diving. Additionally,
since I mostly dive the same profiles (caves, wrecks) many times over with
the same sets of gases, I can tweak deco profiles to give me the most favorable
off-gas/time-in-the-water solution. The various deco software packages incorporated
the notion of deep stops for years, while dive computers are just starting
to take advantage of optimized deep stop profiles. I like deep stops as they
make me feel better after the dive.
For years I was using the Z-plan, created
by the late Will Smithers, to generate my deco tables. The
Z-plan incorporated so called Pyle deep stops, named after
Richard Pyle, who empirically determined deep stop strategy
based on his fish collection techniques. Z-plan’s Buhlmann-based
algorithm is becoming little dated with respect to the new
Deep Stop theories based on the RBGM and VPM bubble models,
so I was ready for a new deco software. My requirements were
simple: the software needs to cover all types of diving I do – Nitrox,
Trimix, open (OC) and closed circuit (CC). It should incorporate
deep stops, since I personally use them and feel better after
dives with deep stops and slow ascents. The last requirement
was, that the software should be able to easily generate preformatted
tables, because I grew tired of rewriting my tables on the
slate or wet-notes (I love the portable laminator).
With that information in hand I started searching
for my next deco-planning software. There are essentially three
different “flavors” of decompression algorithms
that incorporate deep stops: Bühlmann with Gradient Factors,
VPM, and RBGM (see sidebar). I have found representative deco
packages from each algorithm category and decided to run them
through a little test to determine the most suitable deco software
for me. The candidates are Z-planner, V-planner, ProPlanner,
DecoPlanner, and GAP. I added Palm based Dplan and Decoweenie+
to the mix as I often use my Palm Pilot to tweak deco profiles
at the site.
The Participants
 The Z-planner is
a very cool “skin” – graphical user interface – created
by Ross Hemingway for the DOS based Z-plan. The Z-planner has
a simple, but clever data entry screen, where user can enter
Depth, Time, and Gas Mix for each level of the dive plan. Each
entry is saved and can be used in the next planning session.
The deco gases are entered in similar fashion, but cannot contain
Helium, only Oxygen and Nitrogen. In Closed Circuit mode the
set point and Scamahorn slide value are entered. The configuration
screen holds standard deco parameters – feet/meters,
salt/fresh water, descent/ascent rates – as well as conservatism
and an option to use Pyle or WKPP deep stops. The deco profile
generated by Z-planner is the actual text output from the Z-plan
executable. The Z-planner is simple to use and very user friendly,
but the lack of He in deco mixes and plain text output are
slight drawbacks.
 Decoplanner (v.
3), developed by Simon Tranmer, is a mainstay deco planning
software of Global Underwater Explorers training agency. I
had an opportunity to review the latest version, still in beta,
which includes number of new features. The most notable is
an inclusion of the VPM algorithm in addition to the Bühlmann
model with Gradient Factors. The deco profiles can be calculated
side by side using each algorithm and compared to determine
best deco strategy for the given mission. The beta version
of Decoplanner I had available used a VPM-A algorithm, which
is rather aggressive in treatment of shallower stops. The final
version of the software will use the VPM-B, currently accepted
as a safe implementation of the VPM algorithm. The Decoplanner
has a very clean “spreadsheet-like” interface providing
divers with all necessary information right on the screen.
User can change any parameter of the dive and recalculate the
profile with a click of a button.
Bailout tables accounting for loss of all deco gases are generated in the same
manner. The software easily accommodates multi level (up to 19 levels), multi
dive and multi day missions as well as up to 10 decompression gas mixtures.
Calculated deco profiles include both stop times and run times for each deco
level as well as gas requirements, Gradient factors, M-values, CNS and OTU
information. All 16 compartments can be analyzed for each segment of a dive.
The information in the analysis window includes partial pressures of all inert
gases, M-values, % M-value, gradient factors, and % ambient pressure. The dive
can also be analyzed on a set of graphs displaying multitude of parameters.
The table generation engine will create preformatted set of tables for a range
of depths and times greatly simplifying dive preparation. The Decoplanner can
be preconfigured with custom deco gas set combinations covering every imaginable
dive scenario. All standard dive parameters can be customized in dive preferences.
The software does not have capability to calculate constant PPO2 deco
profiles making it unsuitable for closed circuit
rebreather (CCR) dive planning.
|
|
Pro-Dive Planner (v. 7.12C), created by Nick Bushell and
Kevin Gurr, is the only software package with the DOS interface.
It requires sequential data entry and edits are little more difficult
than in its Windows and Palm counterparts. The software uses a proprietary
algorithm to add micro-bubble controlling deep stops to the derivative
of Bühlmann ZLH-16a algorithm. Pro-Dive Planner has a facility to
predefine different gases for sequential depth intervals and those
can then be used in planning the actual dive. Other customizable
parameters include safety factor, micro bubbles, atmospheric pressure,
breathing rate, and a last stop depth. The micro bubble adjustment
will force deep stops, although the logic and functionality of this
setting are not explained in the manual. Although the DOS interface
of the Pro-Dive Planner is little dated by current standards its
biggest advantage is that it uses the same algorithm as VR-3 dive
computer and can communicate with it. Downloaded dives can then be
used for future dive planning. A new version of Pro-Dive Planner
is on the horizon.
 V-Planner (v.
3.22), created by Ross Hemingway, uses the VPM-B algorithm which
is Erik Baker’s latest extension to the decompression model.
The V-Planner interface has its roots in the Z-Planner “skin”,
but many features were greatly enhanced here. Multiple users can
use the software and all parameters are preserved for each diver.
Bottom, travel mix and Deco gas windows hold a history of dive profiles
for each diver. To set up a new dive is as simple as clicking the
check boxes next to each depth/gas mixture and deco gas combination
and hitting a Calc button to generate the deco profile. The V-planner
can be configured to a very fine detail including the VPM model parameters.
In addition to deco profile calculations the software can calculate
bailout profiles for any combination of lost deco gases, as well
as profiles for range of depths and times. CCR and SCR dive plans
are also supported. Air breaks can be inserted and accounted for
in the deco profile. The V-Planner is a very powerful and streamlined
implementation of the VPM deco model; the only drawback is a lack
of preformatted table generation. The profiles are output in plain
text, in abbreviated run time format, and also in the CSV data format
to allow for further use in Excel or elsewhere.
 GAP (v.
2.1) – Gas Absorption Program created by Kees Hofwegen and
Peter Fjelsten, is on the edge of deco modeling envelope. It offers
both, Bühlmann with Gradient Factors (Bühlmann GF) and RBGM (Reduced
Gradient Bubble Model) algorithms in a well packaged graphical user
interface (GUI). The GUI is extremely user friendly with all pertinent
information available in dockable panels. In the center stage is
a deco profile window showing both, Bühlmann GF and RBGM profiles
side-by-side for comparison. The deco tables can be generated with
a single click of the mouse for either of the two algorithms. GAP
has by far the best table generation engine that I have seen in a
deco software. Tables can be generated in HTML, CSV (text for import
to Excel), and direct printout. The well laid-out configuration panels
make setup of default parameters a snap. All standard configuration
options are available as well as the ones pertinent to the RBGM model.
GAP uses a template metaphor to store multitude of configuration
data. Bottom and deco gases are also stored in the template. I use
different templates for cave and wreck diving as well as for closed
and open circuit dives. Each profile can be switched between OC and
CC system with a click of a button giving user a chance to evaluate
which system is more suitable for the dive.
All aspects of GAP are accessible from a toolbar above a workspace.
Entire interface is very well thought out. A spreadsheet-like grid
facilitates the data entry while the profile is displayed graphically
at the same time. The dive profile waypoints can also be drawn directly
into the profile window and the data entry grid gets updated automatically.
Deco gas, deco model/algorithm, tissue loading, and dive info panes
can either “fly-in” on mouse-over, or can be “pinned” to
the sides of the main workspace. Very slick!
Extensive bailout table generation engine is another forte of this
package. The bailout can be calculated for a loss of any and/or all
deco gases used in the dive. The bailout tables include the gas usage
calculations to help in planning for the emergencies. Managing/planning
multidive days and multiday diving is easy with GAP. Profiles can
be saved and retrieved and the associated template is always attached
to the profile set. Overall, the GAP is very user-friendly application
having a smorgasbord of capabilities supporting the latest developments
in the decompression theory and modeling.
Decoweenie+ (v. 1.5), created by Phi Le, is a very sophisticated
deco program for the Palm OS. The sheer volume of features can be
overwhelming for the uninitiated, but the expert will be hard pressed
to find a feature that is NOT available in the DW+. The deco profile
can be calculated using a variety of options; from straight Bühlmann,
to Pyle, GWE, and Gradient Factors, as well as DCAP algorithm by
Bill Hamilton. The VPM and possibly RBGM modes are planned in near
future. DW+ can calculate plan for any combination of open circuit
(OC) and closed circuit (CC) diving, has color graphical user interface,
and a very simple data entry grid for dives with up to three depth
levels. More complex dives are handled through the WayPoint Wizard,
a spreadsheet-like grid that allows for fine control of every depth
level. The WP Wizard can handle very complex profiles and has a time
saving “return” feature for cave profiles where trip
back is an exact mirror of the trip there. Decoweenie+ can maximize
the “O2 window” deco stop and has an option
for the user to “shape” the deco profile manually and
compare it to the straight Bühlmann generated profile. The bottom
and deco gases can be selected from user defined sets or calculated
from MOD/END and best Mix parameters, entered manually, or auto-selected
from GUE standard gases. DW+ can calculate a range of depth/time
tables, as well as OC bailout for a CC dive. It comes with a Gas
mixing application that includes a real gas (Z-factor) option for
preparing dive gases. The Decoweenie+ is one of the most rounded
deco modeling applications that I have come across, and the fact
that it fits in my pocket (on a PalmPilot) is an added bonus. It
can easily compete with its desktop counterparts with one exception,
the table output is text based so it requires formatting or transcription
before it can be effectively used for diving.
Dplan (v. 1.1 ), created by Todd Leonard , is a Palm OS based
deco software. It is brought to you by GUE and follows the same time-honored
design highlights of its PC brother – Decoplanner. Dplan sports
no-nonsense grid data entry screen with drop down selection of depths,
times and pre-defined bottom gases. Any of the parameters can also
be entered in place using the Grafitti pad. The deco gases are also
selected from the customizable predefined list. After that it takes
just a push of a button and the dive plan scrolls on the screen.
The Dplan uses the Bühlmann GF algorithm to calculate decompression.
The dive preferences, including gradient factors, are set and stored
during the initial configuration and can be changed at any time before
another dive mission is planned. The dive profiles or multiple dive
missions can be stored in named files and retrieved for additional planning/modification.
The dive profile is limited to 7 waypoints and mission can have maximum
of 8 dives. Although the Dplan can not plan closed circuit dives,
it is extremely easy to use and provides efficient decoprofile generation
engine for the Palm based devices. If the Decoweenie+ is a Leatherman
of Palm deco software then Dplan is a butcher knife cutting right
to the bone of its intended purpose.
The Test 
I have run the same dive profile through each of the reviewed packages,
to help me with a selection of my next deco software. The profile
is a 270 feet deep dive for 30 minutes. It is a dive I have done
numerous times, so I know what an acceptable deco profile should
look like. I have set preferences in all deco packages to the same
values, including 0 conservatism and let’em rip. The results
are in Table 1. Please note that the profiles were generated with
settings that are not the same as yours. Do not use these profiles
for diving; they are intended for comparison only. The results show
that there is not much variability among different deco packages,
only in starting depth and frequency of the deep stops. The deep
stop shape of the profile is a very individual topic as everyone
responds differently to the deep stop decompression.
The Curve Ball
All reviewed software performed as expected calculating the decompression
profiles, it mainly differed in the ease of use and breadth of features.
This is to be expected, since all packages are well-researched decompression
models. It was time to explore some boundary conditions of the model
implementation. I dive this peculiar cave profile, which forces me
to ascent from 160 to 3 feet in the middle of the dive before descending
back to 70 feet for additional 20 minutes. So, I threw this profile
at all of the packages. Each software handled this curve ball differently,
but only V-Planner and Decoweenie+ have actually intercepted the
dive profile, calculated the necessary deco, and then continued with
the dive. Decoplanner and Dplan aborted the dive with a warning of
exceeded deco ceiling, while Pro-Dive Plan would not let me enter
a depth above the profile ceiling (there are some advantages to sequential
data entry). GAP and Z-planner just continued with the profile without
any warnings about a blown deco ceiling!
Some might argue, that profiles like these are not safe, but that
is not the point. In this exercise I am testing software for my personal
use, and I personally want to be able to plan profiles like this.
Conclusions 
All of the deco packages presented here are very fine products and
would serve me well. But one must keep in mind that even the best
deco planning software is just an imperfect approximation model of poorly
understood processes involved in decompression. The Bühlmann based
models have the advantage of being the oldest, thus tested by greatest
number of divers. That does not necessarily make them safer, as the
research and evidence of the last decade shows that gas phase models
like VPM and RBGM are very valid approximations of the decompression
process. Additionally, each of us responds differently to hyperbaric
conditions, so what works for one does not necessarily have to work
for someone else.
I still cannot decide what deco package to use in my future diving.
They are all very good. What do you think? Share your opinions and
recommendations at ADM discussion forum (www.advanceddivermagazine.com/Forum/default.asp).
But enough theory, lets go diving! |
|
)
)
)
)
){kind=small}
)
Home | Members| ADM Store | Forum | Photo | Expeditions