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I sent this to out DIR UK list and it was suggested that a personal
perspective on GUE's decoplan may be of interest to the wider group...

Firstly, I like to cut tables and laminate them so that they are reusable.
Since they are re-usable, I decided to spend a reasonable amount of time
deciding on the format.  This format has changed over the years and I found
it annoying to have to go back and adjust all the old spreadsheets (that
contained my profiles) to any new format.  Accordingly, I developed a
spreadsheet with database lookup functions to select the appropriate deco
data and load it into a single sheet.  Amongst other benefits, this allows
the format to be adjusted in the one sheet if I every want to again.

I looked at Proplanner but this used to be so tedious and time consuming that
it took for about 4 hours to cut a complete set of tables for a gas with
time, depth and contingency options.  (I cut a wide variety of tables so that
if we have to change the dive site to something different, then I have the
tables for this depth also.  I prefer not to cut tables on the boat.  For
example, if I have an 80m gas, I'll have tables for 40m, 45m, 50m, ..., 80m,
together with run times and gas failure options.)

I then invested three or four times the price of decoplan in Abyss and
despite many of the annoying bugs I have been reasonably happy with it.  The
reason I liked the Abyss is that table generation is very easy and it reduced
my time to cut tables down to about 2 hours.  I then started doing dives
where three or more deco gasses were used and found that doing bailouts was
not really a viable option.  The Abyss then took me about 1 hour to cut
tables as deco gas failures were then planned using a rule of thumb.

When I was introduced to decoplan towards then end of 1999, it was a breath
of fresh air (should this be a breath for fresh Trimix) in its ease of use.
I can now cut a set of tables that would have taken hours in about 10
minutes.  Obviously, the use of Gradient Factors is a major step forward in
allowing the diver to control the safety within the entire profile, rather
than some arbitrary %age safety factor.

I would have liked to add some comments about the profiles and the validity
of them, but as I have *personally* only done a handful of dives, *my*
experience is not statistically significant.  As the software has been in use
in the UK for 2 years, others may want to comment further.  The dives I have
done are three 60-65m dives for 30 minutes ABT with GFLo 20, GFHi 100, with
some shaving of the O2 stop over and above the GFHi setting, and a 80m dive
but had to improvise as it was too cold to stay down for long and got out on
the fastest table I carried.  I've also done a few short 35m dives with
minimal deco.  However, it was reassuring to see the deep stops coming in at
12-15m.  I made a comparison of decoplan with the above GFs and a 108m dive I
did in South Africa.  The profile was almost identical with the same stops
from 69m right up to the 12m stop, after which decoplan with these GFs got me
out considerably quicker.  (The 108m dive had been planned with the Abyss,
and deep stops added based on guesswork which was seemingly spot on.)

I though about adding some comments about the other functions of decoplan.
However, when I though about it, I realised that what is needed in deco
software is just as in diving: a no-frills, fit for purpose, simple but
effective piece of software that gets the job done.  The more that I learn
about deco and diving, the more convinced I am that this is true.  Ease of
cutting a range of tables and GFs are the hot buttons for me. Certainly, it
has been money well spent.

David Shimell
Email: shimell@se*.co* <mailto:shimell@se*.co*> 
Project Manager, IBM NUMA-Q, Sequent Computer Systems Limited,
Weybridge Business Park, Addlestone Road, Weybridge, Surrey, KT15 2UF, UK
registered in England and Wales under company number: 1999363, registered
office as above

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