The Model Based Dive Computers. with Its Capability for Multi-Level And
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ORCA INDUSTRIES' DIVE COMPUTERS Paul A. Heinmiller ORCA Industries, Inc. 10Airport Way Toughkenamon, PENNSYLVANIA 19374 U.S.A. TheORCA Industries EDGE Dive Computerwas the first modelbased di ve computeravailable to recreationaldivers. After six years in thefield, andthe releaseof the SkinnyDipperas the secondin the series,over ld million divesare estimatedto havebeen made using the ORCA decompression model.Bends incidence to datehas been minimal, and less than comparable rates usingthe U.S,1Vavy tables. ORCA continues to improvehard~are andsoftw are, and plans to releasethe third computer of theseriesin 1989, ORCAIndustries was formed in 1982to develop.a revolutionary element of diving technology,the EDGE Dive Computer. The EDGE was unique because it was the first of themodel based dive computers. With its capability for multi-level and repetitive diving, theEDGE extended dive times and increased pmxiuctivity for workingdivers. Its graphic tissue-trackingdisplay has helpededucate many divers about the mathematicsof decompression.Since it implementsa ceiling depth, instead of fixedstops, for dives requiringdecompression, it allows diving flexibility which was previously unavailable. TheEDGE is a largeunit, with a fullrange of decompressionfunctions, many of whichare unnecessary for theaverage recreational diver. In 1987,ORCA added the SkinnyDipperasthe second computer in the series. Using the time-tested ORCA model, SkinnyDipperwas designed with the recreational diver in mind.It presentsan instinctive displayof information,consisting of remaining no-decompression time,depth, and dive time,and doesn't have the EDGE graphics. SkinnyDipper is smaller, lighter, and less expensivethan EDGE, and has proven to bevery popular. Although it doesn'thave the EDGE'scapability for decompression information display, it does display a ceilingdepth anddoesn't lock up or shutdown in decompressionmode. ORCAremains the leader in DiveComputers, andwill presentthe third computer in theseries at DEMA 1989. The new computer, asyet unnamed, will implementstrong pointsof bothEDGE and SkinnyDipper, andshould prove to be a verycapable machine. WARRANTY DATABASE ORCAmaintains a computerdatabase of EDGEand SkinnyDipper warranty information.Included in thedatabase are the owner's name and address, of course,but alsoinformation about the owner's diving style and frequency. Analysis of thedatabase showsthat EDGE and SkinnyDipper owners are relatively similar people, which was not expectedgiven the different marketing targets. 35 Langand Hamilton Eds.!: AAUS DC WORKSHOP. U.S.C. Sea Grant Pmgram, Los Angeles, CA, 1989 EDGE ownersreturn warrantycards for 65% of all units sold.They are,in general, olderdivers who can afford the more expensive computer, with 56%over 35 yearsof age, andonly 7% younger than 25. They report an outstanding number of divesper year, the databaseaverage is 82for thosewho responded. The different age groups report different averages,with the under 25 group at 101dives/year, the 25-35 group at 91 dives/year, and theover 35 group at 75 dives/year,This is understandable,since many EDGE owners take multiple,intensive dive trips each year, and justify the expense of theinstrument by the increaseddiving that it provides. SkinnyDipperowners only return warranty cards representing less than 30% of all unitssold. They have a similarage distribution to EDGEowners, with 7% under 25, 33% 25-35,and 60% over 35. They report a smallernumber of divesper year, with a database averageof 62.The averages for thedifferent age groups is alsoless than the corresponding EDGEgroup, with the under 25 group making 65 dives/year, the 25-35 group making 75, and the over 35 group making 54. This informationon the agedistribution and diving frequency of ORCAcomputer ownersallows us to estimatethe number of divesrepresented by thewarranty database. It is assumedthat each computer only makeshalf thenormal dives during the year that it is purchased,except for SkinnyDippersin 1987, which are only given 25% of annualdives due to late release.The individuals in the databasenot reporting ageand dive information axeassumed to have a similar distribution to thosewho did report. Finally, the average numberof divesper year for eachage group is assumedto be 50 dives/yearfor each EDGE,and 38 dives/yearfor eachSkinnyDipper in the field for the full year.All assumptionsarechosen to beconservative, soas to underestimatethenumber of dives performed. Includingonly warranty data, and not dives by theentire owner population, at the end of 1987there had been207,000 dives on EDGE, and 12,900dives on SkinnyDipper. At theend of 1988,only within the warranty database, EDGE will havelogged 430,000, andSkinnyDipper 112,600. This data is presentedin spreadsheet form in theappendix. The analysisof cumulativedives can be extendedto the entireORCA computer ownerpopulation. Those owners not represented in the warranty database are assumed to besimilarly distributed to thosewho returned warranty cards, In makingthis estimation, productionrecords are used to represent the number of newcomputers in the field each year.Computers using the ORCA model made by other manufacturers arenot included in this analysis.Other assumptions are identical to thosemade in thewarranty database calculations. Figure1 showsthe estimated cumulative dives for all ORCAcomputers from 1983 to the end of 1988.Contributions from the threedifferent age groupsand both computers areshown. The steady growth of EDGEdives can be seen, with cumulative totals of only 30,000in 1984,115,000 in 1985,274,350 in 1986,and 584,725 by theend of 1987.By the end of 1988,EDGE dives will havereached over one million. The influenceof SkinnyDipperis seenbeginning in 1987,with 50,000additional dives on theORCA model,for a cumulativetotal of over635,000. With 466,000SkinnyDipper dives by the end of 1988,there will havebeen over 1.5million divesmade on the ORCA model. AlthoughFigure 1 alsoshows the breakdown of divesby agegroup, in additionto computertype, it is difficultto seethe exact distribution of agegroup. Figure 2 displays thisdata directly, showing that, for theyear-end 1988 data, 57% of thedives are made by the over-35group, 36% by the 25-35 group,and only 6% by the under-25group. 36 Heimniller.Orca Industries'Dive Computers While it is not possible to place an exact number on the size of the ORCA decompressionmodel diving exposure, these extremely conservative estimates can give us a generalidea of the scale involved. Figure i. Cumulativedives on ORCA computers 1984 I 988 1.60 1.50 1.40 1.30 V! 1.20 Z 0 1,10 1.00 0.90 o.eo 0. 70 o. 60 0.50 0. 40 0.30 O.20 0.10 0.00 1984 1986 1987 I 988 DIVliNGYEAR BENDS INCIDENCE At the1988 Annual Scientific Meeting of theUndersea and Hyperbaric Medical Society,Joel Dovenbarger presented a paper prepared by Vann, Dovenbarger, Wachholz, andBennett, discussing dive computer bends cases. There were 38 cases, effective year- end 1987,experienced by usersof divecomputers. Cases of obvioususer error were discarded,aswere inappropriate reports such as that of theperson diving with a buddy whowore an EDGE. All 38cases were not attributable to persons wearing EDGE or SkinnyDipper,as other computers are available. For thepurposes of discussion,let us assumethat all caseswere marks against the ORCA decompression model, or theuse of modelbased dive computersin general. In hisFebruary 1988 Diving Medicine Column in SkinDiver Magazine, Dr. Fred Bovecites bends incidence figures for the useof the U.S.Navy Standard Air DecompressionTables. The source of his figuresand the assumptions involved is not mentioned.It is notunreasonable to assume that the figures represent the gross bends incidenceattributable to theNavy tables within the Navy diving population. Furthermore, weshould note that these figures are based on people diving the tables in thereal world, withwhatever errors and fudge factors this involves. His figures are 9 casesper 100,000 divesfor diveswithin the no-decompression limits, and 38 casesper 100,000dives for decompressiondives. The U.S. Navy makes predominantly single no-decompression dives,with singledecompression dives less common, The Navy tends not to make Langand Hamilton Kds.!: AAUS DC W'ORKSHOP.U.S.C. Sea Grant Program, Los AngeLes, CA, 1989 repetitive,multi-level, no-decompression dives over a numberof consecutivediving days, which is extremelycomttion to recreationaldiving vacations. Figure 2. Distribution of cumulative ORCA dives BY AGE GROUP,YEAR END 1988 UNDER25 .4'! 25-W 6.l X! OVER35 7.2K! Using the cumulativedives on the ORCA modeland the numberof reportedbends casesat year-end 1987, the gross bendsincidence of the ORCA model is 6 casesper 100,000 dives. Since this is for all dives, not just no-decompression,it does not corresponddirectly with either of the U.S. Navy statistics.It comparesfavorably with the 9 cases/100,000Navy no-decompressionfigure, and is one-sixth of the decompression dive figure. This is in spiteof the typical computervacation dive history of 3-5 multi-level dives per day, for five to fourteen day trips. These numbers can only provide a conservativerough estimate, given the errors of reporting and the uncertainty of the denominator,but they leadus to acceptthe ORCA decompressionmodel for the depthsand exposurestypical for recreationaldivers. ORCA PHILOSOPHY ORCA is constantlyalert for ways to fine-tunethe hardwareor the decompression modelto the benefitof recreationaldivers. The EDGE/SkinnyDipperalgorithm is not valid at altitudesabove 2000 feet, as it becomesless