Scuba Diving

1
Scuba Diving Example Application

• Yaji Sripada

2
Scuba

• Scuba Self Contained Under-water Breathing
  Apparatus
• Scuba diving popular form of recreational
  diving
• 1 million divers get certified every year
• Safety of all these divers is a serious issue
• By diving carelessly, divers suffer from
  decompression illness (DCI), more popularly the
  bends

SCUBA Diver
3
Decompression Illness (DCI)

• Possible explanation of DCI bubble theory
• Nitrogen from air absorbed by body tissue because
  of the water pressure
• When diver rapidly ascends the dissolved Nitrogen
  forms bubbles
• Large bubbles that clog joints cause pain and
  bends
• Individual variation of DCI
• Some don't get bent when they "should," others do
  get bent when they "shouldn't."

4
Dive Tables

• Traditionally dive tables are used for planning
  dives to avoid risk of DCI
• Dive tables contain safety limits of depth and
  time
• There are many standard dive tables,
• Original UK, US Navy etc.
• Dive tables can be generated by an algorithm
  many variations possible
• Dive computers run these algorithms and generate
  dive tables on the fly

5
Dive Tables
6
Dive Computer (DC)

• Scuba divers wear dive computers
• DC guides the divers to carry out safe dives
• DC records logs of dives consisting of
• Log of all dives and
• For each dive the following data
• Time series of dive depth called dive profile
• Time series of Tissue saturation
• Temperature
• SCUBA equipment
• etc
• Dive logs from a DC can be downloaded to a PC

7
Dive Computer Data

• DCs are equipped with software to view dive log
  data as shown here
• Divers are expected to analyse their dives to
  learn about their safety.
• For example, the dive shown here is an unsafe
  dive because the diver performed a deeper dive
  the second time.

8
Safety of a Dive

• Is complicated to determine
• Depends at least on
• Diver characteristics such as age, general
  health, history of dive related illnesses
• Dive characteristics dive profile (depth-time)
  data, gas mix and dive plan
• Dive environment temperature and altitude

9
Project Dive Exploration (PDE)

• PDE is a large scale research project sponsored
  by Divers Alert Network (DAN)
• PDE collects data (medical history, dive profile
  etc) corresponding to large numbers of real dives
  and their medical outcomes.
• PDE analyses these data to learn the relationship
  between features of dive data and DCI (or any
  other medical condition)
• PDE hopes to develop the science required to
  label dives as SAFE or UNSAFE (binary classifier)

10
Understanding Dive Computer Data

• PDE is ongoing and results are expected in the
  future
• Until then divers have to manually inspect dive
  data to determine the safety of their dives
• The community of divers is very diverse
• Many of them may not possess the skills required
  to use the vendor supplied software
• We need to help divers better understand their
  dives.
• We use this application as one of the example
  domains in this course

11
Analysis of dive data

• To determine unsafe dives
• The following patterns in dive profiles are known
  to cause DCI
• Rapid ascent
• Sawtooth
• Unnecessary stops
• Reverse dive profile etc.

12
Segmenting a profile into zones
13
Rapid Ascent

• A pattern in the dive profile caused by the diver
  rising rapidly to the surface
• Rapid ascent is the most critical factor causing
  bubbles in body tissues
• Therefore has higher chance of causing DCI
• Most dive computer software detect rapid ascents
  and sound alarms

14
Sawtooth

• A pattern in the dive profile caused by the diver
  going down and up in quick succession
• This may not happen very frequently, but when it
  happens it may cause the tissues to absorb excess
  gas bubbles
• Therefore may cause DCI
• Dive computer software does not detect them

15
Reverse Profile

• This is a pattern observed at the level of a
  whole dive profile.
• Ideally a diver is required to initially reach
  the planned maximum depth and then all the
  subsequent dive should be performed at a depth
  shallower than the maximum
• A reverse profile is a dive profile where the
  diver performs the reverse of the ideal

16
ScubaText Communication of dive data

• A research project in the department
• We explore effective ways of presenting the
  results of data analysis
• For scuba divers
• For scuba instructors
• For health professionals attending to divers
• For general public (dive blogs)
• Using visualizations and Text

17
ScubaText Prototype
Data Analysis analysing raw data for required
features/patterns Data Interpretation mapping
the data features/patterns to the actual dive
features and rating the dive based on the dive
features e.g. long bottom times receive low rating
18
Example Dive- Dive Context

• Date Mon, 04/10/1993 Location Elba
• Time 1537 Site Capo dArco
• Altitude range 0m900m Interval 0005
• Weather Cloudy Air Temp not recorded
• Dive suit two pc. Wetsuit Tank Size 14.0l
• Maximum Depth 48.0m Dive Time 0047
• Min. temperature 190C Air consumption131bar
• Dive Type Decompression, single ascent, sea
  water
• Activities Sightseeing
• Alarms None
• Buddies YYY
• Max ascent time 10

19
TextAnnotated Graphics (D)
Risky dive with some minor problems. Because your
bottom time of 12.0min exceeds no-stop limit by
4.0min this dive is risky. But you performed the
ascent well. Your buoyancy control in the bottom
zone was poor as indicated by saw tooth
patterns marked A on the depth-time profile.
20
Text and Graph

• Text mainly communicates a safety message
• Risky dive, Safe dive etc.
• Uses dive features inferred from raw dive data to
  explain the main message
• Links data features to dive features as further
  explanation
• E.g. saw tooth pattern linked to poor buoyancy
  control
• But not all the terms referring to data features
  do not have universally accepted definitions
• Bottom time, bottom zone etc
• Graph provides semantic grounding for these terms
• Text and graph are linked
• References to annotations in the graph

21
Summary

• Dive computers record dive data
• Not possible to label dives SAFE or UNSAFE
  automatically
• Divers need help of novel technology to explore
  their dives
• Detect unsafe patterns
• Present the results
• Graphically
• Textually