Figure 1: Trial of the SeaSlate on the Great Barrier Reef

Each SeaSlate (Figure 1) consists of an off-the-shelf pen computer (with inbuilt LCD screen) which has been housed in a clear waterproof casing. It has two external handles one of which incorporates a 6-button Kord® Grip that is used to operate the computer. The Kord® Grip can be swapped to either side of the housing for ambidextrous . The housing (which is rated to 30m depth) has a removable side door and an external serial port so that data can be uploaded to a desktop computer or the SeaSlate can receive input from another technology (e.g. GPS). An external socket has been provided so that batteries can be recharged without having to open the casing. The SeaSlate also has an inbuilt pressure sensor which automatically logs depth.

The diver holds the SeaSlate by its two grips (with elbows resting on the side wings) so that the screen is immediately in the field of view. Field trials have shown that the computer can be steered using one hand and the computer can be easily operated (using gloves) even whilst swimming.

In its present configuration the SeaSlate receives position information for diver navigation via an underwater GPS (or DGPS) with surface antenna which is connected to a external serial port. The GPS is connected via a cable to a small floating antenna system (Figure 2). The diver’s swim path is plotted on the SeaSlate’s display using data (in the form of a NMEA stream) from the GPS. The diver is also able to log object positions which may be encountered during the swim, as well as access a small database of mine types (with pictures). All this is done using five buttons on the Kord® Grip. The software has a variety of other features which allow: divers to: flip the search grid (so that the diver is moving in the same direction as the icon on the screen), zoom the map (five levels), and transfer data (to a desktop PC).

Figure 2: SeaSlate being used by Navy divers

CSearch 
This program takes GPS output and plots the diver’s position (as a continuous track - Figure 3) within a search grid which is projected on the display (obviating the need for divers to use jack-stays, marker buoys, etc.). The program also provides divers with their distance (in x,y metres) from the datum. The parameters of the search can be manually entered by the diver prior to the mission. They include: datum (latitude, longitude), bearing, search width, lane width, box length and width), and position in search lane (centre, left, right). Divers can also log the position (and depth) of any objects that they may encounter during a search.


Figure 3: CSearch Interface showing swim path and logged objects

The present version of CSearch gives divers 3 types of objects to choose from: mine, non-mine, and unknown. If it is a mine then the diver is able to consult an EOD Reference Database (see below) to verify the mine type. Once this has been done the mine type can be logged and the search continued. The search grid has 4 levels of zoom so that divers can focus on either their current lane through to several lanes at a time. The data logged during the mission can be transferred to an RAN Database virtually with the push of a button.

EOD Reference Database 
This database enables RAN divers to look at diagrams of ordnance to assist in the identification of those mines which are encountered during a search. The diagrams have been incorporated within a chordic graphical user interface (CGUI) so that divers can scroll through them easily underwater.

Environmental Database 
This is a database which allows RAN divers to directly enter environmental data into the computer and so do away with the need to record it on paper first. The parameters which divers are able to record are: bottom material description (mud, clay, sand, gravel, coral, vegetation, shell and rocks), particle size (<1mm, <2mm, >2mm), bottom roughness (smooth, boulders, ripples, ridges and mounds), bottom hardness (1 arm thrust, 2 arm thrusts, 3 arm thrusts), number of objects (>600mm) in 15m circle, sonar radius (m), and number of objects detected.

Original Prototype Specifications - 1997
Computer:
· Dauphin DTR-1 Pen Computer, Cyrix 486SLC 25 MHz microprocessor, 8MBDRAM, 40MB HDD
· Backlit passive matrix LCD 640 x 480 VGA display, 80 column display, 64 shades of grey
· bi-directional DB-25f Parallel port, 9 pin RS-232c Serial port
· Power: Advanced power management features, Internal 7.2 volts NiMH battery with 6 hour life
· Physical dimensions: external: 9" x 5.5" x 1.25", weight: 1.1 kgs (2.5lbs), including battery

Software:
· Operating System: MS - Windows
· CGUI: CSearch, Explosive Ordnance Disposal (EOD) Reference Database, Environmental Database,

Housing:
· Clear acrylic, Box Dimensions - 370mm x 205mm x 122mm, 19mm wall thickness, Base Panel
Dimensions - 386mm x 588mm, 10mm wall thickness

Kord® Grip:
· 5 Hall effect switches set inside a molded epoxy hand grip, Button-removal for cleaning inside switches

Pressure Sensor:
· Penny and Giles 0-7 Bar absolute sensor, accuracy 0.2%, Factory calibrated and
interchangeable with a stainless steel diaphragm.

Depth Rating:
- Housing: - 30m
- Kord® Grip: - unlimited

Other:
- Unknown magnetic signature, 0.45kg (1lb) buoyancy in seawater, total weight of 8.5kgs (19lbs),