Arc Angle

The angle used instead of a leg length for the Expanding Parallel Line search pattern. 

It is used mainly when there is a fast moving current, eg at a river estuary, that takes a casualty away from the LKP fast, but the speed lessens with distance from the river mouth, and the likelihood of the casualty diverging increases as the speed of drift lessens.

Bearing

The direction of one point with respect to another point or the direction of motion, measured  clockwise from North (Magnetic or True), in degrees

Caller

The person who alerts the rescue organisation to the fact that someone is needing assistance

Casualty

The person or vessel that is requiring assistance from the rescue organisation

Compound Datum

A compound datum is used when a casualty has been missing for quite a time, and we are needing to calculate where it is at a particular time as accurately as possible.  If the forecast wind and current conditions are being used to calculate the datum, we collect the forecast conditions from the time of the LKP to the time of the datum, and we use these to plot the drift path.  

It is recommended that a one hour time period is used when calculating a compound datum position

Coordinate

A unique identifier of a precise geographic location on the earth, usually expressed in alphanumeric characters and being made up of the Latitude followed by the Longitude in degrees, degrees and decimal minutes or degrees, minutes and seconds.  If the North (N), South (S), East (E) and West (W) are omitted, any number in the southern and in the western hemispheres is given as a negative number.

34.5°S, 018.25°E  =  34° 30'S, 018° 15'E  =  -34.5°, 018.15

Creeping Line Pattern

Another name for the Parallel Line search pattern.

Current direction

We use the surface current in the sea to help us calculate the effect of the conditions on the speed and direction a casualty might drift.  The names of the direction are the same as the cardinal points - but it is important to remember that the current is named using the direction it is GOING TO.

Datum

The point where we estimate we will find the casualty when the rescue team arrives in the area.  In order to calculate it we need to know -

•LKP

•Drift Time

•Conditions from

oTest Drift

oLeeway table, wind and surface current

Divergence Angle

Sometimes referred to as "leeway divergence" as it describes the amount that a casualty may drift to the left or right of the prevailing wind direction.  This depends on a number of things -

•casualty type and condition

•speed of the wind

Down drift

This is that part of the drift path that is in the direction of drift after the LKP

Down wind

In the same direction as the wind.

Drift path

The direction in which it is estimated the casualty is drifting.

Expanding Box Pattern

A search pattern that is used to cover a large area if there is minimal drift in the area.  The leg length is normally the same as the sweep width, and each turn is a 90° turn.

Expanded Parallel Line Pattern

This search pattern is often used where there is a fast drift speed which lessens in time eg at the mouth of a fast flowing river.

Extended Search Area

If the drift time is longer than about an hour it is recommended to use the Extended Search Area

Flanking Station

If a station is located close to another station and their operational areas overlap, they are call flanking stations

Goal Keeper Pattern

This pattern is normally used where the drift speed is high.  The search vessel travels up and down the down drift side of the search area and waits for the casualty to drift into them.  It is often used in a multi-vessel search.

Google Earth Pro

This is the free, internet based mapping software that we recommend SearchWell users use to verify waypoints and routes, and to assist in finding out coordinates, distances and bearings.

GPX file

SearchWell creates navigational commands which it stores in GPX files.  These files are read by far the majority of navigational devices and software.

Last Known Position (LKP)

This point is the last seen position of the casualty.

Leeway Table

This table contains formulae for calculating the effect of wind on the casualty drift, and also the divergence angle.  Both of these depend upon the casualty type.

Leg Length

The distance the rescue vessel will travel on a normal leg of a search pattern.

Magnetic Bearing

Sometimes referred to as "Compass bearing".  The bearing relative to the magnetic north pole measured clockwise.

Magnetic Declination

The angle between magnetic north and true north.  Magnetic declination varies from place to place, and is constantly changing with time.

Magnetic Variation

Sometimes referred to as "magnetic deviation".  It is the effect of interference from magnetic fields created by the vessel's own equipment on the compass reading, and is unique to every vessel.

Multi Vessel Search

When more than one vessel is used to search for one casualty.  In SearchWell we can allocate different search patterns in the expanded search area to different vessels, or we can split one search pattern into legs that can safely be performed by different vessels.

Multi-User

SearchWell allows for single-users and multi-users.  Single users can only change the information that is pertinent to the individual station, where a multi-user can change the information for all stations and also for the organisation (eg Region table)

Parallel Line Pattern

This pattern is used when the drift in the search area is minimal and the casualty could be anywhere in the search area.  The long legs will cross over the estimated drift path at 90°, and the short legs will be parallel to the estimated drift path.

Pendulum Search Pattern

The pendulum search pattern was designed by SearchWell to optimise time spent searching in the areas with the greatest probability of finding the casualty.  The parameters that are used to define the search can cater for a fast moving casualty or a slow moving casualty.

Rapid Search Area

This is the search area that should be searched in the first hour or so of a search.

SearchWell offers two ways of naming the Rapid Search Area -

•The international standard where point "A" is the north most point

•Where the line "A-B" indicates the direction of drift as it is down drift from the Datum position

Rendezvous

This point is the most efficient point for two moving objects to meet - given that they are traveling at two different speeds and on different bearings.

Reverse Compound Datum

The reverse compound datum calculates where a casualty might have drifted FROM.  An example would be that we have a report of a drifting abandoned vessel, and we need to calculate what it's most likely drift path and speed was.  

Route

A number of points that are linked to define the path a vessel should travel.

Sector Search Pattern

The sector search is a simple, rapid response pattern that is often performed at the start of a search.  If the casualty is not spotted during the original pattern, a new Datum can be calculated and the sector search pattern can be rotated by 30° and the leg length doubled.

Sweep Width

The distance on either side of the vessel that the crew would be able to see the casualty.  It relates to the Track Spacing which must be less or equal to the sweep width

System table

SearchWell stores information in "tables".  There are a number of tables -

•Region table - which contains the name of the region's manager and their cell number

•Station table - storing the default information for the station

•Waypoint table - storing the information for known points (at sea and on land) in the operational area

•Contact table - the names and contact numbers of people and organisations that are important to the station

Test Drift

An accurate method of calculating the direction and speed of drift in the search area.  There are some important considerations that affect the usefulness of a test drift -

•it should be performed as close to the LKP area as possible

•it should be performed as soon as possible so that the conditions have changed as little as is possible

•the test drift should be performed by an item as similar as possible to the casualty

Track Spacing

The distance between the legs of a search pattern.  This must be less than, or equal to, the Sweep width

True bearing

The bearing relative to the True North pole, measured clockwise.

Up drift

This is that part of the drift path that is in the opposite direction of drift

Up wind

In the opposite direction as the wind.

Waypoint

A single point defined by Latitude and Longitude.

Wind direction

The name of the direction is the same as the cardinal points - it is important to remember that the wind is named using the direction is is COMING FROM.