Pendulum Search Pattern

The pendulum search pattern was designed to optimise the time spent searching in the most likely area of finding the casualty.  It could be seen as half of the expanding box pattern, but where the rescue vessel first performs a rectangle search around the datum point and along the drift path.  Once this has been done, none of the search time is spent up-drift of the DATUM position.

Note : Due to the way the pattern is designed, it can be used to find a fast moving casualty that will not deviate much, or it can equally well be used for a slow moving casualty that might deviate lots.  This is dictated by the leg length and the track spacing as shown in the diagram below.

•The red route takes the shortest time and is for a casualty that is drifting fast.  The leg length is longer than the track spacing.  The rescue vessel is kept “tight” near the drift path, and is moved along the drift path quickly.

•The yellow route is really half a square – the leg length and the track spacing are the same

•The green route is for a slow drifting casualty that can diverge a lot – the leg length is smaller than the track spacing, and this route takes the longest period of time to complete.

The pendulum search is ideal for splitting up and allocating to different vessels in a multi-vessel search.

•A : The Datum or Start position which can come from

otype in your own coordinates (see Coordinate input in the Important information section) and they will the point at which the pattern will start

opreviously calculated Datum positions - when you click on the circle to the left of "Calculated Coordinate" a list of the last calculated Datum positions is displayed and you can select the one you need by clicking on it.  In this case the LKP position related to the Datum is displayed

•B : Distance from Datum : normally an Expanding Box search is started at the Datum position, and so the default value of zero is fine.  If you want to though

ostart closer to the LKP position (up-drift) then enter a negative number of nautical miles

ostart down-drift of the Datum position then enter a positive number of nautical miles

•C : The drift bearing which will guide the bearing of the pattern. 

oIf you entered your own Start Coordinates, you must enter your own bearing.  

oIf you selected a previously calculated Datum position then the drift bearing from that calculation will be displayed

•D : The speed the rescue vessel will average during the pattern execution

•E : Search Minutes - this defaults to 60 minutes but can be changed as required.  It is used with the RV Speed to calculate how many legs of the pattern can be searched in the given search time

•F : The leg distance - this is compulsory for an Pendulum pattern

•G : Track spacing - this is compulsory for a Pendulum pattern

•H : Arc Angle - this is not used with the Pendulum pattern

•I : clicking on this "Calculate" button will calculate the search patterns using the information in the header

•J : Click on the Pendulum radio button

•K : the details of each leg of the pattern

oUse - this column contains "y" by default and it means that the leg will be included in the GPX file that is created and sent to the vessel (see Multi-vessel searches)

oLeg - the leg number

oDist - the distance of the leg in nm

oBear - the bearing of the leg from leg start point to leg end point

oMins - the number of minutes the leg will take to complete given the rescue vessel speed

oTot Mins - the total number to minutes that will have been used to get to the end point of the leg

oDD Coords - the coordinates of the turning point in Decimal Degrees

oDDM Coords - the coordinate of the turning point in Degrees and Decimal Minutes 

•L : Use All - clicking on this will change the value in the "Use" column.  The default is that all the values in this column = "y", and if the "Use All" check box is clicked and the "y" values will be replaced with blank values.  If the values are currently blank, they will be replaced with "y" when the check box is clicked. (for more details see Multi-vessel searches)

•M : Total Stats : this section shows the total statistics for the entire calculated pattern

oThe number of minutes it will take for the entire pattern to be executed given the average speed of the vessel

oThe time it will take in hours and minutes

oThe distance traveled for the entire pattern

oThe area covered by the search pattern

•N : Click on this GPX button to create a GPX file that will include the selected legs of the pattern 

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