11.8 Expanding Square Search Pattern
Purpose
To outline the use of expanding square search patterns during search and rescue (SAR) operations involving SLS personnel, services, and assets.
Overview
An expanding square search pattern is a structured search method that begins at the reported position, last known position, or most probable location of the search object and expands outwards in a square pattern.
The National Search and Rescue Manual refers to this as an expanding square search.
SMAR and Surf Life Saving training material may also refer to this as an expanding box search. For consistency with NATSAR terminology, this SOP uses the term expanding square search pattern.
An expanding square search pattern is best suited where:
- The search object is believed to be in a relatively small area,
- The last known position or most probable location is reasonably accurate,
- The current, wind, or drift direction is unknown or uncertain,
- Accurate navigation or timing can be maintained, and
- Uniform outward coverage from a central point is required.
The pattern may be conducted by one or more Search Teams, including IRB, RWC, JRB, other approved powercraft, in-water personnel, aircraft, vehicles, or land-based personnel where appropriate.
In South Australia, South Australia Police (SAPOL) is the control agency for all search and rescue activities. SLS personnel may conduct or support expanding square search activity where tasked, authorised, trained, equipped, and operating within approved capability.
SAR activity should be undertaken in accordance with the National Search and Rescue Manual, Control Agency direction, and SLSSA Standard Operating Procedures.
Diagram
Definitions
Expanding square search pattern means a search pattern that begins at or near the reported position, last known position, or most probable location and expands outwards in successive square legs.
Expanding box search means the same general search pattern described as an expanding square search, using terminology commonly seen in some Surf Life Saving and SMAR material.
Search Team means a person, team, vessel, aircraft, vehicle, or other resource tasked to undertake SAR activity.
Search area means the defined area assigned for search activity.
Search leg means one straight section of the search pattern.
Track spacing means the distance between adjacent search legs.
Last Known Position (LKP) means the last confirmed location where the person, vessel, craft, object, or search target was seen or known to be.
Datum means the reference point from which a search pattern is commenced or calculated. For this SOP, this may be the last known position, reported position, most probable location, marker buoy, GPS point, or other assigned reference point.
Search object means the person, vessel, craft, object, or item being searched for.
Procedure
When to Use
An expanding square search pattern may be used where:
- The last known position or most probable location is known with reasonable accuracy,
- The search object is believed to be within a relatively small area,
- The search should begin at a central point and expand outward,
- Current, wind, or drift direction is unknown or uncertain,
- Search Teams can safely maintain the required pattern,
- Track spacing can be maintained,
- Communications can be maintained,
- The search area and pattern have been assigned by the Control Agency or approved SLS command role, and
- SLS resources are capable of safely conducting the task.
An expanding square search should not be used where the last known position or most probable location is unreliable, the search area is large, or the Search Team cannot maintain accurate navigation, timing, or spacing.
Search Planning
Where SAPOL or another authorised Control Agency has assumed control, search planning remains the responsibility of the Control Agency.
SLSSA may support search planning by providing:
- Last known position information,
- Witness information,
- Local beach and coastal knowledge,
- Surf, wind, tide, current, and drift observations,
- Search object information,
- SLS resource availability,
- Asset capability and limitation information,
- Communications information, and
- Risk or safety considerations.
SLS personnel must not independently develop or implement a complex SAR search plan where the Control Agency has assumed control, unless directed or authorised to do so.
Pattern Description
The expanding square search pattern begins at or near the last known position or most probable location.
The Search Team then travels a series of straight search legs with 90 degree turns between legs.
The first two search legs are normally equal to one track spacing.
Each following pair of search legs is increased by one additional track spacing.
The pattern continues to expand outward until:
- The search object is located,
- The assigned search area is complete,
- The Search Team is retasked,
- Conditions become unsafe,
- The search is modified,
- The search is suspended, or
- The Search Team is stood down.
The pattern may be turned to the left or right depending on the search area, environmental conditions, observer position, vessel handling, or Control Agency direction.
Starting Point
The starting point should be confirmed before commencing the pattern.
The starting point may be:
- The last known position,
- The point last seen,
- The reported position,
- The most probable location,
- A datum assigned by the Control Agency,
- A GPS point,
- A buoy or surface marker,
- A tube marker,
- A visual reference, or
- Another approved reference point.
Where safe and appropriate, a buoy, tube marker, GPS point, or other visual reference may be used to help maintain the pattern.
Markers must not create additional hazards or interfere with other vessels, aircraft, swimmers, Search Teams, or emergency service operations.
Expanding Square Method
When conducting an expanding square search, the Search Team should:
- Confirm the assigned search area.
- Confirm the search object.
- Confirm the starting point or datum.
- Confirm the initial direction of travel.
- Confirm whether turns will be made to the left or right.
- Confirm track spacing.
- Confirm search speed or timing.
- Confirm communications arrangements.
- Confirm SITREP requirements.
- Proceed to the assigned starting point.
- Commence the first search leg from the starting point.
- Travel one track spacing.
- Turn 90 degrees in the assigned direction.
- Travel one track spacing.
- Turn 90 degrees in the assigned direction.
- Travel two track spacings.
- Turn 90 degrees in the assigned direction.
- Travel two track spacings.
- Continue the pattern, increasing each following pair of legs by one track spacing.
- Maintain observation throughout each search leg.
- Record areas searched and any sightings, clues, hazards, or limitations.
- Provide updates to the State Operations Centre (SOC) as required.
Where practical, search tracks should be recorded using GPS, mapping, or other available tracking tools.
Distance, Time and Speed Control
The expanding square search pattern relies on accurate leg length and consistent turns.
Search leg length may be managed by:
- Distance,
- Time and speed,
- GPS or mapping tools,
- Visual references,
- Buoy or marker references,
- Landmark references, or
- Other approved navigation methods.
Where using distance, each pair of search legs should be equal in length and each following pair should increase by one track spacing.
Where using time and speed, each pair of search legs should be conducted at the same speed and for the same time, with each following pair increased by the required amount.
Where the search object may be drifting, timing and speed relative to the water may be more useful than relying only on fixed ground-based or GPS positions.
Search Teams should report any concern that they cannot maintain accurate leg length, timing, heading, or track spacing.
IRB, RWC, JRB or Other Powercraft Method
Where an expanding square search is conducted by IRB, RWC, JRB, or other approved powercraft, the Search Team should:
- Confirm the search area before entering the pattern,
- Confirm the starting point or datum,
- Maintain safe search speed,
- Maintain accurate 90 degree turns,
- Maintain the assigned track spacing,
- Maintain effective lookout at all times,
- Avoid excessive speed or manoeuvring that reduces detection,
- Maintain awareness of other Search Teams,
- Maintain safe separation from swimmers, in-water personnel, other vessels, and the public,
- Consider wind, tide, current, swell, and drift,
- Consider fuel range and endurance,
- Report any area that cannot be searched safely, and
- Provide SITREPs as required.
Where powercraft and in-water personnel are operating in or near the same search area, specific separation, communication, and safety arrangements must be confirmed before commencing the search.
In-Water Search Team Method
Where an expanding square search is conducted by in-water personnel, the Search Team should:
- Confirm the search area and boundaries,
- Confirm the starting point or datum,
- Confirm the initial direction of travel,
- Confirm whether turns will be made to the left or right,
- Confirm spacing between searchers,
- Maintain formation where required,
- Maintain visual or verbal contact where practicable,
- Maintain agreed search speed,
- Maintain awareness of fatigue and exposure,
- Maintain awareness of current, wind, wave action, and drift,
- Avoid entering areas beyond capability,
- Report hazards or limitations,
- Report any areas not searched, and
- Provide SITREPs as required.
In-water expanding square searches should only be undertaken where conditions, supervision, support, communications, and risk controls are suitable.
Multiple Search Teams
An expanding square search is normally most effective when a Search Team can maintain the pattern from a central point without interference.
Where multiple Search Teams are involved:
- The Control Agency or approved SLS command role should assign clear search areas,
- Search Teams should not duplicate the same expanding square pattern unless specifically directed,
- Separate search areas or sectors should be allocated where practicable,
- Track spacing must be clearly understood,
- Communications must be maintained,
- Search Teams must remain aware of each other’s location,
- Search areas completed by each Search Team must be recorded, and
- The SOC or coordinating role must be updated as search areas are completed.
Where Search Teams include a mix of powercraft and in-water personnel, separation arrangements and powercraft safety controls must be clearly briefed.
Track Spacing
Track spacing should be determined by the Control Agency or search planning role where the SAR operation is under agency control.
Track spacing should consider:
- Search object size,
- Visibility,
- Water clarity,
- Sea state,
- Surf conditions,
- Wind,
- Glare,
- Observer height,
- Search speed,
- Available Search Teams,
- Search area size,
- Fatigue,
- Probability of detection,
- Available daylight, and
- Operational risk.
If visibility or detection conditions deteriorate, track spacing may need to be reduced or the task may need to be modified.
SLS personnel should report any concern that the assigned track spacing is unsuitable or unsafe.
Visual References and Markers
Search Teams may use visual references, GPS points, mapping tools, buoys, landmarks, dye markers, tube markers, or other approved methods to support accurate navigation and coverage.
Where safe and appropriate, a buoy or surface marker may be used to identify the last known position, datum, or another reference point.
Markers must not create additional hazards or interfere with other vessels, aircraft, swimmers, Search Teams, or emergency service operations.
Communications and SITREPs
Before commencing the search, the Search Team should confirm:
- Search area,
- Starting point or datum,
- Initial direction of travel,
- Turn direction,
- Track spacing,
- Search speed,
- Radio channel,
- Call signs,
- SITREP frequency,
- Emergency process,
- What to do if the search object is located, and
- What to do if the task cannot be completed.
SITREPs should include:
- Current location,
- Search progress,
- Search legs completed,
- Areas covered,
- Conditions,
- Current, wind, or drift observations,
- Sightings or clues,
- Hazards,
- Resource status,
- Personnel fatigue or welfare concerns,
- Any change in capability, and
- Task completion.
Working with Powercraft
Where in-water personnel are operating with or near IRB, RWC, JRB, or other approved powercraft, the relevant powercraft safety controls must be applied.
This may include:
- Clear separation between powercraft and in-water Search Teams,
- Confirmed powercraft operating areas,
- Confirmed communications or hand signals,
- Safe speed near in-water personnel,
- Active lookout,
- Engine safety when close to in-water personnel,
- Emergency stop or withdrawal signals, and
- Immediate modification or cessation of the task if safety cannot be maintained.
Safety Considerations
Personnel conducting an expanding square search must maintain awareness of:
- Surf, swell, wind, tide, current, and drift,
- Other vessels or water users,
- Aircraft or RPAS activity,
- Reduced visibility,
- Sun glare,
- Fatigue,
- Communications limitations,
- Navigation errors,
- Inaccurate timing,
- Pattern distortion,
- Collision risk,
- Search Team separation,
- Crew position and lookout effectiveness,
- Fuel or battery limitations,
- Access and egress, and
- Changes in environmental conditions.
Search activity must be managed using a risk versus gain approach.
SLS personnel must not continue a search task where conditions become unsafe or the task exceeds approved capability.
Locating the Search Object
If the person, vessel, craft, object, or clue is located, personnel should:
- Mark or record the location,
- Notify the SOC immediately,
- Provide a SITREP,
- Commence rescue or emergency care where safe and appropriate,
- Maintain observation if immediate rescue is not possible,
- Preserve potential evidence where required,
- Avoid disturbing the scene unless required to save life or prevent further harm, and
- Follow Control Agency or SLS command direction.
Completion of Search Area
When the assigned search area is complete, the Search Team should notify the SOC or coordinating role.
The update should include:
- Search area completed,
- Time commenced and completed,
- Search pattern used,
- Search legs completed,
- Search tracks or route,
- Conditions during the search,
- Any areas not searched,
- Any sightings or clues,
- Hazards or limitations,
- Personnel or equipment issues, and
- Whether the Search Team is available for further tasking.
Records
Search activity should be recorded where practicable.
Records may include:
- Assigned search area,
- Starting point or datum,
- Last known position,
- Start and finish times,
- Search tracks,
- GPS records,
- Search speed,
- Track spacing,
- Search Teams involved,
- Sightings or clues,
- Areas unable to be searched,
- SITREPs,
- Safety concerns,
- Task modifications, and
- Stand down instructions.
Records should be provided to the SOC for inclusion in the incident log.
References