Maritime Search Patterns
IAMSAR Search Pattern Visualiser & Tactical Planning Engine
Watch how each standard IAMSAR search pattern is run by a single search and rescue unit (SRU), then by two, three and four rescue boats working together. Pick a pattern, choose how many SRUs, and press Play. Hover over any part of the drawing for a short note. A lifeguard circle search for beach rescue is included too.
Datum
The most probable position of the search object, corrected for drift.
Track spacing (S)
Distance between neighbouring search legs. Smaller S means better coverage but more time.
Commence search point (CSP)
Where each SRU starts its pattern — shown as a dot at the start of each track.
Sub-areas
With several SRUs the OSC or SMC splits the area so every unit has its own, without gaps or overlaps.
Choose a pattern
Parallel track (PS) — 1 SRU
When to use it
The search object's position is uncertain and the area is large, with the object equally likely anywhere in it.
How it is performed
Long search legs run parallel to the long side (major axis) of the area, usually along the drift, each one track spacing (S) from the last and joined by short cross legs. It gives even coverage of a large rectangle.
With 1 SRU
One SRU covers the whole area alone. It is simple, but slow for a big area.
Safety with several units
The on-scene coordinator gives every SRU its own area or offset, start point, track spacing and radio checks. Units report reaching their start point, each leg, and anything sighted.
Lifeguards and beach rescue
Beach and surf lifeguards use many of the same ideas for a missing swimmer: creeping line, expanding square and parallel line searches, run on foot, by swimmers, on rescue boards or in IRBs. They also use what some organisations call a circle search: one lifeguard stays at or near the last known position (datum) while the others swim concentric circles around them, widening after each lap. Choose "Circle search (lifeguards)" above to see it.
Based on the search patterns in the IAMSAR Manual, Volume II (coordination) and Volume III (mobile facilities). Charts are simplified teaching drawings, not to scale for real planning. Expanding square and sector search are shown with at most two units, as IAMSAR allows. The circle search is a lifeguard practice, not an IAMSAR pattern. For offshore structures see the Offshore SAR Learn page. To see the real rescue boats that run these patterns, browse the SARfleet rescue boat database.