IAMSAR Search Patterns

Search patterns

  • It may be advisable for vessels, especially when searching for a person in the water with either an expanding square search (SS) or a sector search (VS), to use dead reckoning (DR) navigation rather than more accurate navigational methods.

  • DR navigation will minimize pattern distortion relative to the search object since it will automatically account for the currents affecting the search object’s drift during the search. For both vessels and aircraft, if a smoke float or other highly visible, expendable object is available, it should be deployed at a datum and the pattern should be performed relative to it.

  • Precise search pattern navigation using high-precision methods such as global satellite navigation systems will produce good patterns relative to the ocean bottom, but not relative to the drifting search object. This could allow the search object to drift out of the search area before the search facility arrives in that vicinity.

1. Expanding square search (SS) -

2. Sector search (VS) -

3. Track line search (TS) -

4. Parallel track search (PS) -

5. Contour search (OS) -

6. Coordinated vessel–aircraft search pattern -


Expanding square search (SS) -