What are different search patterns as per IAMSAR ?

PARALLEL TRACK SEARCH (PS)

• Used to search a large area when survivor location is uncertain.
• Most effective over water or flat terrain.
• Usually used when a large search area must be divided into sub-areas for assignment to individual search facilities on-scene at the same time.
• The commence search point is in one corner of the sub-area, one-half track space inside the rectangle from each of the two sides forming the corner.
• Search legs are parallel to each other and to the long sides of the sub-area.

Multiple vessels may be used as shown:

• Parallel track search: for use by two ships.
• Parallel track search: for use by three ships.
• Parallel track search: for use by four ships.
• Parallel track search: for use by five or more ships.