UAS Search Patterns

Air searches are not a new concept - and they certainly are not exclusive to unmanned aircraft. Organizations such as the Civil Air Patrol and the US Coast Guard have spent decades developing and refining techniques for conducting air searches. These methods have been used successfully all over the world, but are intended for manned aircraft operating over large areas and at altitudes above the typical small UAS flight. CDRP has developed modified search patterns and profiles that are based on proven techniques, but are adapted for the small UAS to utilize.

These UAS Search Patterns are appropriate for searches for persons or material/objects (providing it is large enough to be detected). They should be utilized as part of a search strategy - all searches are more effective when all available resources are working together in a coordinated way.

Search Methods and/or Patterns

These search methods utilizing sUAS are guidelines - not hard and fast templates. The search manager and sUAS RPIC should collaborate on the effective usage of sUAS in the overall search effort, keeping in mind the strengths and weaknesses of the sUAS platforms and crews.

Hasty Search

The Hasty Search is a amalgam of a variety of search tactics that are targeted at specific likely locations of the subject. The Hasty Search sounds unorganized, but the term comes from the fact that it is typically conducted first, with resources that are available immediately.

In the application of sUAS in search, the Hasty Search tactic may include variety of searches that typically have a few common factors:

• The sortie is a live search.
• The sortie is flown manually - no automated flight plans or search patterns.
• The sortie is targeted by a search manager or team leader. "Go check that waterline, then all the stands of trees in the Division area." or "Check the bottom of the cliffs in Division B."

Hasty Searches (on the ground or in the air) are often effective, and should be directed at areas where there is a high chance of immediate success; the so-called low hanging fruit. In many scenarios, sUAS can search areas faster and safer than ground based searches, such as elevated structures, swift-water areas, ravines, and other areas that would require high-angle technical rescue. In cases where a child or at-risk adult has wandered or eloped, a Hasty Search should be conducted in the immediate vicinity of the subject's home, residence or care facility.

Effective Use Scenarios: Unstructured initial searches of areas the subject is likely to be. Locations or areas where the sUAS can reach faster or safer than ground based search resources. 

Flight Altitude or Profile: Altitude AGL varies - often flown very low, very close to obstacles and structures. sUAS crew should be mindful of regulations and risk to persons on the ground.

Planning the Hasty Search: While the Hasty Search does not typically involve automated pre-planned flight, the sortie or sorties should be carefully planned with the search manager or search team leader. Experience, practice and intuition are important to selecting appropriate search targets and areas for immediate resources to cover. By operating under the direction of the search manager, the sUAS resource avoids duplication of effort and minimizes the risk of missing areas. 

The aircraft should be operated at appropriate altitudes and distances to structures, terrain features and obstacles. Sensors appropriate for the target, conditions, and other factors should be employed.

Products of the Hasty Search: The main product of the Hasty is the initial, rapid, live search. In the event that a target is identified, the product delivered to the search manager should be the location or coordinates of the target as well as possible a photo or other supporting information. Coordinates should be in a format pre-identified with the search manager, search team leader, or planning section. Video recording, with positional information if available, should be made of the sortie, and should be examined when time permits. 

Integration of the Hasty Search:  The ad-hoc nature of the sUAS Hasty Search makes it relatively easy to integrate into other search resources' workflows. An embedded sUAS team can perform hasty search sorties as part of a ground search effort, supporting other search resources. For examples, a ground team working an area with elevated structures or ravines could utilize an embedded sUAS to conduct hasty searches of terrain or features that would otherwise be difficult or unsafe to reach.

Parallel Track Search

The Parallel Track Search is the basic grid search - the sUAS is flown in a series of parallel 'tracks' or 'legs' covering an entire designated search area. sUAS Operators often refer to the Parallel Track Search as 'mowing the lawn' due to the resemblance of the search pattern to the path taken to mow the grass.

The Parallel Track Search can be used to cover a large or small area, but it typically best on relatively flat terrain focused on the subject's last known point (LKP) or other datum. The search pattern requires post flight analysis of the captured imagery to increase effectiveness and generate the highest possible probability of detection (POD.

This pattern is often employed by sUAS operators because it is the default pattern used by commercial mapping software. These software programs will automatically generate a flight path appropriate for capturing nadir images used to construct ortho-mosaic photos or other photogrammetry products.

Effective Use Scenarios:  The Parallel Track Search is a deliberate, programmed flight pattern. It is best employed on flat or level terrain where tree cover is broken enough to allow sensors to see the ground. No sUAS sensors (with the possible exception of LIDAR) permit view through tree canopy and other overhead obstructions.

Flight Altitude or Profile: Flight altitude is determined by a variety of factors, including: sensor sweep width, desired POD, desired sweep overlap or sidelap, and terrain and other obstacles.

Sensor sweep width is a variable of camera or sensor angle of view (AOV) and altitude. The higher the UA operates, the wider sweep width; the lower the altitude, the narrower the sweep. At the same time, the higher the UA (and therefore the wider sweep width) the resolution or Ground Sample Distance is reduced. To gain more detail, the UA must be flown lower, while reducing sweep width of a single track, and resulting in higher flight times. This simple trade-off is the heart of the search problem using sUAS. 

Planning the Parallel Track Search: 

Products of the Parallel Track Search:

Integration of the Parallel Track Search: