title: Speed and accuracy of head- and eye-based aiming systems at high vertical acceleration.
abstract: BACKGROUND
  The benefits of using a head tracker in a fast jet to aim weapons and control sensor direction have been amply demonstrated, but head direction is difficult to control at high G. An experiment was conducted to assess whether aiming using the eye, rather than the head, might be advantageous.
  
  
  METHODS
  A centrifuge provided sustained accelerations of up to 8 Gz. Participating aircrew were asked to point at static targets using head- or eye-aiming, maintain the acquisition while the target was lit, and then transfer to the next target as quickly as possible. A helmet-mounted scene camera recorded the subject's view of the target board. A laser mounted by the scene camera was used for head-aiming and to determine head direction. The eye tracker camera and illuminator were also helmet-mounted. The eye and scene images were recorded and analyzed off-line.
  
  
  RESULTS
  Eye-aiming acquisition times and accuracy were affected only slightly by Gz; however, both head-aiming speed and accuracy deteriorated as Gz increased. Eye-aiming was substantially faster than head-aiming at all Gz levels, but head-aiming was more accurate under these experimental conditions. Subjective ratings supported the objective data. A majority of subjects preferred eye to head as an aiming mechanism.
  
  
  CONCLUSIONS
  Eye-aiming was faster and easier to use than head-aiming at all Gz levels, and particularly at high Gz.
authors.affiliation: Crew and Decision Systems, QinetiQ, Farnborough, Hampshire, UK. jineson@QinetiQ.com
authors.forename: Judith
authors.initials: J
authors.lastname: Ineson
authors.forename: Laurence
authors.initials: L
authors.lastname: Durnell
authors.forename: J Louise
authors.initials: JL
authors.lastname: Ebbage
authors.forename: Don N
authors.initials: DN
authors.lastname: Jarrett
authors.forename: Catherine
authors.initials: C
authors.lastname: Neary
authors.forename: Mark A
authors.initials: MA
authors.lastname: Reed
mesh_terms: D000054:Acceleration; D000337:Aerospace Medicine; D005133:Eye Movements / Q000502:physiology*; D005135:Eye Protective Devices; D005260:Female; D019416:Head Movements / Q000502:physiology*; D006260:Head Protective Devices; D006801:Humans; D018471:Hypergravity; D007091:Image Processing, Computer-Assisted; D008297:Male; D011930:Reaction Time