The 3-space is in differential motion
, that is one part has a velocity relative to other parts, and so involves a velocity field v(r, t) description.
Because the key to reducing whiplash injury risk in rear-end crashes is to keep an occupant's head and torso moving together, the redesigned seats and head restraints are intended to reduce the differential motion
of the head and torso.
"What we are preventing is a differential motion
-- the head moving relative to the chest," Locke explains.
The range of the differential motion
vector can be selected on a picture-by-picture basis, to match the spatial resolution, the temporal resolution and the nature of the motion in a particular sequence--the maximal allowable range has been chosen large enough to accommodate even the most demanding situations.
"If differential motion
is occurring and you constantly monitor coordinates of established benchmarks, you can see it in real time [with the- satellites].