This International Standard defines a method to describe the geometry of a feature that moves as a rigid body. Such movement has the following characteristics. a) The feature moves within any domain composed of spatial objects as specified in ISO 19107. b) The feature may move along a planned route@ but it may deviate from the planned route. c) Motion may be influenced by physical forces@ such as orbital@ gravitational@ or inertial forces. d) Motion of a feature may influence or be influenced by other features@ for example: 1) The moving feature might follow a predefined route (e.g. road)@ perhaps part of a network@ and might change routes at known points (e.g. bus stops@ waypoints). 2) Two or more moving features may be ??pulled?? together or pushed apart (e.g. an airplane will be refuelled during flight@ a predator detects and tracks a prey@ refugee groups join forces). 3) Two or more moving features may be constrained to maintain a given spatial relationship for some period (e.g. tractor and trailer@ convoy). This International Standard does not address other types of change to the feature. Examples of changes that are not adressed include the following: ? The deformation of features. ? The succession of either features or their associations. ? The change of non-spatial attributes of features. ? The feature??s geometric representation cannot be embedded in a geometric complex that contains the geometric representations of other features@ since this would require the other features?? representations to be updated as the feature moves. Because this International Standard is concerned with the geometric description of feature movement@ it does not specify a mechanism for describing feature motion in terms of geographic identifiers. This is done@ in part@ in ISO 19133.