A spatial relation,J Freeman (1975), "The modelling of spatial relations", Computer Graphics and Image Processing, Elsevier. DOI: 10.1016/S0146-664X(75)80007-4D. M. Mark and M. J. Egenhofer (1994), "Modeling Spatial Relations Between Lines and Regions: Combining Formal Mathematical Models and Human Subjects Testing". PDF specifies how some object is located in space in relation to some reference object. When the reference object is much bigger than the object to locate, the latter is often represented by a point. The reference object is often represented by a bounding box.
In Anatomy it might be the case that a spatial relation is not fully applicable. Thus, the degree of applicability is defined which specifies from 0 till 100% how strongly a spatial relation holds. Often researchers concentrate on defining the applicability function for various spatial relations.
In cognitive development for walk and for catch objects, or Water-level task; in robotic Natural Features Navigation; and many other areas, spatial relations plays a central role.
Commonly used types of spatial relations are: topological, directional and distance relations.
The DE-9IM model expresses important space relations which are invariant to rotation, translation and scaling transformations.
For any two spatial objects a and b, that can be points, lines and/or polygonal areas, there are 9 relations derived from DE-9IM:
More complex modeling schemas can represent an object as a composition of simple sub-objects. Examples: represent in a astronomical map a star by a point and a binary star by two points; represent in geographical map a river with a line, for its river source stream, and with an strip- area, for the rest of the river. These schemas can use the above classes, uniform composition classes ( multi-point, multi-line and multi-area) and heterogeneous composition ( points+ lines as "object of dimension 1", points+ lines+ areas as "object of dimension 2").
Two internal components of a complex object can express (the above) Binary operation between them, and ternary relations, using the whole object as a frame of reference. Some relations can be expressed by an abstract component, such the center of mass of the binary star, or a center line of the river.
Stockdale and PossinC. Stockdale and C. Possin (1998) Spatial Relations and Learning. discusses the many ways in which people with difficulty establishing spatial and temporal relationships can face problems in ordinary situations.