METHOD OF INDEXING ENTITIES

The invention is concerned with a method of building an index to a plurality of entities, where each entity is represented by a point defined in a space. The method comprises the steps of: i) identifying entities whose points are furthest apart; ii) creating a first area, the extremities of which first area are given by the points representing the identified entities; iii) assigning entities falling within the first area to a storage area corresponding to the first area; iv) dividing the first area into a plurality of second areas; v) for each of the plurality of second areas: a) linking each of the second areas to the first area, and b) repeating steps (i) - (v) until the first area includes a single point; and vi) writing the storage areas corresponding to each of the first areas to the index.