Patent ID: 7646329

Claim:
A method of detecting a target in a scene, comprising by the steps of: (a) taking a first data set of data elements each of which corresponds to an average of two or more returns obtained at respective times from a part of the scene during a first time period; (b) taking a second data set of data elements each of which corresponds to an average of one or more returns obtained at respective times from a part of the scene during a second time period subsequent to the first; (c) generating a comparison of the value of a data element in the second data set with the value of a data element in the first data set, the data elements corresponding to returns from the same part of the scene; (d) comparing said comparison to a threshold value so as to detect targets entering said same part of scene during the second time period and giving rise to a comparison having a value exceeding the threshold value; and (e) repeating steps (c) and (d) for data elements in the first and second data sets corresponding to returns from other parts of the scene.