4.4 The JDL Model

The first attempts at formalising the discipline of data fusion were made in the military domain of command, control, communications and intelligence or C ³I. These efforts date back to the late seventies and early eighties. The early papers ^[4]; ^[5], refer to hierarchical structures, fusion system architectures and adaptive hypothesis testing, all integral parts of modern fusion systems. A major step forward was made in 1990 when the North American Joint Directors of Laboratories (JDL) were charged, through their Data Fusion Subpanel (DFS), to establish a standard data fusion terminology and formulate a coherent strategy for exchanging technical information relating to fusion ^[6]; ^[7]. The standard was augmented in ^[8] by making detection one of the objectives of fusion. The definition of data fusion arrived at was:

"A multilevel, multifaceted process dealing with the automatic detection, association, correlation, estimation and combination of data from single and multiple sources."

The structure of the proposed data fusion model is summarised diagrammatically in Fig. 4.6. It was a hierarchical system of four (or five including pre-processing) levels as follows [ ^[1]]:

• Level 1 Achieve refined position and identity estimates by fusing individual sensor position and identity estimates.

• Level 2 Assist in complete and timely hostile or friendly military situation assessment.

• Level 3 Assist in complete and timely force threat assessment.

• Level 4 Achieve improved results by continuously refining estimates and assessments, evaluating the need...