| 摘要 |
PROBLEM TO BE SOLVED: To prevent a target from being lost even if the target suddenly changes (detours) a course when encountering with a water region such as lakes and marshes or the like, or a cliff edge. SOLUTION: An estimate judge part 7 judges with reference to information on an unreachable region enlarged more than a water region such as rivers, lakes and marshes or the like within a monitor section which is provided from an unreachable region-enlarging part 6b whether a next reach estimate position of a target calculated at present is within the enlarged unreachable region or not. As a result, if the next reach estimate position of the target is judged to be within the enlarged unreachable region, a track file 9 does not update an already registered estimate position at the (unreachable) next reach estimate position calculated at present. Instead, a correlation process part 3 enlarges a correlation gate when carrying out a correlation process at a next time.
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