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The visual element Line is needed for searching the archive by the criterion Object trajectory crossing a virtual line Line visual elementis required for searching  recorded video by the Line crossing criterion. This visual element sets a virtual line in the field of view of a video camera; instances of something crossing this line will be found in the archive.

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By default, both directions of motion across the virtual line are taken into account when searching the archive. If you do not need to search in a specific direction, click the Image Added button corresponding to that direction.

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