Patent ID: 8210435

Claim:
An apparatus for marking predetermined known overhead positional locations within a coordinate space, for viewing by an image acquisition system, the apparatus comprising: a plurality of marker tags, the marker tags being grouped in one or more rows, each row having an axis, the marker tags in a row group being supported by a row support, each marker tag comprising: an optically opaque, substantially stiff substrate, substantially rectangular in shape, a label positioned centrally on the substrate, each label having a unique machine-readable barcode symbology printed thereon, a border of the substrate surrounding the label; each row support comprising: a first support cord for supporting a first lateral edge of the marker tags in a row group in a fixed, spaced-apart positional arrangement, and a second support cord for supporting the second lateral edge of the marker tags in the row group in a slidable support arrangement, the first support cord being attached to an overhead support structure at each end with a tensioning device, the support cord being drawn to a predetermined tension, thus establishing a substantially straight first lateral row edge, the tensioning devices on the first support cord permitting precise positioning of the marker tag group along the row axis; the second support cord being attached to the support structure at each end with a tensioning device, the support cord being drawn to substantially the same tension as the first support cord, so that the marker tags are supported in a substantially horizontal plane, the slidable support of the second lateral edges allowing the marker tags of a row group to align along the first lateral edges.