The present invention relates generally to access control. One claim recites a method of determining whether to allow access to a location, including: receiving optical data from an optical sensor, the optical data being associated with an object presented to the optical sensor, wherein the object comprises optically-detectable, machine-readable indicia encoded in a predetermined symbology thereon, the indicia including at least an orientation component; determining an orientation of the orientation component; obtaining from a data store a predetermined orientation; and comparing the predetermined orientation with the determined orientation to decide whether to allow access to the location. Of course, other claims are provided as well.