1. A method of identifying an object, comprising: detecting in an image repeating reference forms and a set of elements, said set of elements at a pre-defined distance from and orientation to said repeating reference forms; wherein upon occlusion of at least a part of a first of said repeating reference forms and set of elements, said detecting comprises detecting in said image a second of said repeating reference forms and set of elements; deriving a value associated with said second set of elements; and comparing said value to a value stored in a memory, where said value stored in said memory is associated with said object.