1. A marker detectable by visual means comprising; a. a polygonal border comprising of at least four non collinear salient points, b. a binary digital code on said marker, c. the binary digital code comprising information data, checksum and error correction, d. a first level of binary code readable at a first given distance, e. a second level of binary code readable at a second given distance, f. where said second given distance is less than said first given distance and g. where said second level binary code is smaller in size than the first level binary code and does not interfere with the reading of said first level binary code.