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 digital code readable at a first given distance; e. a second level of binary digital 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 digital code is smaller in size than the first level binary digital code and does not interfere with the reading of said first level binary digital code.