Maps and/or signs are embedded with plural-bit data in the form of digital watermarks. In one implementation, an apparatus is provided to read two or more digital watermarks embedded within a map. Each of the two or more digital watermarks includes location information for a respective map location. The two or more digital watermarks are embedded through alterations to data representing the map; the alterations are generally imperceptible to a human observer of the map. The apparatus includes: a global positioning system receiver to determine a physical location of said apparatus; an input to receive data corresponding to at least a portion of the respective map area; a processor or electronic processing circuitry to extract the location information from the input data and to correlate the physical location with the extracted location information; and an output to output an indication of a relative correlation between the physical location and watermark location information. Other implementations are provided and claimed as well.