Patent ID: 8246164

Claim:
A method comprising: initially moving a handheld device over a print medium, wherein the handheld device comprises a print head and a sensor; while the handheld device is being initially moved over the print medium, having the handheld device deposit, in a tagging pattern, a tagging substance on the print medium; further moving the handheld device over the print medium; while further moving the handheld device over the print medium, sensing, by the sensor, at least part of the tagging pattern, wherein the sensor is disposed adjacent to a top area of the print head such that while the handheld device is being further moved over the print medium, the sensor moves over the tagging substance that was deposited on the print medium while the handheld device was being initially moved over the print medium; determining, based upon the sensor sensing at least part of the tagging pattern as the sensor moves over the tagging substance, at least one of a position and a velocity of the handheld device; and while the handheld device is being further moved over the print medium, having the handheld device further deposit both (i) a printing substance, and (ii) the tagging substance on the print medium, wherein the printing substance is deposited on the print medium based on the at least one of the determined position and the determined velocity of the handheld device.