A method of estimating the position of a radiation blocking object on a surface, the method comprising: - providing a frame having a top side, a bottom side, a left side and a right side; - providing a first radiation sensor on the frame and a second radiation sensor on the frame, wherein the first radiation sensor and the second radiation sensor are separate by a distance; - providing a plurality of radiation sources, wherein: - radiation emitted by at least some of the radiation sources passes across the surface and is incident on the first radiation sensor; and - radiation emitted by at least some of the radiation sources passes across the surface and is incident on the second radiation sensor; - sequentially activating at least some of the radiation sources; - obtaining a first series of radiation intensity levels provided by the first radiation sensor in response to the radiation emitted by at least two radiation sources of the plurality of radiation sources and incident on the first radiation sensor; - obtaining a second series of radiation intensity levels provided by the second radiation sensor in response to the radiation emitted by at least two radiation sources of the plurality of radiation sources and incident on the second radiation sensor; - assembling a first radiation intensity signal from the first series of radiation intensity levels; - assembling a second radiation intensity signal from the second series of radiation intensity levels; - identifying a first set of one or more attenuated radiation intensity levels in the first radiation intensity signal; - estimating a first angle relative to the first radiation sensor corresponding to the first set of one or more attenuated radiation intensity levels, wherein the first angle is based on a weighted average of the respective angles of the radiation sources corresponding to the first set of one or more attenuated radiation intensity levels relative to the position of the first sensor; - identifying a second set of one or more attenuated radiation intensity levels in the second radiation intensity signal; - estimating a second angle relative to the second radiation sensor corresponding to the second set of one or more attenuated radiation intensity levels, wherein the second angle is based on a weighted average of the respective angles of the radiation sources corresponding to the second set of one or more attenuated radiation intensity levels relative to the position of the second sensor; and - estimating the position of the radiation blocking object based upon a distance between the first radiation sensor and the second radiation sensor, the first angle and the second angle. - providing a frame having a top side, a bottom side, a left side and a right side; - providing a first radiation sensor on the frame and a second radiation sensor on the frame, wherein the first radiation sensor and the second radiation sensor are separate by a distance; - providing a plurality of radiation sources, wherein: - radiation emitted by at least some of the radiation sources passes across the surface and is incident on the first radiation sensor; and - radiation emitted by at least some of the radiation sources passes across the surface and is incident on the second radiation sensor; - radiation emitted by at least some of the radiation sources passes across the surface and is incident on the first radiation sensor; and - radiation emitted by at least some of the radiation sources passes across the surface and is incident on the second radiation sensor; - sequentially activating at least some of the radiation sources; - obtaining a first series of radiation intensity levels provided by the first radiation sensor in response to the radiation emitted by at least two radiation sources of the plurality of radiation sources and incident on the first radiation sensor; - obtaining a second series of radiation intensity levels provided by the second radiation sensor in response to the radiation emitted by at least two radiation sources of the plurality of radiation sources and incident on the second radiation sensor; - assembling a first radiation intensity signal from the first series of radiation intensity levels; - assembling a second radiation intensity signal from the second series of radiation intensity levels; - identifying a first set of one or more attenuated radiation intensity levels in the first radiation intensity signal; - estimating a first angle relative to the first radiation sensor corresponding to the first set of one or more attenuated radiation intensity levels, wherein the first angle is based on a weighted average of the respective angles of the radiation sources corresponding to the first set of one or more attenuated radiation intensity levels relative to the position of the first sensor; - identifying a second set of one or more attenuated radiation intensity levels in the second radiation intensity signal; - estimating a second angle relative to the second radiation sensor corresponding to the second set of one or more attenuated radiation intensity levels, wherein the second angle is based on a weighted average of the respective angles of the radiation sources corresponding to the second set of one or more attenuated radiation intensity levels relative to the position of the second sensor; and - estimating the position of the radiation blocking object based upon a