A system and method of for estimating the depth of a marker may include a marker locator. The marker locator may include a first transmitter that generates a first activation signal, second transmitter that generates a second activation signal, a receiver that detects first and second response signals, and a processor that determines a depth of a marker based on the first and second response signals. The first transmitter is located at a first position, and the second transmitter is located at a second position apart from the first position. The first and second response signals respectively correspond to the first and second activation signals. The processor is coupled to the receiver. According to some embodiments, the first and second activation signals and the first and second response signals may be separated by time division multiplexing.