Topcon's Millimeter GPS provides measurements within a few millimeters instead of centimeters. This vertical accuracy allows the RTK GPS to perform with the precision of a robotic total station. The system consists of a zone-beam laser transmitter that sweeps a 2,000-foot-diameter area with a 30-foot-high wall of laser light. A compact sensing unit fits over the top of the range pole. When the sensor is positioned within the laser zone, the laser provides vertical data that results in vertical measuring precision to the millimeter. Estimated list price: $12,000 for first unit; $3,000 for additional rover sensor.