Topcon and TSD Integrated Systems, a joint venture with Sauer Danfoss, applied Millimeter GPS technology to paving applications with its new AutoPave product. The company claims AutoPave will provide grade-control accuracy equal to a robotic total station at lower cost and increased flexibility like a rotating laser.
Robotic total stations — whose lasers lock on and track receivers mounted on pavers — have pioneered automated, stringless grade control in paving. Global positioning systems (GPS) alone lack the precision in vertical measurements to deliver precise grade control necessary for pavers to pass profilograph tests.
Topcon's Millimeter GPS system overcomes vertical-plane limitations by augmenting GPS' excellent horizontal positioning with what they call the Lazer Zone. The Lazer Zone generates vertical accuracy to within a few millimeters, compared to the centimeter vertical accuracy of conventional real-time-kinematic GPS.
On pavers, Millimeter GPS is achieved with Topcon's zone-beam laser transmitter. The PZL 1 emits a patented 'fan beam' signal with a height of 10 meters (about 33 feet). It sweeps a 2,000-foot-diameter area with this 33-foot-high wall of laser light.
A sensor, the PZS MC, is mounted on a mast attached to the toe arm of the paver. Any time the PZS-MC sensor is positioned within the laser zone signal, the system provides vertical data resulting in millimeter precision. The laser's 33-foot field of view makes it easier to keep the sensor in contact with the guiding signal.
Up to four PZL-1 transmitters can be linked together increasing the vertical working area to 133 feet or 7,880 feet horizontally. Rovers move from one transmitter to the next seamlessly.
Because the PZL-1 is a rotating laser, not master/slave dedicated to the paver like a robotic total station, multiple Topcon rovers (integrated to anything from 3D grade-control systems to grade-checking poles) can work with millimeter accuracy from the same laser.
AutoPave is the top end of TSD's new family of automated paving control systems. It is expected to cost a little more than half of the cost of 3D paver controls using robotic total stations. The other two TSD systems include the economical ReadyPave and MasterPave, with TSD's Quattro four-headed sonic sensor.