A High-Performance, High-Accuracy RTK GPS Machine Guiadance System

As technology matures, Real Time Kinematic (RTK) global positioning system (GPS) receivers are providing increased performance in accuracy, on-the-fly (OTF) initialization times, measurement speed, and latency. Leica's Dozer 2000 machine guidance system combines an MC1000 GPS sensor, graphic intensive guidance software, a digital terrain model, and a digital site plan. Figure 1 shows the operator's view of the system. The end results is a highly accurate, extremely responsive local navigation system. Engineers can easily upload design information onto a touch-screen machine guidance personal computer (PC) and greatly reduce earthmoving costs while simultaneously recording "as-built" inspection data. The Leica MC1000 machine control sensor is a true 10-Hz, centimeter-level-accuracy, open-architecture GPS sensor specifically designed for machine guidance and control. At the heart of the MC1000's performance are a very stable oven-controlled oscillator (3 x 10(-11)/s short-term stability), a low-power Intel 486-DX4-80 processor, and four user-configurable input/output (I7O) ports. Special algorithms mitigate the effects of multipath and Selective Availability (SA) while providing centimeter accuracy up to 10 times per second with only 30 milliseconds' latency. The high update rate and low latency are essential for machine guidance and control. The MC1000 GPS reference station is capable of outputting RTK and Differential GPS (DGPS) data simultaneously, providing and entire site with GPS information for machine guidance and control, tracking and dispatching of vehicles, and support of survey crews. This article describes how recent advances in technology have combined to produce the Leica Dozer 2000 - a machine guidance system that is ideal for a wide range of earthmoving and inspection applications. (c) 2000 John Wiley & Sons, Inc.