Equipment World Digital Magazine
Issue link: http://read.dmtmag.com/i/692436
F or the contractors who invest in them, GPS/ GNSS systems can de- liver huge gains in earth- moving productivity, accuracy and speed. But because these are electronic and digital products, and because full blown GPS/GNSS systems for automated blade control can cost $60,000 to $100,000 per machine, many con- tractors have not taken the leap. If the complexity of these systems has you sitting on the sidelines, or if you just need a refresher in the technology, this series of articles on GPS/GNSS 101 is for you. For our introduction to the basics, we asked David Hilbig, Southwest regional sales manager for construction at Topcon Posi- tioning Systems, to explain how the components of a GPS/GNSS system work together. In future articles we'll go into more depth on how to set up excavators, doz- ers and motor graders with GPS/ GNSS machine control and we'll finish the series talking about how to integrate this technology into a site-wide control system. How does GPS/GNSS work? In simple terms, these systems receive the same satellite position- ing signals you get on your car or smartphone map and navigation systems. The big difference is that systems designed for survey and earthmoving operations receive broadcasted radio corrections from on-site GPS base stations to make it highly accurate for rovers or ma- chines in the field. The rovers use this information to check or survey a site without the need for stakes in the ground. The machines use the information to cut, fill or dig to a profile that exactly matches the X-Y-Z coor- dinates on a digital topographic plan. This eliminates the majority of the survey staking that a site needs and the wait times that often accompany resurveys. An operator in a machine that is GPS/GNSS guided has two op- tions. In the "indicate" mode, he sees the final contours of the site on the digital plan on the screen in his cab and manually adjusts the elevation and slope of the blade to match the plan. In the "automatic" mode, the machine's hydraulics take over the blade and automati- cally make those adjustments. In addition to eliminating most of the staking chores, GPS/GNSS makes less skilled operators more efficient. And it can prevent opera- tors from overcutting a pass and having to move the dirt multiple times to achieve final grade. EquipmentWorld.com | June 2016 25 GPS/GNSS 101 | by Tom Jackson | TJackson@randallreilly.com The basic building block of a GPS/GNSS system Part 1 of a 4-part series The base station receives satellite positioning information, corrects it for accuracy and radios it out to man and machine rovers in the field.