How does GPS/GNSS work?

In simple terms, these systems receive the same satellite positioning 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 machines 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 coordinates 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 options. 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 automatically make those adjustments.

In addition to eliminating most of the staking chores, GPS/GNSS makes less skilled operators more efficient. And it can prevent operators from overcutting a pass and having to move the dirt multiple times to achieve final grade.