Equipment World Digital Magazine
Issue link: http://read.dmtmag.com/i/699963
from a base station set up at the jobsite. Likewise, the operator plugs a digital, 3D topo map of the site into the excavator's monitor and either cuts to the line shown on the monitor (indicate mode) or puts the system into full automation mode and lets the GPS/GNSS positioning data guide the bucket to the exact contours of the design grade. If you already have a GPS/GNSS system running your dozers or excavators, you can use the same base station and radio transmitter to guide your excavators at the same time. The RTK signal is broadcast over a wide area and can be used simultaneously by any number of machines on a jobsite. Benefits With the precise positioning of the bucket's edge made possible through GPS/GNSS excavator sys- tems you get a number of benefits: • No over-digging. The bucket stops at the exact bottom of the trench, so you never disturb (and consequently have to re-compact) the existing soil below grade. Also, you don't have to fill in low spots with fresh material and you don't have to put compaction equipment in the trench or the footings that you dig. Dig once, and move on. • Safety. With the accuracy of the dig controlled by the GPS/GNSS data to a centimeter or two, you don't have to put a rod man down in the trench to measure the depth and you don't need the surveyor above ground calibrating the accu- racy of your work. That reduces the risks of putting people in a trench and frees up two people for other tasks. This is a huge advantage, especially in deeper trenches where you would otherwise be required to use shoring boxes or cut back the sides of the trench – which often involves more digging than the actual trench. • Cut complex contours singlehandedly. With GPS/GNSS guidance, the role of the excavator as the machine that hogs out the dirt before other machines come in and clean up behind it may be coming to an end. Culverts with flat bottoms and sloped sides, pads and mounds, and retaining ponds can all be carved accurately with- out disturbing the underlying soil and without the need for finish or cleanup machines. • Precise slopes for pipelines. Gravity-fed water and sewer sys- tems require extremely accurate downhill slopes over long distanc- es. With the GPS/GNSS guidance an excavator can cut a 3-degree or 5-degree slope (or any number, for that matter) for a pipeline for miles without the need for regular survey- ing and the worry that you may have a high or low spot somewhere along the length of the trench. Availability and brands At present Caterpillar and Komatsu offer factory-installed GPS/GNSS systems on their excavators. But you can also outfit other brands of excavators or older models with aftermarket kits from technology companies such as Topcon, Trimble and Leica. July 2016 | EquipmentWorld.com 50 GPS/GNSS 101 | continued The in-cab monitor on a GPS/GNSS excavator shows the digital design plan and the position of the excavator and bucket in real time.