Getting the most from GPS technology on diggers
Back when GPS kits were first being bolted on to diggers, we were all told how great it was going to be for trimming batters. This new technology was going to do away with manual methods like batter rails and, as a result, cut the cost of batter trimming (which had always been relatively high). The system was also meant to be so effective that we’d hardly even notice work was going on. Maybe it was meant to be so fast it would become one of those things that ‘just happened’ – and we could even leave the cost of batter trimming out of bids. Fast forward 15 years and the cost of batter trimming is still very high and the time taken to complete the task is inordinately long. We didn’t exactly see the hoped-for revolution! The reason for this is simple: we now spend far too much time on batter presentation.
Matching GPS tech to the right stage
Thirty years ago, batters in excavations were cut by the production fleet. There may have been a tidy-up at the end of the job to knock out any points that were clearly out of alignment, but that was essentially it. Fifteen years ago, we still cut the face, but then we’d trim it to make it look a little tidier, and maybe remove some material that could fall out after the construction team had left. Today, we cut the batter, then trim it, and then we polish it. The problem here is that GPS technology is being used at each stage (including the polishing stage) with little recognition of what the following team has planned. Too often, operators are working to the tolerance they think might be right, instead of the tolerance the management team knows is right.
If you want to save money getting batters in an excavation correct, you need to use a GPS on the trimming stage to ensure the final works sit inside the allowable tolerances. Using a GPS to ensure that every square meter of a face is within 10mm of a design plane – ie the polishing stage – is just wasting time and energy.
Project planning tips
For your project planning, I recommend the following basic steps:
Agree on what the final target plane will be. If you are short of fill, consider targeting the low side of the tolerance allowance.
Agree on the target plane for the bulk excavation crew and monitor their performance. Don’t let diggers trim while trucks are waiting!
Consider whether you can use a GPS digger to trim ‘slots’ that are approximately 4m apart. Then let the non-GPS diggers (ie the cheaper units) trim out the material between these finished slots.
Applying the benefits of GPS technology to the right stages in the process will deliver greater value and save on the time and cost burden that comes when you over-work a site.
