I’ve wondered how the Kiewit workers know when to stop digging. And, how to be sure that the bottom of this four acre hole is flat such that one part of the bus box hole isn’t 25 feet deep when another part that looks to be the same depth, but is only 24 feet deep. I wondered about these things until I saw this…
and this…
The man in the first photo recently walked around the bottom of the bus box hole for 30 minutes or so, stopped every few feet, planted the Frisbee-topped stick on the ground, and appeared to take a reading of some sort. Then I noticed identical looking Frisbees mounted on each side the bulldozer blade, “Hmm, I think I’m on to something.”
You guessed it. Of course, the Frisbees are GPS units that measure elevation. The bulldozer operator knows at all times how deep the hole is. Now I wonder how they did these things way back in the old days, like ten years ago.
Please see our Denver Union Station page at JobSiteVistor.com for photos that are added multiple times a week.
Those GPS survey units are pretty handy. They are manufactured by a company called Trimble <>. They are likely tied into “project space” in real time via a few GPS base units operating at surveyed locations around the site. I think the two receivers on the dozer blade connect to a display in the cab that tells the operator EXACTLY where the blade is and whether to cut. Pretty radical stuff!
I am an engineering geologist, and I have used such portable units to monitor for potential movements over time on active landslides.
Remember, the correct field terminology (at least with a Kiewit crew I had the pleasure to work with) is “Martian Sticks.”
Thanks for your blog.
In the old days they might have used a water level, a tube that when bent in a U will result in the exact same water level on either end.