The last two day’s I’ve posted photos looking down on a bulldozer cutting a trail down an escarpment in western Libya. Today’s photo is of surveying the escarpment looking up from the bottom. I won’t post the surveyor’s name to protect the innocent. (I don’t recall where the bulldozed trail was relative to this image, save to say it wasn’t not here.)
At the top of the cliff in the center of the image is a small black dot. That’s the surveyors offsider holding the target. The white speck to the right of the offsider is his Land Rover which perhaps gives some idea as to the scale and height of the escarpment here.
When I started in the industry in 1986 our surveyors were using Wild T1 and T3 Theodolites to set the lines. They’d lay out a sequence of ranging poles on the required bearing and a chain crew would set off to set the station pegs in the ground, often at 50m intervals, sometimes less. Then, using the theodolite and a staff they’d check and record the actual location of the peg.
I recall one day in 1986, I was playing the offsider role when my surveyor kept muttering to himself that something was wrong. Having started off fine, each peg was suddenly about 10cm short from where it should have been. We went out to find the chain crew several kilometers ahead to learn that the chain had broken and they’d tied it together again, making it 10cm shorter in the process! We got little done that day. The chain crew had to retrace their steps and pick up about 7 km of pegs, back to where the chain had broken, and have a do-over the following day with a new chain.
I can tell from the orange block on the tripod legs that the surveyor here has a Wild Distomat, possibly a DI4L or DI5, to give him the distance at the push of a button. He still had to work out his angles but the laser distance measure eliminated the old 4 meter staffs they used to carry around.