I have always been a bit dubious about some of the measurements I get back when shooting reflector less shots, so many variables like beam spread, the reflectivity of the surface and backlighting conditions.
I had a lot of bad results once shooting the outside diameters of stainless steel wine tanks once, so today I thought I would see if I could fix the position of the lightning conductor rod at the top of a cell phone tower.
I reckon the rod was about 12-16mm in diameter and protruded about 1m above the tower lattice, the rod was copper I presume and very dark. You can just see the lightning rod protruding out of the lattice tower on the left in the photo
I did not think It would shoot...well it was only 119m away from me and 48 m higher than me, but it shot no problem, and i shot right on the tip.
I was impressed. It is the cell tower on the left of the photo...sorry the pic is sideways, it is upright on a mac or iphone, I think it has something to do with the sensors, as I often get complaints of upside down video files from windows users.
Or maybe it because with use a south azimuth system here 😀
Lee
We were doing some deformation monitoring around a construction site a while back in a very confined space. We were not able to establish any permanent stations on the ground so a bunch of tape targets were set on solid walls that we had no concerns about and a bunch were set on the wall of concern.
We'd go in and do a 5+ point resection to establish where we were that day and then shoot to the other targets. The tightness we were able to maintain was amazing.
Equipment was a Topcon 3003.
Prior to starting we ran some tests on my baseline with samples of the tape targets turned at all sorts of crazy angles to the line of sight to make sure we didn't have any issues with the acuteness of the target relative to the sight. Within the bounds of being reasonable, we had no problems.
stainless steel IS NO BUENO for reflectorless or scanning.
We are using reflectorless to locate the post tensioning sleeves of SFO's new Air Traffic Control Tower. So far fairly consistant measurements, so the designers are pleased.
Brad Luken, LS
AZ, CA, NV & OR
I've had "good luck" locating poles hidden behind obstructions by tying the wires going in both directions
Reflectorless hints (slight hijack)
Anything metal is iffy with reflectorless. You may get the shot,or you may get a bad distance. If you are lucky it will be obviously bad, but if you are not lucky...
I carry a roll of drafting tape in the car for use on most surfaces. I've never had a bad distance on tape.
Also very useful are craft sticks (wider than popsicle sticks), sprayed with pink paint for easy visibility. I stick them in the ground for edge of sidewalk shots.
And, wood stakes cut into 1" blocks, also sprayed with pink paint, are great for elevation shots. I set the reflector height at 0.02 feet and shoot just above the bottom.
Reflectorless hints (slight hijack)
> And, wood stakes cut into 1" blocks, also sprayed with pink paint, are great for elevation shots. I set the reflector height at 0.02 feet and shoot just above the bottom.
I needed some reflectorless targets the other day for mapping some points on a driveway and improvised by cutting a piece of the 1/2-inch PVC irrigation pipe that I use for laths into 3/4-inch stubs. They were quick to make and gave a good reflection.
Reflectorless hints (slight hijack)
i find matte metal surfaces perform well at with reflectorless shots. obviously anything with a surface approaching a mirrored finish will reflect less and less of the signal back for processing.
i've lost count of the unexpected reflectorless returns at medium ranges so the one that impressed me the most was a shot to a wooden electricity pole with an R1000 TCRP1205 of 970 m (3182 ft) on an overcast late afternoon.
big hijack & OT: i think i hold the record (as far as i know) of for an ambiguity fixed RTK GPS baseline with a 35W radio of ~94 km. ground truthed it too and it was good.
Reflectorless hints (slight hijack)
I also needed some reflectorless targets on a title survey a few weeks ago. I ended up putting masking tape over the ring of a few chaining pins and drew a target on the tape. I also put a ring of tape on the stem of the pin that was .5' below the target that I drew to keep the elevation dogs at bay.
Ideas like the ones on this thread are really great for sharing. Maybe we should ask for a tips and tricks category on the message board.
Reflectorless hints (slight hijack)
as for target tips then, all you need to do is buy a roll of diamond grade reflective tape and cut out 10mm squares to stick on anything you wish to shoot reflectorless. i can only speak for our leica instruments but a target this size will ensure a reliable signal return from a hundred metres away, at cents per target (if that).
the risk of stray returns from intervening objects, and hence an unreliable distance calculation, seem to go to virtually nil when adding some reliable reflective return according to my tests where i interrupt 80% or more of the beam with an obstruction and the distance is still reliable to within a mm or two.
it appears that as soon as a well reflecting object is in the beam then the instrument will adjust the EDM output power to ensure the correct level of beam return. once the beam is coming back off some amount of reflective tape it is adjusted to such a low power level that it will not return a significant amount off any other objects in in the path of the beam.
our assistants carry small steel rulers with reflective tape stuck to the bottom to use as ground level targets, and i'm to the point now where i consider this to be as reliable, and at least as accurate as a well adjusted prism & pole.
i can't speak well enough of reflective tape targets for prismless work (where the target is accessible of course) and we now buy the stuff off ebay like addicts and use it on projects whenever we can. it is stable, cheap and lasting control when stuck to buildings.
Reflectorless hints (slight hijack)
I used your brick backsight idea once only I used a guard stake. That worked great for what I needed.
Lane stripe reflectors make good targets for shooting centerline on a busy street while staying out of traffic.
Reflectorless hints (slight hijack)
Call me crazy, but if you can physically occupy a topo point why would you shoot it conventionally? It seems that if you are going to the effort of setting up back stops then you might as well shoot it with a reflector.
Reflectorless hints (slight hijack)> Why would you?
solo workers.
I use reflective tape and measure up 6' HI's for the shots.
Reflectorless hints (slight hijack)> Why would you?
> solo workers.
>
> I use reflective tape and measure up 6' HI's for the shots.
Okay, I can see that if your gun is not robotic.
While back had to tie some centerline monuments on an extremly busy section of highway. No way was I going to put a reflector on the monument only to have it run over. Desperately looking around for a disposable target, I spotted my instrument stuffing his face with DOT candies, sort of a cone shaped gummy bear in various colors and flavors. A quick dash between traffic and I was able to place a DOT, pineapple flavor if I recall on the point and dash back to the gun to take a reflectorless shot. In the field notes I wrote 'DOT centerline mon shot reflectorless using DOT candy target, pineapple flavor'.
Just because I'm paranoid, doesn't mean they aren't out to get me.
Reflectorless hints (slight hijack)
I have 6 pins taped up and marked with cross hairs. If it is a large job I will tape up the other 5 in the set and maybe break out the other set. While working by myself I can walk out and set the pins, take the shots and pick up the pins, giving me six shots. It saves me many steps. I only have two prisms. I shoot in the property corners with prisms but when it comes to the side walks and driveways etc, I can make quick work and save a little bit of walking. I guess it is just personal preference.