Not to hijack the thread below, has anyone done an analysis as to whether robotics are more or less sensitive to heat shimmer?
Common sense seems to dictate that they would be roughly equal, but I wonder if the EDM frequencies used propagate through the heat shimmer the same as the visible spectrum?
I have only done a little work with robotics where heat shimmer was a concern, and using averaged observations and wrapping more angles seems to mitigate a lot of the problem - but increasing the N size should pretty much always have that effect.
Has anyone read anything scholarly or have pertinent anecdotal evidence on the subject?
I have not had any problems but from your question I must assume that you are robo traversing with legs in excess of 600ft.
Just make sure to stay on top of your guns atmospheric correction factors. The convective refraction we experience in the visible spectrum effects the ~620nm laser minutely.
It gives my VX hell! We were doing a project and I was back at the gun and watched what it did and how much it "tracked" a stable target due to shimmer. That distance was 500' and it was in the summer across a field.
It's a 1" robot and 500' was pushing the limits of what I felt acceptable for that project anyway, so I backed up and worked it from another method.
FWIW, we were staking a sewer line that had a GRAND TOTAL of 0.1% of fall so verticals were VERY critical.
I found that my Trimble 5603 performed well in heavy heat shimmer. Repeated angles and distances well. Measurements compared well with measurements made at cooler times. I don't have any quantitative data to prove it, just my experience.
I don't know, but I suppose that these things operate at frequencies that are not effected as much as visible light is.
May I ask why this question is coming up on November 17th and not July 17th?
> May I ask why this question is coming up on November 17th and not July 17th?
Because that's how my brain works. 🙂
And the other thread about heat shimmer made me think of it...
500' is way outside the box. At 250'-300' confidence tapers dramatically.Treat it like the bench run it is. You are setting random elev on a hub at each offset pair right? And remember to set your next traverse point before staking.
no kidding. that's why I did what I did.
In my experience for single shots they seem worse. You can sample the sight with your eye for longer to get a better idea of where the target is.
However, in averaging mode, they seem better than the eye obviously. When I'm reading longer lines It would not be uncommon for me to set the TS to average 20 shots or more.
I recall reading a paper where light ray bending was estimated by measuring the offset between 2 different emitted colors received at a detector, much like GPS estimates atmospheric effects by sending out a couple of frequencies and measuring the delay. I have no idea when to expect it in a total station however.
Heat waves in the fall can be just as bad as in the summer. Hot pavement and cold air...
The heat waves that you are seeing is refraction, or the bending of light. It affects any optical or laser measurement.
You are not getting a true straight line measurement.
Robotics are also prone to horizontal deflection if the sight line passes very close to a vertical surface. I've had it on a number of occxasions, especially when setting out for new equipment within an existing plant building.
They had a great deal of difficulty when constructing the Channel Tunnel (England-France) until they swapped the survey stations over to alternate from side to side within the tunnel, instead of going down one wall.
Robotics are indeed very susceptible to this effect, for the same reason you can take a twig on line far enough out of focus as to be invisible.
I never meant to question whether or not robotics were susceptible to refraction, but whether or not the effect is greater or lesser (or different in any way) within the range of frequencies that an EDM operates as opposed to the visible spectrum.
