If the instruments Adjust for Earth Curvature / Refraction, should the data collector also be toggle to Adjust for Earth Curvature / Refraction.
I would not think so. You would probably get a "double adjustment".
When I was a gunner and DC operator I was told just to tell the rodman when he/she was putting my line of sight next to the edge of something and to move away a little.
When we had a robot and I was left to baby-sit the gun, I made a point to take hold of the controls and focus out to the target and then all the way back in to see if anything was in the way. Crap like leaves in a breeze, tops of weeds, or chain-link fence wires.
That's my .02 quid.
E
Negative, Once Is Enough.
Paul in PA
Test it on a long shot w instrument C & R on, and then w it off.
My guess, based on the one time I did this; the elevation will be the same.
Let us know.
Stephen
> If the instruments Adjust for Earth Curvature / Refraction, should the data collector also be toggle to Adjust for Earth Curvature / Refraction.
Yes, Yes, Yes.
Have had this conversation too many times to count.
Ask yourself this question. "When does my instrument adjust for C&R?"
Every instrument I have ever seen makes the adjustment when they give you processed information. If your data collector collects flat distance and vertical different, then you maybe do not need the C&R on. But who has a dc that gathers that? I've only ever seen one.
All the other dc's gather slope distance and vertical angle. There is no correction applied at that time. The correction gets applied when you convert those raw measurements into processed data (flat distance, vertical difference or coordinates generated from those items).
So this begs the question, if I have C&R on in my dc should I turn it off in my CAD software?
Again, ask yourself, "When is the adjustment applied?". When you process raw data into flat distance and vertical difference. There is no chance you will double apply the correction because you never convert that data more than once.
Turn it on, keep it on, and worry not about double corrections.
Larry P
Thanks Larry, this is similar to what I was told several years ago and now remember after reading your post. Your explanation was more understandable.
WOW!
This is getting VERY interesting...
WOW!
?!?!?
Stephen
In my opinion, when the instrument reads, it provides raw data. When the dc receives data, it is in raw form. It is just right and logical to apply correction to derived/dependent quantities only like the coordinates. When ts is set with cr "on", it always feed the data collection system (onboard or external) raw information. It is always the job of the system to apply correction during computation of derived values.
Larry is correct. It applies to the raw data every time. The only time the instrument applies C&R is while DISPLAYING horizontal and vertical distances. The instrument does not transmit horizontal and vertical distances though, it transmits the raw HA ZA and SD, which are uncorrected.
YIKES. Not a big deal to horizontal work in most cases, but probably helps explain why people struggle to get good vertical results from TS surveys.
?!?! what?
The data collector will apply the corrections to coordinate values won't it? Until lately those coordinate values were the only information I used from the data collector and never had any vertical problems of consequence when C/R was on in the data collector. I agree it did not seem to matter in the TS.
> ?!?! what?
>
> The data collector will apply the corrections to coordinate values won't it? Until lately those coordinate values were the only information I used from the data collector and never had any vertical problems of consequence when C/R was on in the data collector. I agree it did not seem to matter in the TS.
Now, when you say ... "those coordinate values were the only information I used from the data collector " ... are you saying that you just dumped coordinates from your DC into the office computer and did your calculations and map drawing?
If so, when did you:
1. Check to insure accuracy of the data gathered?
2. Adjust the data so that your error was not all left in one place?
Larry P
> Larry is correct. It applies to the raw data every time. The only time the instrument applies C&R is while DISPLAYING horizontal and vertical distances. The instrument does not transmit horizontal and vertical distances though, it transmits the raw HA ZA and SD, which are uncorrected.
>
> YIKES. Not a big deal to horizontal work in most cases, but probably helps explain why people struggle to get good vertical results from TS surveys.
Yep, this is right. Keep C&R turned on in the DC. Prism offsets are different, though. You would not want both the TS and the DC making prism constant corrections.
:good:
These questions would be asked less if the manufactures (both the instrument manufactures and the data collector manufactures) did a better job of explain this in their manuals. I have had the opportunity of learning several different instruments over my career (Sokkia "SETS" in the late 80's, Leica robotic in the middle 90's, Trimble 5600 in the early 2000's, and Trimble s6 in 2005) and data collector's being tds onboard, and handheld, Trimble survey controller, and geodometer onboard, Carlson. None of these products did a good job of discussing what data was applied and when (curvature/refraction, prism constant...) (Please correct me if the manuals have changed in the last 7 years). I always liked the hands on approach and testing first to prove what answer I was getting when using an unfamiliar instrument. I must admit that if I did something out of the ordinary I would always wonder if the answer was correct and would do a quick onsite evaluation to whether it mattered or not. Whereas if the manufacture would have addressed it in a user friendly manual my testing would just prove what the manual said and I would have much better "feeling" of the out of ordinary measurements.
Another correction that has not been addressed is when an instrument wonders out of level and it compensates the tilt by changing the horizontal angle as the vertical angle is turned. That confuses the heck out of me when I have a third party data collector hooked to an instrument during stake out. This may not of been noticed by a lot of surveyors because it takes a lot of vertical angle change to show up horizontally but when doing structural steel layout or work with a lot of vertical change, it does make a difference when connected to a third party data collector.
This is a good discussion because there is a whole new generation of surveyors that don't have a standardized tape in the rig and if they do they probably have never been taught to use it correctly to "truth" their instrument, so how do they know the truth! They don't, a lot are running on faith, I guess. Jp
P.S. what about robotic instruments that are not looking at the center of the target but are recording the correct angle??????
