Grid vs. Ground in RTK data collector?
Could be Kent.
All we really know is surveyor B told surveyor A his work was in grid instead of ground. Whatever the heck that's supposed to mean. We can (I believe reasonably) infer that surveyor A couldn't be bothered to actually investigate B's claim, and decided to simply pass it on to the least qualified person within arm's reach in the office.
We don't know what led B to this conclusion nor do we know why it would be a problem needing to be fixed. Given the apparent level of professionalism displayed by A (as accounted to us), I suspect he would just as capably eff up a total station survey. But I would not be surprised to find you are correct. In which case I'd suspect grid v ground is probably the least significant issue in A's work. Of course this is mostly conjecture from limited information.
Newt...
Because of what I stated above it is practically impossible to diagnose and resolve the issue. It's not entirely clear what the issue actually is. And as Norman Oklahoma said, this is the surveyor's job. It's what he does. Essential to his profession.
We discuss the relationship between measurements along projection grids and along the Earth surface quite often here. The topic you present is a good one, worth discussing, but the impetus is horribly wrong.
Right on, Moe.
Keep at it, Harold. You're catching on, but some of what you said is incorrect.
Thanks, guys. Will do. I agree; my post needed correcting and clarification.
My internal magnetic compass was off a little!
Grid vs. Ground in RTK data collector?
> We don't know what led B to this conclusion nor do we know why it would be a problem needing to be fixed.
Well, that part should be fairly easy to figure out. Another surveyor measured a couple of lines and found that it was out of scale by about 250 ppm or more (1:4000). The obvious conclusion is that it was calculated on some map projection while presenting the distances as being surface distances (as one would normally assume without some statement to the contrary).
> ... I suspect he would just as capably eff up a total station survey. But I would not be surprised to find you are correct. In which case I'd suspect grid v ground is probably the least significant issue in A's work. Of course this is mostly conjecture from limited information.
That's the point. One very rarely sees conventional surveys with large errors like that. It's pretty much a feature of RTK work and for the obvious reasons.
James,
The jest of the point was that unless you are aware of how you want to convert to ground the DC is not going to be able to do it for you.
My point was that the data collector will not export ground coordinates automatically from a true geodetic coordinate system. You, the user, must specify the method in which you will bring the ground to grid. In your case you are entering the parameters you would like to use. In the case of localization/site calibration, you are having the DC calculate them based on a set of measurements you determine. No matter what, you have made the decision on how to make the conversion.
The original post implied that if you were working in lets say California Zone 4, you could hit a button that would automatically and magically make these decisions for you. The "Boss" may have seen ground distances in the DC but unless he input the conversion parameters he got grid coordinates upon export.
Now back to the flinging my body down a Mexican highway @ high rates of speed.
Point taken,
watch for goats! 🙂
More like coyotes and buzzards. This is the last day a 3 day race out of Chihuahua. Today is to the a run to the border through the Pegasus canyon.
Trimble data collectors will convert grid to ground. All you do is go into your coordinate system settings and change it, then put in a scale factor. It will also shift and/or truncate the coordinates so they don't look like state plane.
All your distances or plotting will be wrong by an approximate factor of about 1.0003 (roughly based on the mean elevation of Colorado). If you have a tie to a section corner a mile away your distance will be wrong by over 1-½ feet. distances within 100 feet will have insignificant distance differences. However it would be better to apply the appropriate scale factor for your work site. If a follow-up surveyor knows that you are publishing State Plane Coordinates and what datum they are on, that surveyor can probably deal with it accordingly, but they have to know the "metadata" associated with your grid. It sounds like your boss doesn't even know that and wouldn't know how to deal with it himself.
Grid vs. Ground in RTK data collector?
Nah, I bet they probably used the RCG (Random Coordinate Generator) :clap: !
