LSA does NOT give you the most accurate or best solution for any point.
It gives you the most probable and that is based on your input variables.
And that 0.007 mm+1 ppm is actually ?ñ(0.007 mm+1 ppm), not 0.007 mm ?ñ 1 ppm.
I just learned from this here thread that I are ELITE!
where do I pick up my badge?
Really. It is documented in Standards and Specifications for Geodetic Control Networks, published in 1984. It specifies the procedures to achieve various orders of accuracy when triangulating, traversing, and levelling. But it doesn't mention GPS, because GPS was barely a thing then. That specification has been replaced a couple of times over, most recently by the Federal Geographic Data Committee's Geospatial Data Accuracy Standards in various parts. Those standards, themselves 20 years old, dispense with references to orders of survey accuracy entirely. So, yes. That nomenclature is obsolete.
Furthermore, referring to accuracy in terms of loop closure is inappropriate when measuring anything other than a closed loop, and who does that with GPS?
Time spent adjusting is...??.pfffft.
But time spent trapping and correcting blunders is time well spent. The act of running the data through an LS adjustment shows you where the blunders probably are thus facilitating their correction. By the time you have the blunders weeded out you have an adjustment.?ÿ Many times the data has no blunders. In that case I have spent next to no time and I have mathematical proof that my data is (probably) blunder free.
If you are spending a lot of time analysing data that is blunder free you are doing it wrong. If you are accepting data as blunder free without analysis you are letting a lot of bolluxed data out of your office.?ÿ?ÿ
And that 0.007 mm+1 ppm is actually ?ñ(0.007 mm+1 ppm), not 0.007 mm ?ñ 1 ppm.
Substitute m for mm in the above.
In the time that we were arguing over better method, the accuracy has increased to 0.003 m + 0.5 ppm for static accuracy.
In the time that we were arguing over better method, the accuracy has increased to 0.003 m + 0.5 ppm for static accuracy.
That's a 1-sigma value.?ÿ The 2-sigma equivalent (e.g. per ALTA specs) is about 0.007m.
Well, if your story is correct I am glad to hear that the GRX1's specifications finally caught up to the industry's old norm.
I have some old Leica SR530 receivers. In 1999, Leica published the specifications on those GPS-only receivers to be:
Accuracy, baseline rms: Accuracy in position = baseline rms. Accuracy in height = 2 x accuracy in position
Baseline rms with post processing
Static, long lines, long observations, choke-ring antenna: 3mm + 0.5ppm
Static and rapid static with standard antenna: 5mm + 0.5ppm
Yes, I see the stats, but I'm not sure about their interpretation. And it's certainly not essential that I understand, but some other folks might have similar questions.
For example, consider the attached snippet from an NGS datasheet:
Note that the network standard deviations are similar to the ones on your report, but the network accuracy is significantly larger, so we see a difference between positional accuracy and standard deviations.
Going deeper into the network by clicking on the link in the data sheet gives us this for points in the network:
Again, positional accuracy and standard deviation differ by an order of magnitude.
So, what positional accuracy are you getting? is it better than NGS gets? How do you know?
I learned a lot from Larry as well. I have a copy of his class on SurvNet. It was good! I don;t think anyone took up the reigns of the book company after he got sick.
But unfortunately LS will not find a blunder in a GNSS position alone. You would need a traverse run through the point as well in order for LS to indicate you might have had a "bad fix". In the GNSS RTK era we need statistics on each individual occupation showing likelyhood of a "good fix" or not, before running through LS if the LS report is to have any meaning. Unless of course we run a traverse through every point, which defeats the purpose in many RTK instances.
NY is proposing MTS that will require same reporting as ALTA for every survey. So LS not likely to go away soon here.
But unfortunately LS will not find a blunder in a GNSS position alone.?ÿ You would need a traverse run through the point as well in order for LS to indicate you might have had a "bad fix".....
You need redundant measurement but it doesn't have to come by traversing. A 2nd RTK vector to the point taken with some time offset would be minimally sufficient.
Always keeping in mind that these specifications are for factory fresh receivers working on the test bench under laboratory conditions. Real world results vary, always to the worse. And they are for errors caused by the receivers only. It says nothing about centering errors, multipath, etc.
