Have any of you done some basic statistical analysis of observations of your GNSS or total station instruments to prepare accuracy statements for your filed survey maps or other survey products?
If so, would you be willing to share your procedure and statement with me?
I'd like to do this for my own practice, and I'm also thinking about writing an article on the process.
Here is the type of statement I'm talking about:
This survey was conducted with GNSS and total station surveying methods. The instruments used were a Trimble R8 GNSS Receiver and a Trimble S6 Robotic Total Station. Based on the results of field tests we expect the horizontal precision of points (including line end points) shown on this survey are within 0.08 US Survey feet at the 95% confidence level. Based on the results of field tests we expect the vertical precision of points on this survey are within 0.15 US Survey feet.
Thanks.
Landon
Why put a statement on it unless it is absolutely required?
Do you have a calibrated baseline in the vicinity.
Shouldn't you do the precision testing to weight your observations, then report the accuracy of your survey based on the results of your least squares adjustment? I think you will find the errors far exceed just the expected uncertainty of any one measurement. The ALTA accuracy standards spell out a pretty good method and a reasonable standard, I think.
I've been processing data for a good bit of the last 35 years. These last few I've been forced to realize that few people will pay me to do what I do. We are so far removed from the thought processes of error budget, redundancy and error analysis it isn't even funny. I wish you good fortune in resurrecting these wonderful relics...
> Have any of you done some basic statistical analysis of observations of your GNSS or total station instruments to prepare accuracy statements for your filed survey maps or other survey products?
Isn't a least squares analysis of an observation network just that? If so, yes, I do it for every job. The data from an LS adjustment report would allow you to prepare a statement of the sort you are contemplating.
Accuracy Statements about the Geoid are DANGEROUS
Remember that the "Geoid Model" is theory. It's commonly used in professional practice, just be careful about guaranteeing the current U.S. government "best guess."
Accuracy Statements about the Geoid are DANGEROUS
> Remember that the "Geoid Model" is theory. It's commonly used in professional practice, just be careful about guaranteeing the current U.S. government "best guess."
...which I believe brings up the whole issue of network vs. local accuracy.
Accuracy Statements about the Geoid are DANGEROUS
Remember that the "Geoid Model" is theory. It's commonly used in professional practice, just be careful about guaranteeing the current U.S. government "best guess."
Really? Those geoid models aren't perfect? Who knew?:-(
It would be nice if surveyors would test their vertical results against established bench marks and their own level runs to see just what kinda of error their GPS units are producing. I know some that do and some that seem to think GPS and OPUS is gospel. Oh well:-)
Duncan Parnell has a course on their web site with a spread sheet that was developed to do just what you are asking. $40 if I remember correctly.
If reporting in State Plane in CA, the accuracy statement is required.
