A local company did a subdivision plat for a tract of land west of and along a water course last year, there were about 60 courses generally from just east of the west 1/4 corner of a section to just south of the north 1/4 corner.
These lines were not monumented and I now have a client to the east of the water course that needs a survey of about 40 of the lines.
I have the W1/4 and the N1/4 now located and we are both using state plane bearings and surface distances. The sixty courses were imputed into autocad and then inversed, the results were thus:
record inverse: S44-16-50W, 3734.20'
measured inverse: S44-16-48W 3734.20'
basically a flat closure, about 0.03' in the angle.
Both surveys were RTK with no dimples;-)
> record inverse: S44-16-50W, 3734.20'
> measured inverse: S44-16-48W 3734.20'
I'll bite. So, basically what you're saying is that two surveyors located two monuments roughly 3734 ft. apart and got relative positions that differed by 0.04 ft.? What's novel about that if GPS was involved? Or is the novelty that two RTK surveys agreed within 0.04 ft.?
Actually agreed by about 0.013 ft. But, they coulda agreed even better, if the seconds were carried out to the tenth of a second.....
🙂
Nate
> Actually agreed by about 0.013 ft.
But sin(0-00-02) x 3734 = 0.04
OOps. The calculator I grabbed, does the DMS DD thing different than my normal calculator.....
My mitstake.
N
Novel? Nothing novel about it lol, sop
> Novel? Nothing novel about it lol, sop
Just out of curiosity, what was the uncertainty in your own measurement of the bearing and distance between the two monuments in question? Do you know what the uncertainty of the result from the earlier survey was? If the answer is "I don't know", is there some way that you might?
I'm 100% certain both surveys are using the same monuments.
> I'm 100% certain both surveys are using the same monuments.
Yes, that's nice, I'm sure, but the question has to do with the uncertainty in the bearings and distances reported by the two surveys. Presumably it's understood that professional surveyors try to figure stuff like that out before someone comes along and alternately says:
- "I'm missing you by 0.04 ft."
- "I'm missing you by 0.40 ft." or
- "I'm missing you by 4.00 ft."
> Novel? Nothing novel about it lol, sop
It is quite possible to do excellent work with RTK. It is equally possible to produce very poor results, and difficult to tell the difference at a glance. That is also true with traversing, of course. But I think that the principles of error trapping RTK work is generally less well understood than that of traversing.
Which I believe is Ken't point. All measurements have uncertainty, the professional needs to qualify and quantify.
In other words, what was the proceedure? A single observation, multiple observations over a reasonable time span or multiple observations over multiple days? How can you have a certainty with a single observation?
> Both surveys were RTK with no dimples
I do recall being in situations where I got the same wrong answer all the time. Funny how that works.
Kind of like taking a 2x4 and cutting it once. Then it's too short so you cut it again. Then it's still too short so you cut it again....
I can't recall a single time I've found any real "error" retracing RTK surveys in years, there are reasons for RTK to fail, but the people I've been following have those under control. Which is a good thing;-)
Maybe it's the part of the country I work in, but record data is much, much tighter than before RTK came along.