Validated and Verified observations disagree !?

I collected these points yesterday. They are both shots on the same nail set, and both observations went through the Ph1- 3 validation process. The only reason I caught this is because this was one of two points collected in order to calculate a dist./dist. intersection to an inaccessible property corner, but the COGO routine gave a "no solution" message, which prompted me to check on the two nails set for the offsets. Pt. 51 is the first observation (and the "bad" shot) and pt. 54 is the second observation, which was good; both are on the same nail. The offset nails were close enough together that I could lay a tape down and check them manually.
The "boundary" profile settings used for these observations are: min duration 120 sec, phase 1 min duration 60 sec, 2 engine min, validate with at least 2 engines, verify with V6 re-set, 100 epochs, consistency 20. I was running on a subscription RTN.
This is very concerning, as I have always trusted the validation routine (it is what sets this GNSS equipment apart from others), and now I have to wonder, how many times this may have happened in past?
Maybe someone out there can look at these screen shots and see something I am missing. Any ideas or thoughts about what may have happened here would be appreciated.
 

Attachments

  • 20210123-13.21.07_00322_Point_Info REESE54.png
    20210123-13.21.07_00322_Point_Info REESE54.png
    30.7 KB · Views: 234
  • 20210123-13.21.23_00322_Point_Info REESE51.png
    20210123-13.21.23_00322_Point_Info REESE51.png
    30.9 KB · Views: 231
  • 20210123-13.21.44_00322_Inverse REESE 54-51.png
    20210123-13.21.44_00322_Inverse REESE 54-51.png
    28 KB · Views: 244
  • 20210123_121642.jpg
    20210123_121642.jpg
    4.2 MB · Views: 207

Nate The Surveyor

Well-Known Member
Ok, so is this the std LS?
I have mine set for 200 seconds, with verify at the end. I think 120 is not enough. Shawn Billings uses 180, last I heard.
I have never run rtn. So this may not be apples to apples. It looks that they are 4.11' apart?
Shawn is on the LS+.
The LS+ is different.
If you're is the std LS, 6 engine, min phase 2 is 180. Even then, in very challenging places, there can be slop, such as 0.6' error, by a huge tree. Any shot by big trees, gets either shot 2x, begin a second observation, and get some extra clicks, with resets.
Hope this helps.
N
 

Matthew D. Sibole

Well-Known Member
5PLS
If using the standard LS I have a minimum confidence level at 25 and want to see a total time between fixed epochs at 240 seconds or more. Point 51 does not have nearly enough time.

I always preach multiple observations to be able to catch blunders. Nothing like looking back at old data and knowing for sure it is right because you have 2 or 3 shots that are within hundredths of each other.
 

Adam

Well-Known Member
5PLS
Like Matt, I always shoot important points twice. Very rarely do I have a bad shot but it happens. When it happens I know it right then and I know to stay until I get some agreement. RTPK has made the LS (standard or plus) have more redundancy automatically but I still shoot points twice. 2 shots helps me sleep better at night. In the scenario of the DD intersection I don't normally shoot each anchor point twice but will check them with a tape like you did.
 
Jack: I use the same double-offset method you do, including closing the triangle with a third taped distance. Have you tried using the 'Tilt' method for a direct shot on the pin itself? it's somewhat complicated to set it up (there's a separate thread somewhere about that) but, it could provide a third check on your offset shots in a tough setting.
 
Top