This is one I've never encountered, and I have a made and seen some crazy mistakes. I went over an hour away to do a "slam dunk" ALTA on less than an acre I surveyed five years ago. I had already done the difficult part and now had the chance to ground truth myself, which is never a bad thing. Topcon GT 503 robot with FC5000 running a fairly new version of magnet. I'm home now and didn't remember to see what version. I setup the traverse to have multiple cross-over ties to give us lots of redundancy. I couldn't get a 200' tie better than 0.04' and most around 0.08'. I also closed a loop around it. Had a total of 6 seconds (6 setups) in the angles. Linear was out 0.12'. No way that would meet the standards. We checked everything we could think of. Multiple times. All good. So I drove back very puzzled. Went in early this morning to make some minor edits to the raw data to run through SURVNET. I was hoping that it may point out something. I had the raw file edited and was about to save and close it when I noticed something. Every distance was to the nearest tenth of a foot. I went through the settings on the FC5000. All correct. Got the robot out to look at the settings and noticed that every manually triggered distance (no DC involved) was nearest tenth. Finally found the settings and fine mode resolution was 0.001, rapid was 0.005 and tracking 0.1. So as I see it, when the DC was set to tracking, the robot (because of its internal resolution setting) only output distances to the DC to the nearest tenth. Does this theory hold water? Did I or the other operator possibly fat finger something to cause this? Is it a glitch? I have been using the robot for a year with no issues of this sort. Rounding can't be adjusted out so I'll have to do it again. I still have scars on the backside from the chewing out I got in the days before surveying equipment had batteries... So I'm not green. I'll also accept it if I fat fingered something to cause it. Thoughts?
Stacy
Go into Magnet and set all measurements to fine, not tracking. Makes changes in stakeout also.
Data looks like you confirmed everything with 0.1', you could accept the original values and call it a day. How precise were the angles?
Paul in PA?ÿ?ÿ
Have changed those settings a dozen times. They don't stick
When guys say, "settings dont stick" in Magnet, we generally discover that they aren't checking the settings of the new job by clicking "Next" at the bottom. They are simply clicking the green check at the top at the first screen. This matters because if you open an old job and then start a new one, the current job is essentially the template for the new one. Sure, if anyone that actually surveyed wrote the program, it would have a couple of templates for new jobs to select from, but this is Magnet we are talking about here.
Yes, tracking is nearest 0.10'
Why anyone would want that on a GT-503 is beyond me. If you only need a 0.1', there are lots of cheaper options.
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From the minimum standards:
- The maximum allowable Relative Positional Precision for an ALTA/NSPS Land Title Survey is 2 cm (0.07 feet) plus 50 parts per million (based on the direct distance between the two corners being tested). It is recognized that in certain circumstances, the size or configuration of the surveyed property, or the relief, vegetation, or improvements on the surveyed property, will result in survey measurements for which the maximum allowable Relative Positional Precision may be exceeded.?ÿ If the maximum allowable Relative Positional Precision is exceeded, the surveyor shall note the reason as explained in Section 6.B.x. below.
- A note on the face of the plat or map explaining the site conditions that resulted in a Relative Positional Precision that exceeds the maximum allowed pursuant to Section 3.E.v.
Not sure what your explanation would be though. "The interaction of my data collector and total station are opaque to the point of my having no clue why my $20,000 investment in precision equipment only provided me with $1000 in precision."
If the angles are tight, and you are on old control (or tied to it), have you attempted to use the previous observations? Your least squares software should allow you to assign specific parameters to each measurement, and the new ones would have say 0.06' (minimum) of possible "error" assigned to the distance measurement.
If you passed last time, I doubt the control has moved enough to cause a failure this time.
I actually woke up during the night Friday night and thought of trying that. It actually passed ALTA specs. Didn't expect that at all. I am going back to rerun anyway. I'm interested in the accuracy of the distances that the software computes from the rounded ones
