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with all the newer receivers and channels and satellites, the methods are evolving still and should be tested in the organization for the best results for crew work flows.
the default setting for 180 epochs in observed control point with trimble had been there since 2005 when I started using GPS. Lots has changed.
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The 3 minute time and Observed control point option in Trimble Access is for allowing Trimble Business Center to do more with that observation in Network Adjustment.
As long as long as you have cell service why not use one the net services of Leica (SmartNet) or Trimble and get the best of both worlds and you can then use the data from their reference stations or other CORS to perform post processing if you're really wanting high accuracy but you mentioned plus or minus a foot so we're starting to compare apples to oranges as to what method is more accurate. With network RTK and a 10 second occupation I typically get +/-0.10' (XYZ) using Leica's SmartNet even on the fringes of their availability map.
Is there any chance anyone could use this as an example of how to explain convergence angles and why/how they??re needed to adjust what sounds like an open loop traverse? What IS the difference between doing it the OP??s way and doing it Mayers way? Aside from the longer baselines (which I thought I was hearing weren??t that great for corrections), and assuming reasonably consistent orthometric heights over the 7 miles, does one method make the Compass Rule less heavily burdened by different convergence angles and scale factors? Does it depend on whether the 7 miles is North-South or East-West? If the OP had a BOB between the initial/terminal ends of the traverse, while Mayer had a BOB between his two [remote] control points, would there be any difference between how you would present the coordinates of your control network?
With GPS adjustments you don't even get to convergence angles or scale factors or XYZ coordinates.
Coordinates are simply functions of the underlying data.
It's relatively simple to adjust GPS networks without any coordinate system applied. Even a compass rule adjustment should be simple to apply to Lat, Long, Height data. Not that I would do or recommend it, but it should be easy to do.?ÿ
If you want to use GPS there are many least squares programs available for the purpose of adjustments.?ÿ
Normally for a corridor survey we wouldn't even look at the XYZ until all adjustments were completed.?ÿ
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Each grid point will have a convergence angle and each point will have a scale factor,?ÿ but they don't play into an adjustment of the measurements.
Note that while a CR adjustment operates on the coordinates it should be thought of as an adjustment of the measurements between the points.
convergence angles and why/how they??re needed to adjust what sounds like an open loop traverse?
The main reason convergence angles would be used in "open loop" or "link" traverses was because it was not uncommon to have two geodetic bearings at each end of the traverse (usually to a reference or azimuth mark, or from an astronomic observation thereof). It was necessary to apply the convergence angle at each end to find the grid bearings, so that when you went to perform your adjustment you were working out the math in a projected Cartesian coordinate system.
With a closed-loop traverse, strictly speaking it doesn't really matter whether you apply a convergence angle or not, because the starting and closing leg are one and the same.
@bill93 That's a great chart and coincides roughly with some testing I did a few years ago with a GPS + Glonass Javad Triumph-LS. I found that 4 minutes seemed to mark a point of diminishing returns in precision.?ÿ
I shared this on the Javad message board, and I'll share the highlights here. I've seen the epoch by epoch scatter plot of the vertical position of the RTK solution and over time it takes the form of a sine wave. I suspect the reason that 30 seconds tends to provide poorer precision than 5 seconds is because the 30 second observations may tend to be biased on one part of that wave (including only the peak or the valley of the wave and not some of both). I suspect this may be why the precision at 180 seconds is not below the straight line between 60 and 300 the way the horizontal precision is. Perhaps the 180 second average includes a full cycle or more (I'm referring to the cycle of vertical plot, not carrier phase cycles), and part of another, thereby partly biasing the solution to one or the other. Preferably, the average would include some n number of whole cycles of the vertical plot and not a fractional part.
Just a thought.
Also, multi-constellation RTK provides better precision faster in my experience. So this chart is somewhat antiquated at this point for most modern RTK systems, although the concept still applies.?ÿ
