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Carlson compass rule challenge  


Allen Wrench
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I have some plats I'm recreating on behalf of some GIS folks.  They are fairly modern metes and bounds plats, typically with several thousand feet of traverse (not always closed on themselves) with a precise GNSS coordinate at each end.  The coordinates are grid, the distances of the traverse lines are ground.  Everything on paper looks just fine.

Is there a way to have Carlson hold the starting coordinate, adjust the angles and distances of the lines (proportionately) until it hits the point at the other end?  What's the "best practice" or basic way to go about this?  Do I have to key it in as a traverse?

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Paul in PA
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First of all, you have to decide if you are going to continue your project in grid or ground coordinates. You cannot combine them.

Typically I hold one grid coordinate and scale all others to ground. I do it in a CAD drawing with an untouched Grid point layer, and similar points on a scaled layer with number a 1,000 higher. I lay in my field points and rotate to the scaled grid points and compare. If everything is in the range of my GPS and field points precision, I am done. There is no need to scale or adjust my honest field work. Precise agreement is way too overrated.

Paul in PA

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Peter Lothian
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Survey > Polyline Tools > Compass Polyline Adjustment

That would be the simplest approach. Your end result would be a polyline with Grid distances.

Another approach would be to run your lines through a least squares adjustment with Surv*Net. Much more complicated, though, and you'll have a really cool output file. However, the results will not be much different from the Compass Polyline Adjustment.

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A Harris
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When my GPS locations are relatively close (within a tenth) to my TS measured values, I simply rotate and keep both values.

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Allen Wrench
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Thanks for the replies.  It's going to be totally in grid, since that's the precise coordinates I've been given, and I'm just passing the lines on to the GIS folks so they can tighten up their maps.

The map I have now is dimensioned to the nearest second and hundredths of a foot and the math works out just like you think it should.  The problem comes in when I have a map where it's a modern survey with precise GNSS points at each end, but the boundary lines are only labeled to the nearest minute and tenth of a foot.  I need to arbitrarily adjust so that the linework is as close as it can be, considering the information I'm working with.

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