Resection

John Thompson

Well-Known Member
I sent project Vernon to support.

I used Resection to calculate the coordinates of a point I couldn't occupy directly.

Base was autonomous. Used Real-time Position Shift (Point 1595 to PLAT_1_7).
I calculated 1602 from 1599, 1600, and 1601 using Collect-Point-By Offset-Resection.
In the field I inversed from 1602 to PLAT_1_10. It was close. I don't remember how close. Under 0.1'?
Back in the office I corrected Base with DPOS. CORS correction was 4.13' Horizontal and 3.57' vertical from Auto position, but only 0.049' Horizontal from the 1-Local position.
Exported CORS-corrected points. Point 1602 is now 4.176 feet from PLAT_1_10, and has an elevation of -3.587'.
I went back to the Collect-Point-By Offset-Resection screen which was fortunately still populated with the coordinates and offsets of 1599, 1600, and 1601. I saved point 1604, which is 0.161 feet from PLAT_1_10 and has an elevation approximately equal to the average of the 3 points resected from.
20180906-10.50.00_00229_Resection.png

If I change the Base back to the Auto coordinates and inverse between 1062 and PLAT_1_10, I get 0.046', probably what I saw in the field. But in the field I was using Shift, not Auto.

Questions/Observations.
1. Calculated coordinates from Resect don't seem to be working properly with Shift and/or DPOS.

2. How is the elevation of the calculated point determined? Apparently not a simple average.

3. It might be a good idea to attach the Resection screenshot to the calculated point so I could later review how it was calculated and what the residuals and offsets were.

4. Are the coordinates for Point 1604 correct?
 

Adam

Well-Known Member
5PLS
You can use the shifts function in cogo. There is a dpos button that will populate the shift value from dpos.

Weighted, I think.

I think all the cogo screens have a screenshot check box if you tap the icon with the surveyed point info. I don't have mine in front of me at the moment.

1604 is relative to this coordinates in the box. They don't update after dpos unless you repick the point.
 
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