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Resection Problem?

Hi.

I have computed a resection from 3 points with 2mm(X), 0.8mm(Y), 1.2mm(Z). The height of the computed points is perfect but as you can see in the highlighted image all of them are rotated. Any thoughts of how can I avoid these things to happen in the future or maybe which may be the possible source of errors in this case?. I had the resection points placed in 3 quadrants so the geometry was as good as it gets, the distances were about 40m for the first resection points, about 20m for the second one and about 28 for the third one.

Thanks

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  • I usually use a SAS (side angle side) solution to solve the triangle, then use the closest know point to traverse to my setup, using the calculated angle to solve the bearing. This helps push the error as far away as I can from my area of work.

  • GeoEducator

    The reply wrote Dadallage is truth, from brant to brand the name can change and the procedure too.

    but i'm according to Arie Lise: you get the location but not orientation so you need to beging as usual you do at the beginig of any work.  Adittional you must to regard the math problem of this procedure: you're calculating the coordinates of your station (3 unknows data: x,y,z) so you need at least 3 points. the software can apply a 3 simultaneous equiations but you're loosing the power of the software. if you back side 4 o more points the software can apply a least square procedure so the accuracy of the x,y,z unknow point can be improved.  Remember: all measurements have an error, additional to mistakes.  The accuracy of your results depends on the accuracy of the points you're taking as benchmark

  • Hello 

    Firstly can i get the idea about your equipment which Was used for this work? (Brand and model)

    Then we can give clear answer for your requirement Becuase resection procedure is different with brand name.

  • A lot of field software require that you do a back-sight after you do a resection.  The resection just gets you the location, not the orientation.  Once you have the new point you have to set it as your occupation and then back-sight.  Dumb, and probably less accurate, but the command where it does your orientation is usually an extra function they want more money for.

    Not to be nag, but also remember that you have 3 unknowns (x,y,z) and you only used 3 points.  That is a perfect solution with no redundancy.  Use a fourth and you will get worse residuals....but a more true picture of your actual accuracy.

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