I would like to know a methodology for traversing between two known points that cannot see between the two points. That is you cannot occupy one point and see the other.

At Ohare airport in Chicago I have several known monuments. I would like to traverse between two points to establish control between the monuments. However, if I start on one point I will not have a known back sight. Also, the two points are not within sight of each other. Several turns will be required.

How do I go about this with no backsight?


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Can you use Gnns receivers or only conventional surveying?
Conventional please
Better use gnns rather than conventional method.Has.it favoured you
In TRIMBLE Access using the traverse program it walks through the steps & gives me great results
Dang I use Leica
i think if you can have access to GPS you can use it. if the place is complicated for gps just use it to establish an inter visible contro

Hi Chris,

If you have  points that you have coordinates on ,(but no BS point,then  set one) and assume a bearing or AZ. Then run your new traverse to your other known points with assumed bearings or Az. Then close the loop and you have a close traverse. Then you can adjust,as rotation and ( translate if assume coordinates are used ) on the new traverse. And  apply survey adjustment if needed.

Because you know the bearings and distances between the known points. what you don't have is a reference line for a known azimuth BS to start from.Now you can calculate one with this new Data.

Or maybe a simple Resection or triangles will solve this,but if not run the closed traverse loop and Translate and rotate to the known points.

standard survey problem.

hope this helps.

Billy has it.

Set a random point you can set on and then backsight known point A, with a distance. Because I confuse easily, I would use a bearing that is similar to a compass read :)

Shoot the bacsksight distance, then set your forward point, and so on.

Once you've shot your known point B, you can calculate the distance you've measured between your A-B, and compare to the known distance A-B. Then translate and rotate and adjust if necessary.

Perhaps you can survey a trajectory from A to B with several stations in between.
Than go back almost the same route from B to A.
Your starting backsight would be the last point from the way back.
This way you create a closed polygon. The total sum of the readings will be (n-2) inside or (n+2) outside angles.
Start with a local coordinate system, work from A to B and if you come back to A, comming from B. The coordinates of the starting position should be almost the same as the end coordinates.
After that a transformation from your local coordinates to the Monument system.
If the calculation is a bit difficult, you can do it in a Cad program like Bricscad or Autocad.
Hope this helps. It's only one of many solutions.
But always create a construction that can be proofed, and buy a good book!
Succes from the Netherlands

White, the obstacle.

Red,; known control-points.

Yellow; temporaly points.

Magenta; observations.

Just take a Sun Shot or a Polaris Shot for Azimuth.

how about resection method? i think that's can solve the problem as long as the two known points are still can you see them from another point of view..


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