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Conference Competition Help
Posted by gabe0512 on March 26, 2019 at 9:43 pmHello, I have a conference coming out and need help with the approach to solving the problem. I am given N,E,Z and a fixed back sight for starting location, and am asked to traverse to two locations, and then find the N,E,Z of an inaccessible point. I am not sure what approach to take. I will be using a LEICA total station model #TC407.
Any help would be greatly appreciated. I have attached the complete rules for more clear details.
Thank you.
davekaroly replied 5 years, 6 months ago 9 Members · 11 Replies 
11 Replies

You have to triangulate in a point from known points that you traverse to. Keep good notes and write down D & R angles, vertically and horizontally. I always preferred to put the actual AZ on the backsite, but that depends on the total station, sometimes it’s better to turn 0’s and add and subtract angles. So I guess you have to turn to this unknown point horizontally and vertically and solve triangles to get your N, E, El.
If you understand sin, cos, tan this is a simple process. Once you solve the triangle calculate an az from each point and use the solved distance along each leg of the triangle and get your N, E. Then use the distance to get a new elevation from your two traverse points, by applying a sin or cos to the vertical angle (which one depends on if you use a vertical or zenith angle), adjust the elevation, no doubt you will have a couple of different answers. If it’s more than 500 feet apply curvature and refraction.
They want to see your calculations and field book, use a straight edge, show the traverse, triangle, calculations, you should do well. All you need to do this is a calculator with sin, cos, tan functions and pencil.
Have fun.

Ok, well it says you are to demonstrate your skill.
Is this a demonstration of your skill, to find this forum, ask some surveyors, and go compete?
I can sorta see it as a skill, (I have a little brother) One of his skills, was to see who he could get to do stuff for him!
So, why should we help you?
(Big brothers ask stuff like this!)
Go show em your stuff!
Be a sport. Win, loose, or have fun.
Tell us a compelling reason to help you win…. 
It would not be much of a competition were the professionals to give you what your professor has already taught you.
good luck

Presuming that simple traversing is within your abilities……
You get the horizontal position by BrgBrg intersection from your 2 traverse points. Once you have that position you can inverse the horizontal distance from the inaccessible point to the 2 traverse points. And with that in hand, together with the zenith angle to the inaccessible point, you can compute the elevation.

Around here, some profeshunul surbeyers just guess at it!
ðŸ™‚

Norman and MightMoe gave good instructions. And, ease up Nate, this engineering student is asking surveyors for help!
This is a surveying competition at an ASCE regional student engineering conference later this week, but I must have missed when the ASCE decided to update the term “field crew” to “ensemble.” Geezo, Wheezo!
On Tour will have ensembles applying their knowledge of geomatics and their land surveying skills. Ensembles will bring their surveying instruments On Tour and triangulate an inaccessible point.
Since accuracy is 33% of the score, I’d suggest before you show up Thursday, that you double check the level bubble on the rod and follow the instructions on “checking and adjusting ” your TC407 in the user’s guide and verify that the tripod is in good order. Also, doublecheck your heights of instrument or you will be sorry.

Thank you all for the feedback, our team will do the best we can!

The rules constrain you in about everything except choice of the two observation points and your calculation sequence. Preparation will win the day.
When choosing points, assuming line of sight is easy to get, you want to make sure you are creating something not too far from a 90 degree angle at the inaccessible point. That intersection angle is important because you are doing a bearingbearing intersection with no direct distance measurement there, and subject to what I visualize as the “scissors effect” where a small change in a small angle creates a large change in intersection distance. The choice of other angles isn’t as important because you will have both bearing and distance for them.
I’m not sure why you need to traverse to two new points instead of using the given point and one additional point. Maybe there is a line of sight issue, a poor geometry issue, or maybe it is just a rule for the contest.
Know what tension to use on your tape, and if sag and temperature corrections are appropriate.
Know what function each crew member will perform so there is no need for onthespot planning and activities can go on in parallel.
Don’t set up the tripod with a “beer leg,” i.e., a leg blocking the path of the tape.
Decide if measuring the distance between your chosen observation points gains enough checking and possible improvement in accuracy to be worth the time. That distance can be calculated from measurements you need between each point and the given starting point, and another measurement costs time, but a check is nice.
Practice the calculations ahead of time, using realistic values, so you will be fast and get a decent time score. Figure out what your field book layout will be so you end up with a neat presentation for scoring.
. 
An exercise designed by the ancients to see if an old surveying method is still being taught. I would guess not so much, due to modern technology. Hint: google quadrilateral control surveying, or something like that. Should you send one of your ensemble to the unknown spot with cell phone gps for a check? Which solution would be more precise? More accurate?
These things should be a learning experience rather than a gee in my day we would have learned that by now test.

Hint: many surveying field books have the diagrams to solve triangles in the back of the book. I can’t see why you can’t use a standard one of those.

Do a deflection angle traverse, simplifies calculating the next bearing ahead.
Backsight, plunge the scope so that you are looking the other way being careful to not disturb the horizontal angle. Then turn left or right to your foresight (be sure to write down L or R as appropriate). Then backsight in Face 2 and do it again. Average the deflection angles.
Say the backsight bearing is S 400000 W…convert that to N 400000 E (from BS to your instrument). Say the deflection angle is R100000 therefore the next ahead bearing is N 500000 E. Then say the next deflection angle is L150000 therefore the next ahead bearing is N 350000 E then say you look L400000 (now you have crossed the quadrant boundary) so your next ahead bearing is N050000W. Simple which is why the oldtimers did it that way.
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