Bearing Direction

[MOOK]

This problem is in Reza Book:

The latitudes of closed traverse failed to close by +0.30 and the departures failed to close by +0.45.

What is the bearing of the closing line?

The answer is S 56 18' 36" W

Why not N 56 18' 36" E ??

How can we determine the direction E,W, N, S??

Thanks?

 

[Desert Engineer]

Those bearings describe the same line, with a different starting perspective.

 

[MOOK]

Those bearings describe the same line, with a different starting perspective.

I know that but one of them is right and the other is wrong, so why is S-W is the correct one?

 

[sac_engineer]

Those bearings describe the same line, with a different starting perspective.

I know that but one of them is right and the other is wrong, so why is S-W is the correct one?

Because you're going in the direction FROM the last point TO the starting point. The +.30 and +.45 are relative from the starting point. Think of the starting point at (0,0) and the end point is (0.30, 0.45), then the closing bearing is in the S-W direction.

 

[MOOK]

Those bearings describe the same line, with a different starting perspective.

I know that but one of them is right and the other is wrong, so why is S-W is the correct one?

Because you're going in the direction FROM the last point TO the starting point. The +.30 and +.45 are relative from the starting point. Think of the starting point at (0,0) and the end point is (0.30, 0.45), then the closing bearing is in the S-W direction.

What do you mean by the closing bearing?? If the start point is (0,0) and ending point is (+0.3, +0.45), the direction from the strating point to the ending point will be N-E not S-W.

 

[EnvEngineer]

What is the bearing of the closing line?

You are not going from the start point to the end point, you are going from the end point to the start point to close the traverse.

 

[jamie]

maybe looking at it another way - if I'm thinking about this correctly, then the reason you are going in the negative direction is because in summing up the lat and dep you had a positive error for both (too many of each in the positive direction). to correct this, the closing line has to go in the negative direction, because you need to subtract that amount.

 

[kevo_55]

^^ Winner!

That's how I think about this issue with surveying.

 

[parthurvt]

This leads me into a question I had in an example in the Cuomo book. On page 40 they correct a travise by adjusting the latitudes and departures each by a portion of the total error, but there doesn't seem to be any particular rhyme or reason to it. Am I missing something?

 

[jamie]

they distribute the error out to all segments because without knowing where the error came from, it can only be assumed to be a cummulative error from all the measurements. so it gets distributed out to them in proportion to their length. there are other ways of adjusting and correcting a traverse, that's just one of them.

 

[parthurvt]

thanks jamie, I feel a little foolish now because they explain exactly that just a few pages later...