Deflection Angle

[305Gurl]

If I have a line at N43-degree,10-minutes W that meets another line at S15degree, 12 minutes W, would the intersecting angle calculated as 180 degree minus the sum of the two angles = 121degrees 43 minutes?

I think I have this correct but sometime gets frustrated in the answer on these easy problems. CERM does not go into details in doing these problems.

 

[ptatohed]

I get I = 121^ 38' as well. Attached is my schematic.

Edit: Okay, I give up... I can't seem to get the image to upload right now (it hangs up even though, it's a small file). I'll try again later.

 

[civilized_naah]

If I have a line at N43-degree,10-minutes W that meets another line at S15degree, 12 minutes W, would the intersecting angle calculated as 180 degree minus the sum of the two angles = 121degrees 43 minutes?

N 43d10m W has an azimuth of 360 - 43d10m = 316d50m

S15d12m W has an azimuth of 180 + 15d12m = 195d12m

Intersecting angle = 316d50m - 195d12m = 121d38m

 

[ptatohed]

I couldn't get my sketch to download straight from my computer so I had to host it on photobucket. Anyway, here's my chicken scratch:

 

[305Gurl]

Thanks to ptatohed for the excellent graphic details and also to civilized_naah for a different approach to this problem. It's a bit clearer now.

On another note, if I'm given a bearing that runs N43d-10minutes and then there is another unknown bearing (which I need to find) that appears to runs in the southwest direction, based on the diagram that is provided in this problem (they intersect each other, and the angle between them is 58d-22minutes). Is this the deflection angle given as 58d-22minutes? or deflection angle only apply to horizontal curve and now we are dealing with bearings segments that may or may not be a curve. Is my assumption correct? This is another thing I want to clear up before the exam.

So, if I apply the same rule for finding deflection angle, then I would be dead wrong with the answer I find ? The solution states that Bearing 1 + Bearing 2 = the angle b/w the two. When this formula is rearranged, Bearing 1 = the angle b/w the two bearings - bearing 2 = answer or B1 = 58d-22minutes - N43d-10minutes = S15 degrees 12minutes.

Is this a general case that can be used all the time with these types of questions?

Thanks again!

 

[ptatohed]

305, if I understand your question correctly, you're basically asking which angle is the deflection angle of two intersecting lines (whether or not there is a horizontal curve). Could you post the original problem? I guess I just assumed it was a horizontal curve question but, you're right, that isn't necessarily true. Anyway, the deflection angle is the angle that the instrument needs to turn to go from bearing 1 to bearing 2. It's equal to I or /_\. Imagine an instrument on one of the bearings (either one but let's say the N 43^ W bearing). So the instrument is at the PI facing N 43^ W, right? What angle would the instrument need to turn to face the other bearing (S 15^ W)? The answer is 121^ 58'. Does that make sense?