California Surveyors Forums

I'm a surveying student and could use some help determining the average vertical angle from a given pair of vertical angles. For example: 280°59'01" and 10°59'51".

10 59 25

Those two angles don't even relate to each other if they are zenith angles.
They look like they are referenced to a 270°, one being a zenith angle and the other an angle of elevation with 0° being "level".
280°59'01" has an explement of 79°00'59".

Terminology is zenith, horizon and nadir (pointing vertical circle zeros).
Is this question talking about same type of a vertical angle or is it expecting you to make a difference between horizon and zenith reading?

Hi Surveyor3
The answer is probably 10-59-26 but I doubt that is helpful, if you post the question in its entirety there can be a meaningful explanation

My guess is that the given angles are from two different instruments and Jay Wright is then correct.
However, an angle that isn't doubled in some fashion isn't an angle.

Dave Lindell wrote: Mon May 02, 2022 2:46 pm My guess is that the given angles are from two different instruments and Jay Wright is then correct.
However, an angle that isn't doubled in some fashion isn't an angle.

Love that!

Unfortunately, this was all the information I was provided. That may be why I am having some difficulty.

LOL! Maybe they shouldn't have Phd s teaching?

It looks as if the the 10°59'51" should be 100°59'51" (direct reading). With the 280°59'01"(reverse reading). When turning vertical angles you can not double them! You can only read direct and reverse. We average the minutes and seconds only to remove any index error that may occur in the instrument. In this case we have 59'51" and 59'01" average these numbers and add to your direct reading. 100°59'26".

tmack that is quiet obvious! NOT

I'm sure you solved the riddle correctly. Good thinking

If both of the given angles were zenith angles, then in theory, they should add up to 360 degrees. Therefore 280°59'01" and 100°59'51" would not make sense.

No the vertical angles will not add up to 360°. The angles should be 180° opposite. ie 100°59'51" and 280°59'01". Then adjusted to remove the index error.

tmack: what kind of instrument are you using?
Horizontal angles do as you say, that is measure 180°different.
Jon Olin is correct for every instrument I've ever used.

Does it matter what instrument I use? You can only turn vertical angles in direct and reverse mode. It is not like the horizontal scale were you can double and wrap it up as many times as you want.

I just don't know of any surveyor's instruments that measure vertical angles 180° apart when measured direct and then reverse. Enlighten me.
(Direction instruments can't "wrap up" horizontal angles.)

Oops! Double post!

My bet is his prof never used anything and pulled the question out of an ancient text book, then made a typo.

If I recall correctly the Old open wheel transits read that way when you flipped the scope. Not gonna rummage through my junk and check...

I have one of those old transits of which you speak, and both the direct and reverse have scales that read 0° when leveled.

Oh, and there is one time the vertical circles on a theodolite will agree by 180° and that's when it is pointing perfectly level and the readings are 90°00'00" and 270°00'00".

Well it looks like I am totally wrong. I will eat humble pie.