SURVEY QUIZ for 2 July 04

[Ralph Jones]

Good Evening Friends,
If you are laying out a parcel of land using an instrument or compass and are shooting a line of sight of 135 degrees, what is the back azimuth?

Respectfully,

[AlexS]

315 degrees

[Robert WA]

135 + 180 = 315.

[forunna]

I'd call it a Back Bearing. but that comes from a navigation perspective rather than a surveying perspective. (asuming you are talking about the 180 deg reverse like my learned freinds here have done)

[bitingmidge]

I'd call it "scope of work" for a surveyor!

Cheers,

P

[Ralph Jones]

Good Evening Friends,
The correct answer for the quiz is 225 degrees. How you find it is as follows;
a circle is 360 degrees and when you subtract 135 from that you have the back azimuth of 225 degrees.
Now to check our selves, anytime you have an azimuth of more than 90 degrees you add 90 degrees for the true back azimuth and any line of sight less than 90 degrees you subtract 90 degrees to arrive to the back azimuth.

when I was in the Air Force I was a member of a search and recovery team and when we went out on a plane crash I would act as the plotter, where I would be furnished with an overlay of the area of the crash and used this method frequently, with a grid co-ordinance of a 12 grids.

Thank you for your support.

Respectfully,

[bitingmidge]

Any wonder I keep getting lost.

Navigation in the States sure is different to here!

P

[Ralph Jones]

Hello Midge,
Even if you don't have a compass you always have a sense of direction as the sun rises in the east and sets in the west and moss grows on the north side of a tree, so if you lay one stick on a horizontal line that would be laying east and west and another stick toward the moss on the tree you have a natural compass or sense of direction.

A lot of people get lost because, they can't see the tree for the forest.

At night with a clear sky you still have the brightest star in the sky with the north star, to guide you.

Respectfully,

[bitingmidge]

Ralph,

Do us a favour...don't go walking in the bush here alone will you?? :eek:



Just a few subtle differences: Moss grows on the southern side of trees if you can find it... since we live on the dryest continent on earth, moss it a bit like rocking horse manure in most parts. Of course if you live in Kuranda (with Journeyman Mick), you'd find moss growing on the bottom of your cereal packets at breakfast, on your toothbrush, and just about anywhere else really.

The north star is just a bit over the horizon for us to see mostly as well... I can't say that I've ever seen it. We tend to rely on the Southern Cross (which is the group of stars which feature on the flags of Australia and New Zealand) and has a couple of stars which point directly south.

The sun does rise in the east, so you'd be ok there. There is a bit of a trick with finding north using a wrist watch. If you hold your watch horizontally, with the hour hand pointing at the sun, bisect the angle of the hour hand and the minute hand and the resultant line will be running north-south.
(Doesn't work with digital watches though!)

Hope all of that gets you out of trouble when next you are downunder!

Cheers,

P

[DavidG]

Don't think so.
1. Back on 135 is 315. See attached diagram.
2. Moss grows on the southern side of trees down here
3. We use the southern cross with the two pointers to derive due south. The north star is not visible from Oz.