StarNet Direction Set Data Types - Difference Between Direction and Angle - Types Of Theodolite

Steward Souten, post: 431953, member: 12714 wrote: I guess the fundamental point is that I don't understand the difference between a direction and an angle.

This is truly fundamental stuff, so a basic surveying textbook might be a better place for you to start. But basically, a direction is an angular measurement taken at a given point with respect to a known directional reference (e.g. geodetic north), while an angle is the angular quantity taken at a given point between any two other points.

A repeating theodolite has an upper and lower motion. The instrument can be set to zero (or any angle) on a backsight then turned to a foresight and the angle is read on the plate or micrometer. Then the upper motion is left clamped and the lower motion is released and the instrument is aimed at the backsight (traditionally the telescope is reversed too), then the lower motion is clamped and the upper motion is released and the instrument is aimed at the foresight again. The angle read should theoretically be double the first reading. This was done to increase the precision of the angular measurements below the least count of the instrument. If an angle is repeated 10 times on a 1 minute transit then the angular precision is 6".

A directional theodolite does not have a lower motion, these are higher precision instruments with a least count of 1 or 2 seconds or better. Leaving the lower motion off increases the accuracy of the instrument because of less slop in moving parts. The instrument is aimed at the backsight and the angle recorded then the instrument is aimed at the foresight and the angle recorded. The angle is the difference between the two recorded readings. The multiple angle procedure employed is called set collection or turning rounds.

In starnet angles are angle right from the backsight to foresight so you have to reduce your angles to that. This is except for directional records such as the B record.

Jim Frame, post: 431965, member: 10 wrote: This is truly fundamental stuff, so a basic surveying textbook might be a better place for you to start. But basically, a direction is an angular measurement taken at a given point with respect to a known directional reference (e.g. geodetic north), while an angle is the angular quantity taken at a given point between any two other points.

Jim thank you for your response.

Your are correct this is very basic but I am neither a surveyor or an engineer, due to a series of events I have found myself in a position where by I have access to a Trimble S9 Total station but no training or guidance. I am trying to maximise this opportunity to learn while I have access to this equipment, hence the basic questions.

I now have access to the following book Elementary Surveying An Introduction to Geomatics by Charles D.Ghilani and Paul R. Wolf.

Thanks for the input.

Old time field books show stuff like this:
1 bs fd 3/4" pipe @fc
465.26' hd mag compass 21-1/2?? az
2 inst pt set 20d na 3" dp
Ang rt 47-02-30 - 2nd ang 94-05-10
191.02' hd
3 fs fd rr spk

We now have enough to start working. The compass (magnetic) orients us to the real world. The first dist is 465.26'
The doubled angle yields 1/2 of the second angle. 47-02-35
Next dist is 191.02'
This kicks off our job. On a magnetic brg.
But we continue with more precise angles, than the compass can, via ang rt.
[USER=10]@Jim Frame[/USER]. Above, is right. Get a book on elementry surveying.
It will school you well.
With diagrams.
N

Steward Souten, post: 431953, member: 12714 wrote: Hi community

I wasn't sure where exactly to place this question as it relates to StarNet and theodolites.

I was hoping someone could help shed light on the following:-

Question1

I was under the impression that there is only one type of theodolite that measures vertical and horizontal angles. However I have since been told that this is incorrect and that there are two types of theodolite, which are:-

1) Repeating theodolite
2) Direction theodolite

Can someone explain what the difference between the two are?

Question2

This came about when I was entering data into StarNet, I discovered that StarNet distinguishes between a direction and an angle when using data types such as DB, DN, DM, DE.

For the life of me I cannot figure out what the difference between a direction and an angle is in the context of StarNet.

For example I have 3 stations STN1, STN5, STN4.

I set up over STN5 which has know co-ordinates of 1000 2000 3000

I then back sight to STN1 with an azimuth of 000-00-00

I then turn clockwise to STN4 and shoot a foresight giving me a horizontal angle of 110-52-20, a slope distance of 1.120 and a zenith angle of 45-17-56.
(attached is a picture of the site)

I would normally enter these observations in StarNet as follows:-

C STN5 2000 1000 3000 ! ! !
B STN5 ƒ?? STN1 000-00-00 !
A STN5 ƒ?? STN4 110-52-20
DV STN5 ƒ?? STN4 1.120 45-17-56

For various reasons I have been told to use the directional data types of StarNet, when I do this I get the following:-

C STN5 2000 1000 3000 ! ! !
DB STN5
DN 000-00-00 !
DM STN4 1.120 45-17-56
DE

What is the difference between entering the data using C/B/A/DV and C/DB/DN/DM/DE?

I have attached the help guide extract that try's to explain what directional data types are.

I guess the fundamental point is that I don't understand the difference between a direction and an angle.

I think a simple answer to your question is that for your learning purposes it doesn't matter. As long as you do one or the other properly. Your modern total station would be classed as a direction theodolite but you can use either method to input your data.

The centring errors are applied slightly differently with each method and I have concerns with this for my work but that is a separate thread I will raise another time.

The example data lines you gave above are incomplete / incorrect

Angle input "A" needs to have an "AT" a "FROM" and a "TO". Depending on the option chosen in settings these are presented in a different order

from the manual

The "A" Code: Horizontal Angle
A At-From-To Angle

Stations defining an angle can be entered as At-From-To or From-At-To. You indicate which order you have chosen by a setting in the Project Options. You may also change the input order anytime in your data using the inline ".ORDER" option.

Example 1:

A 3-2-4 102-34-12.5

So assuming you have the default setting "At-From-To" yours would be

A STN5ƒ??STN1-STN4 110-52-20
DV STN5ƒ??STN4 1.120 45-17-56

note - no spaces between the at-from-to, just hyphens

it would be common to combine these in a M record

eg

M STN5ƒ??STN1-STN4 110-52-20 1.120 45-17-56

That is a pretty impossible slope distance and zenith angle to measure in practice but this is just for example.

You would generally need to use instrument and target heights as well. These go at the end of the line.

If you were using directions sets (can be easier when using real world observations) then your records should be

C STN5 2000 1000 3000 ! ! !
B STN5-STN1 0-00-00 !

DB STN5
DN STN1 0-00-00
DM STN4 110-52-20 1.120 45-17-56
DE

Happy learning, you are going about it a good way I think - seeing the raw data.
That is a pretty flash instrument you have to learn on. What leads you to be self-studying surveying?

If you want some real world data to examine just shout. There are also many examples provided with the program, they are probably in your DocumentsMicrosurveyStarnet folder.

James from MicroSurvey Support here,

There is an article to get people started defining their instrument settings and/or instrument Library on the MicroSurvey Support page. Just search for an article entitled: Star*Net Instrument input settings