Theodolite - Measuring Angles

Summary

This instructional script details the setup and use of a theodolite for precise angle measurements in surveying. It covers tripod leveling, theodolite mounting, and bubble level adjustments for accuracy. The tutorial explains the use of adjustment knobs for both vertical and horizontal axes, recording angles in face left and right modes to ensure calibration, and focusing techniques to minimize parallax. It also describes the use of an optical plummet for aligning the instrument over a specific point and measuring distances between surveying stations.

Takeaways

• 🧰 Once the tripod is level, attach the theodolite using the locking screw, ensuring it's finger tight.
• 🔧 Use the three adjustment screws to center the bullseye level, adjusting two screws together and the third separately.
• 📐 The theodolite has a secondary bubble level for higher accuracy; align it within the markers by turning the instrument 90 degrees and repeating the adjustment.
• 🔍 The theodolite includes an eyepiece, sight, focus rings, and several adjustment knobs for precise targeting and measurement.
• 🔒 The vertical and horizontal adjustment knobs have locks that must be engaged for fine adjustments to work.
• 🔢 For angle measurement, use face left and face right modes to eliminate calibration issues by averaging measurements from both modes.
• 🔭 Focus the crosshairs through the eyepiece using a piece of paper to ensure sharpness and reduce parallax.
• 🎯 Use the sight on top of the instrument for initial targeting, then fine-tune through the eyepiece with horizontal and vertical locks applied.
• 📏 Record horizontal angles on the booking sheet, starting with zeroing the instrument and recording measurements at different targets.
• 📊 Average the face left and face right measurements to calculate the final angle for further calculations.

Q & A

What is the first step in setting up a theodolite?

The first step is to ensure the tripod is level, then place the theodolite on top of the tripod using the locking screw, making sure it is finger tight but not over-tightened.

How do you adjust the bullseye level on a theodolite?

Use the three adjustment screws to bring the bullseye level into the center circle. Two screws are used together to move the bubble in or out, and the single screw is used to center the bubble directly.

What is the purpose of the secondary bubble level on the theodolite?

The secondary bubble level is set to a higher degree of accuracy and is used to ensure the instrument is set up correctly for precise measurements.

How do you ensure the secondary bubble level is correctly aligned?

Adjust the instrument using the two adjustment screws until the bubble is between the two markers. Then, turn the instrument 90 degrees and repeat the procedure using the single adjustment screw.

What are the functions of the adjustment knobs on the eyepiece of a theodolite?

The adjustment knobs on the eyepiece are used for focusing the crosshairs and adjusting the vertical and horizontal angles of the theodolite.

Why is it necessary to lock the vertical adjustment before making fine adjustments?

The vertical lock prevents the instrument from moving in a vertical manner, allowing for precise targeting of the prism and accurate angle measurements.

What is the significance of using both face left and face right modes when measuring angles with a theodolite?

Using both modes helps eliminate any calibration issues with the instrument by measuring the same angle from two different orientations.

How do you reduce parallax when using a theodolite?

Hold an A4 page in front of the lens and adjust the focus on the eyepiece back and forth until the crosshairs are sharp and in focus.

What is the purpose of the optical plummet on a theodolite?

The optical plummet allows the user to see a point on the ground directly beneath the prism, useful for setting up over a known surveying point or measuring distances between two points.

How do you record angles in a booking sheet when using a theodolite?

Record the angles in a U-shape pattern, making two measurements for each angle in both face left and face right modes. Calculate the average of the two measurements for each angle to use in further calculations.

What is the process for measuring the distance between two points using a theodolite's optical plummet?

Align the optical plummet with a known point, have a colleague mark the point on the ground, repeat at a second station, and then measure the distance between the two marked points using a tape measure.

Outlines

00:00

📐 Setting Up Theodolite and Leveling

This paragraph details the initial setup of a theodolite for surveying. It begins with leveling the tripod and securing the theodolite using a locking screw. The focus is on aligning the bullseye level to the center circle using adjustment screws, ensuring the bubble is centered for a rough measurement of the instrument's horizontal alignment. A secondary, more accurate bubble level is also discussed, which must be correctly aligned between two markers for precise measurements. The paragraph also describes the components of the digital theodolite, including the eyepiece lens, adjustment knobs, and focus rings for crosshairs and distance.

05:01

🔧 Adjusting and Locking Theodolite for Precision

This section explains the process of adjusting and locking the theodolite for precise angle measurements. It covers the use of vertical and horizontal adjustment knobs, which include inner rings for locking the instrument in place and fine adjustment knobs for targeting the prism. The importance of applying the horizontal lock before making fine adjustments is emphasized. The paragraph also describes the theodolite's digital display, optical plummet, and the method of recording angles in both 'face left' and 'face right' modes to account for any calibration issues, ensuring accurate measurements.

10:02

🎯 Targeting and Recording Angles with Theodolite

The paragraph outlines the procedure for targeting and recording angles using a theodolite. It starts with removing horizontal and vertical locks to use the site on top of the instrument to aim at the target. Once the target is aligned, locks are applied, and the eyepiece is used to focus on the object and adjust the crosshairs. The process of setting the zero angle and recording the first angle is explained, followed by rotating the instrument 180 degrees to record the angle in a 'face right' mode. The importance of using both modes to eliminate calibration errors is highlighted.

15:05

📊 Recording and Calculating Angles in Surveying

This section delves into the recording of angles in a booking sheet and the process of calculating the average of multiple angle measurements. It describes the initial setup of the theodolite, the recording of angles to two different targets, and the method of calculating the difference between two face left and two face right measurements. The average of these differences is used for further calculations, ensuring the accuracy of the surveying data.

20:06

🌐 Utilizing Optical Plumber and Distance Measurement Techniques

The final paragraph discusses the use of the optical plummet for precise point targeting and the method of measuring distances between two surveying points. It explains how to align the instrument over a known point using the optical plummet's focus and target. The technique of using a colleague to mark a point on the ground and measuring the distance between two such points using a measuring tape is also covered, providing a comprehensive guide to distance measurement in surveying.

Keywords

💡Theodolite

A theodolite is a precision optical instrument used in surveying for measuring angles in the horizontal and vertical planes. In the video, it is the central tool being set up and used to measure angles and distances accurately. The script describes the process of mounting the theodolite on a tripod and leveling it using adjustment screws.

💡Tripod

A tripod is a three-legged stand used to support the theodolite at a stable height and angle. The script mentions leveling the tripod before mounting the theodolite, emphasizing the importance of a stable and level base for accurate measurements.

💡Leveling

Leveling refers to the process of adjusting an instrument to a true horizontal or vertical position. The script details the use of the theodolite's adjustment screws and bubble levels to achieve a level state, which is crucial for accurate angle measurements.

💡Bullseye Level

The bullseye level is a circular level with a central bubble used to indicate when the theodolite is level. The script describes using the bullseye level to center the bubble, providing a visual aid for initial leveling before more precise adjustments are made.

💡Adjustment Screws

Adjustment screws are used to fine-tune the position of the theodolite's components to achieve the desired angle or level. The script mentions using these screws to align the bullseye level and the secondary bubble level, ensuring the instrument's accuracy.

💡Spirit Level

A spirit level, also known as a bubble level, is a tool with a bubble that indicates the levelness of an object. The script refers to a secondary spirit level on the theodolite for higher accuracy, which must be aligned between two markers for proper setup.

💡Optical Plummet

An optical plummet is a device used to align the theodolite directly over a specific point on the ground. The script describes its use for setting up over a pin or measuring distances between two points, highlighting its role in precise positioning.

💡Crosshairs

Crosshairs are the intersecting lines in the eyepiece of the theodolite that help in targeting a specific point. The script mentions adjusting the focus of the crosshairs to reduce parallax and ensure sharp targeting of the prism.

💡Prism

A prism is a reflective target used in surveying to reflect the theodolite's sight back to the instrument, allowing for accurate angle measurements. The script discusses targeting the prism for angle measurements and using it for distance measurements with the optical plummet.

💡Face Left/Right Mode

Face left/right mode refers to the orientation of the theodolite's measurement part relative to the operator. The script explains that measurements are taken first in face left mode and then repeated in face right mode to account for any calibration issues and ensure accuracy.

💡Booking Sheet

A booking sheet is a record of the measurements taken during a survey. The script describes how to fill out the booking sheet with the angles measured from different orientations (face left and face right) and how to calculate the average angle for further use.

Highlights

Setting up a theodolite involves leveling the tripod and securing the theodolite with a locking screw.

Adjustment screws are used to center the bullseye level and align the bubble within the circle for accurate leveling.

A secondary, more accurate bubble level on the theodolite requires alignment between two markers for precise measurements.

The theodolite's eyepiece includes a focus ring for adjusting the visibility of crosshairs.

Vertical and horizontal adjustment knobs allow for precise targeting of a prism or surveying point.

Locks are essential for securing the theodolite's position before making fine adjustments.

Digital display and optical plummet are integral parts of a theodolite for angle measurement and alignment.

Two measurement modes, face left and face right, are used to eliminate calibration issues in angle recording.

Parallax error is minimized by using a sharp focus on crosshairs, demonstrated by focusing on an A4 page.

The sighting method involves using a white triangle to aim at the target before locking and adjusting through the eyepiece.

Zero angle setting is crucial for accurate angle measurements, demonstrated by a double press of the zero angle button.

Recording angles involves targeting objects, using fine adjustments, and noting measurements on a booking sheet.

The booking sheet records angles in a U-shape pattern, allowing for the calculation of average angles for accuracy.

The optical plummet is used for aligning the theodolite directly over a known surveying point on the ground.

Focus adjustment is necessary for the optical plummet to ensure clear visibility of the target circle and dot.

Measuring the distance between two stations involves using the theodolite's plummet and a measuring tape.

The process of setting up and using a theodolite is critical for accurate surveying and construction projects.

Transcripts

once our tripod is level

we're going to take the theodolite from

the box and offer it up to the

top of the tripod again using the

locking screw

to hold it into place

remember the lock and screw is to be

finger tight and not to

over tighten it now

we're going to try and use the three

adjustment screws to bring

the bullseye level into

the center circle so remember using

these screws

these two screws in together are out

together

to bring the bullseye level into

the center and then

using the single screw to bring the

bubble

directly into the center

so again using the two adjustment screws

in together

right together with thumbs to bring the

bubble in line with the circle of the

bullseye level

then using the single adjustment screw

to bring the bubble into the center

of the bullseye level

on the theodolite we have our bullseye

level and that's

set up correctly but we also have a

secondary

bubble level here on the instrument

itself

this second one is set up to a higher

degree of accuracy

so the bubble bullseye level down here

is kind of a rougher

course measurement for how horizontal or

flat the instrument is set up at

here this instrument this spirit level

uh bubble level here is set to a higher

degree of accuracy

for us to use this instrument correctly

this

bubble level must be set correctly in

between

the two markers to do that

again you align the instrument up with

the two adjustment screws that you're

using

and either in together or out together

move the adjustment screws in this case

by a small amount

because the bubble level is nearly

correct

so that the bubble is in between

the two markers

once the spirit level spurt bubble

is within the two markers we turn the

instrument

90 degrees

and we repeat the procedure for getting

this bubble

within the two markers but this time

we're just going to use

the single adjustment screw

so no matter where we turn the

instrument it should be

the bubble should be it should be in

between the two markers

just check at several locations

given the bubble

level time to respond

checking it at several points

nine instrument is set up ready to be

used

to describe the elements of our digital

theodolite

we have an eyepiece

lens we have a site

on top of the optic and we have

a number of adjustment knobs on the

eyepiece

we have a focus ring for the crosshairs

on the actual body of the

optical lens we have a distance focus

ring so whenever you're looking at your

target you'll bring it into focus

using the adjustment of this ring here

we have a number of adjustment knobs

this is a

vertical adjustment here it comprises

two parts

the inner ring will lock

the instrument so it cannot be moved in

a vertical

manner and you can rotate it up and down

with the lock applied on you can no

longer move it

and then with the inner adjustment knob

you can

move the eyepiece

up and down by small amount so you can

target

your prism

exactly likewise

this is the adjustment knob or the lock

and the adjustment knob for the vertical

axis

turn it around here we have the

adjustment knob

for the horizontal axis so

they apply the lock so the instrument

can no longer

be turned around apply it on

and then you can use the second

adjustment

knob to rotate the instrument by a small

horizontal angle

note for these fine adjusts for the

horizontal

and for the vertical angle

they will not function unless the

horizontal lock

is actually applied so with the

horizontal lock off the spine adjust

doesn't have any effect the lock has to

be applied first

before the any adjustment will actually

take place we have our

bullseye level digital display

here we have an optical plummet

so looking through this eyepiece

we will actually see a point on the

ground

directly beneath the prism

the theodolite like a total station has

two ways to

record angles what i mean by that either

face left or face right

initially we take angle measurements in

the face left mode

what i mean by that is face left

looking through the eyepiece where is

the

measurement part of the instrument the

measuring part of the instrument

is this side here or an easier way

to describe it is the battery pack

upgrade pack this is the battery pack so

wherever the battery pack

is the measurement side of the

instrument

is on the other side this case looking

through the eyepiece

the measurement part of the instrument

is on the

on the left we're recording this angle

when we look through our target

looking at the prism recording the angle

in a face left mode

we will then turn to target

our second present and record

the angle

once the angle has been recorded we'll

then flip

the instrument turn it 180 degrees

turn the eyepiece 180 degrees so we

target back at the

same seconds target now

the measurement part of the instrument

is on the right hand side so now we are

recording the angle in the face right

mode

target the prism record the angle turn

back

to where we initially were and target

the prism in this case and record the

angle

again this is in a face right angle

then we go to our booking sheet we can

work out the difference between the two

angles and

take an average the reason for doing

this

is that if there is any calibration

issues with the instrument

by measuring it face left

and then subsequently measuring the same

angle

but now in a face right mode

angle there back to there any

calibration issues

will be eliminated

so that we're using this one correctly

we need to have

the cross hairs that you see through the

eyepiece and sharp focus

this is to reduce parallax so you take

a plane a4 page hold it

in front of the lens and

with the focus on the eyepiece we adjust

it back and forth

until the crosshairs are nice and sharp

with the horizontal and the vertical

locks removed

we're going to use the site on top of

the instrument

to target or point towards the target

that we are using

so looking through the target remotely

you'll see a little white triangle and

we're going to aim the point of the

triangle

towards the target that we are using in

this case

it is the center of the prism then we

can

apply the horizontal and

vertical locks and then move to look

through

the eyepiece

looking through the eyepiece we can use

the distance focus string

to bring the object into focus

and then use the horizontal

and the vertical flame adjust

to bring the prism

into line

with the target

back to our display and we can then

set our zero angle so a double press

of the zero z angle we set the

horizontal angle

to zero removing the vertical

and horizontal locks we can then

move the instrument to target our second

object

using the site again to line it up

before you look through the eyepiece

apply the horizontal and vertical locks

and then look through the eyepiece and

use the fine adjusts

to bring it exactly into the center of

our second target

in this case it's going to be a second

prism

looking through the eyepiece

looking through the eyepiece using the

distance focus

we can bring our object into

focus and they are using the

line adjusts we can move the crosshairs

so that in this case it is exactly

in the center of the prism

looking back at the display we can

record our first angle

of being 38 degrees

43 minutes and 50 seconds

this first angle was record as recorded

and a face left left manner

remember the measurement part of the

instrument is on the left hand side

the battery being on the right with the

angle recorded

remove the vertical and horizontal locks

rotate the instrument 180 degrees rotate

the eyepiece

180 degrees targets

back on the original object

using the site

to line you up

approximately apply the

horizontal

apply the horizontal and the

vertical locks we can then look through

the eyepiece

and target the

prism exactly using the distance focus

we can bring the prism directly into

view

and then using the fine adjust

we can move the crosshair

you can move the crosshairs exactly in

the center of the target

the way the instrument is set up the

measurement part of the instrument is on

the right hand side

and then we can go and record the third

angle

third horizontal angle 118

degrees 43 20.

and then we're going to go back

remove the horizontal and vertical locks

go back and target the initial

present in this case

we use the site initially

to get it lined up so you're pointing in

the right direction

once you're pointing approximately in

the right direction

you apply the horizontal

and the vertical locks then you can look

through the eyepiece

and then use the fine adjusts

to bring the crosshairs onto the target

exactly

using the distance focus we bring our

target

into focus the center of the prism then

using the fine adjust

we can move the crosshair target

into the exact center of the prism

then we can record the final angle

which is 170 degrees

58 minutes 30 seconds

when we are doing our measurements there

is a way for us

to actually record the angles into a

booking sheet

initially when we set up our theodolite

at point a we looked at the prism

at point b and targeted the theodolite

to prison b we would say when we fill in

the booking sheet our instrument is at

point station a and we observed

our target at station b

we zero to the satellite and here we

record an

angle of zero minutes zero

zero degrees zero minutes zero seconds

the theodolite was then rotated

clockwise

and targeted on our second target

prism

c

and the horizontal angle recorded

when we did that that gave us an angle

of

38 degrees 27

minutes and 0 seconds

both measurements to start off with were

done with the

instrument and face left mode

the theodolite was then rotated around

180 degrees and the eyepiece rotated

so that you are now looking back at

prism

c but the instrument

was in a face right mode

angle recorded in that situation

was 318 degrees

27 minutes

20 seconds the

light was then rotated back to

prism b and the horizontal angle

recorded

that was 180 degrees

14 minutes and 30

seconds so when filling in

part of the booking table we fill it in

first we do our two face left

measurements

zero it rotate

and record the angle flip it around

just face right record the angle

back to the original target record the

angle

so you're filming in the angles

and like a u-shape and the four cells

to do calculations with the angles which

angle we actually use because we've

actually measured the angle twice

we take the difference between the two

face left measurements

and write it in the red box so the

difference between

38 27 0 and 0

gives you 38 degrees 27

minutes zero seconds

doing the same with the two face right

measurements difference between 218

27 20 180 1450

the difference there is 20. there are 38

12 30.

you can see the two angles are

reasonably similar

but the angle we'd use in further

calculations is the average

of these two angles so type in your 27

20 38 27 0 add to that

the 38 12 30

and together divided by two and the

average of those two angles

is 38 degrees 19

minutes 45 seconds and

this is the angle that would be used

in further calculations

on the side of the strip instrument is

the optical plummet

so here with the optical plummet you

will look with your i3 here

and with a present in the body of the

instrument

prism in here it will then enable you to

look

directly beneath the instrument

through the locking screw to a point on

the ground

that is directly underneath the

instrument

this is used whenever you're trying to

set up over a pin or you're trying to

get a distance measurement between

two points

two rings this ring doesn't move doesn't

adjust

anything this ring here will bring this

site

that you see when you look through the

eyepiece into focus

previously we've used a crosshair as our

target

in this plummet we have a circle with a

dot in the center so it's a slightly

different type of target

this adjustment ring on the outside is

used to bring

the focus ring

and the target circuit dot into

focus whenever you're looking through it

here you can see the circular ring and

the

dot in the center and the dot in the

center a sort of small ring in the

center

is used to align the instrument directly

over a known point or surveying point in

the ground

for our measurements we want to know

where i want to measure the

distance between two stations so

one way to do it is to take your foot

and to

gradually reduce or move your foot back

until your top of your toe is

at the

center of the inner ring

and then a colleague can mark that point

and on the ground

with a piece of chalk using a tip

measure

we can then repeat that at a second

station

and use a 50 meter tip measure to

measure the distance between the two

stations