Angles III

Question 1

What do modern day surveying instruments have in them? (2)

Answer 1

1) They are packed with electronics
2) In a total station you get a lot more functionality than a classic theodolite, e.g. graphical interfaces, SD card slot etc.

Question 2

What were in 1970’s and 1980’s surveying instruments? (3)

Answer 2

1) No electronics
2) Has a horizontal and vertical glass circle
3) Had to look through a second telescope and open a little window which allows for an optical train of prisms carries light through the instrument, through the glass circle into your eye.

Question 3

What are the diameters of the modern total station circles?

Answer 3

Rarely >150mm diameter and 70mm diameter are common.

Question 4

What is it difficult to divide?

Answer 4

The circumference into 1’’ or smaller intervals.

Question 5

Example: d=150mm, what would be spacing required between 1-minute divisions?

Answer 5

1/50mm= 0.02mm

Question 6

What is the circumference of a circle divided into?

Answer 6

30’,20’ or 10’ intervals + additional reading system to allow for more accurate readings.

Question 7

What are the graduation on optical class circles for optical glass circle?

Answer 7

Photographically etched on glass.

Question 8

What does Optical Reading System and optical micrometre?

Answer 8

Accurate readings.

Question 9

Describe optical glass circles.

Answer 9

Image of a circle is brought alongside the main telescope.

Question 10

Describe optical circle reading system.

Answer 10

Here the user see a glass scale, graduated over 1 division of the glass circle e.g. 10’, 20’ or 30’ of arc are common. The glass scale is superimposed over the main scale graduation cuts the optical scale.

Question 11

What does the Optical circle reading system give a resolution of at best?

Answer 11

20-30’’

Question 12

What is an optical micrometre?

Answer 12

It is often a parallel sided plate of glass used to display the main circle graduation until one of these coincides with an index mark.

Question 13

What are the two types of optical micrometre?

Answer 13

1) Single reading

2) Double reading

Question 14

What is the resolution if a single sided reading?

Answer 14

6’’

Question 15

What are the circles made from in TS and theodolites?

Answer 15

They are made from glass but read electronically.

Question 16

What is done to the circle that is inside a TS and theodolite?

Answer 16

It is electronically coded and can be read automatically.

Question 17

What are the two encoding systems used?

Answer 17

Absolute and incremental encoding.

Question 18

What are the advantages of electronic circle reading? (2)

Answer 18

1) Read errors greatly reduced

2) Speed of operation increased

Question 19

What are the similarities between TS and theodolites? (2)

Answer 19

1) Both have tribrach and foot screws

2) Horizontal glass circle + bubble +clamp and slow-motion drive.

Question 20

What are the differences between TS and theodolites? (3)

Answer 20

1) Simpler optics, more electronics
2) Circles read electronically
3) No reading optics, no micrometre

Question 21

What are the characteristics of TS? (4)

Answer 21

1) Built-in processing routines
2) Slope to horizontal distance
3) Resection
4) Traversing

Question 22

What are the internal computations (error correction) inside TS? (3)

Answer 22

1) Can increase accuracy of instrument if able to detect and correct error
2) For more precise work we still take FL and FR observations
3) Correction based on technique called axis compensation.