Angles III Flashcards
What do modern day surveying instruments have in them? (2)
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.
What were in 1970’s and 1980’s surveying instruments? (3)
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.
What are the diameters of the modern total station circles?
Rarely >150mm diameter and 70mm diameter are common.
What is it difficult to divide?
The circumference into 1’’ or smaller intervals.
Example: d=150mm, what would be spacing required between 1-minute divisions?
1/50mm= 0.02mm
What is the circumference of a circle divided into?
30’,20’ or 10’ intervals + additional reading system to allow for more accurate readings.
What are the graduation on optical class circles for optical glass circle?
Photographically etched on glass.
What does Optical Reading System and optical micrometre?
Accurate readings.
Describe optical glass circles.
Image of a circle is brought alongside the main telescope.
Describe optical circle reading system.
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.
What does the Optical circle reading system give a resolution of at best?
20-30’’
What is an optical micrometre?
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.
What are the two types of optical micrometre?
1) Single reading
2) Double reading
What is the resolution if a single sided reading?
6’’
What are the circles made from in TS and theodolites?
They are made from glass but read electronically.
What is done to the circle that is inside a TS and theodolite?
It is electronically coded and can be read automatically.
What are the two encoding systems used?
Absolute and incremental encoding.
What are the advantages of electronic circle reading? (2)
1) Read errors greatly reduced
2) Speed of operation increased
What are the similarities between TS and theodolites? (2)
1) Both have tribrach and foot screws
2) Horizontal glass circle + bubble +clamp and slow-motion drive.
What are the differences between TS and theodolites? (3)
1) Simpler optics, more electronics
2) Circles read electronically
3) No reading optics, no micrometre
What are the characteristics of TS? (4)
1) Built-in processing routines
2) Slope to horizontal distance
3) Resection
4) Traversing
What are the internal computations (error correction) inside TS? (3)
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.
