Levelling A & B Flashcards
Flat
- to put on the same plane
- not always level
Level
-to put on the same plane as the horizon
Plumb
- to align perpendicular to the horizon (vertical)
- think of a “plumb bob”
Straight
-to be in direct line of (straightness)
Square
-something aligned 90 degrees to a reference line
Refraction
-light bends differently and travels at different speeds through different materials
Diffraction
-shooting close to an edge can cause light to bend
Vibration
-can travel through the stand and cause the target to appear blurred
Pentaprisms
- 5 sided prism
- regardless of the angle at which the incident ray enters, the refracted Ray leaves at exactly 90 degrees
- the image is not reversed
Source of error
-rays can become distorted through a change in temperature, through glass (reflection and refraction)
Optical micrometer
- used for precision levelling to .001”
- it’s parallel lens has the ability to bend the light rays and send them out again exactly parallel to the original line of sight.
Coincidence level
- used with tilting level for bucking in.
- bubbles fold onto itself
Lenses & Prisms
- light can be reflected on a polished surface with the angle of incidence being equal to the angle of reflection
- in thinner material to thicker material the light always refracts towards normal
Optical lines of sight
- used instead of a tight wire or string line
- doesn’t sag, get kinked, vibrate
Auto-reflection
- auto means mirror (target)
- uses a mirror to send a target image on the crosshairs back to the telescope (2 units working together)
- when you see the reflected image you see the telescopes own crosshairs in the reflected image in the target.
- problems with it are the possible incident rays and the mirror may be tilted.
Auto-collimation
- auto means mirror, Collimation means light
- most accurate because it’s aimed at the reflected image of the crosshairs of the telescope itself.
- sees one set of crosshairs when the object of 90 degrees
Collimation
- no mirror, two telescopes or one and a Collimator
- projects crosshairs of one telescope onto the crosshairs of the other telescope or Collimator both focused at infinity
Collimator
-no eye piece, used for Collimation instead of a second telescope
Optical Squares
- mounted on a telescope and establishes a plane perpendicular to the reference line of sight
- the pentaprism is the basis of this tool which allows the line of sight to change 90 degrees
Rough alignment scales
- used for levelling floors and setting the grade for drainage pipes.
- accurately read to the closest 1/2 centimetre
Obtaining an accurate reading?
-waving the rod and then take the shortest reading
Precision scales
-accurate up to .001”
Alignment bar
- can measure over 100ft like rollers on a conveyor
- accurate up to .001”
Alignment telescope
- most accurate for establishing a straight lie of sight
- can do this by using an optical square, coincidence sliding level and a special plumb aligner bracket