Test: Total station - Civil Engineering (CE) MCQ

The 3 types are microwave (Tellurometer), infrared (Distomat) and visible range (Geodimeter).

Total Station

• A total station, also known as an electronic tachometer, is an optical instrument.
• It is a combination of an electronic theodolite for measuring horizontal and vertical angles,
• An electromagnetic distance measurement (EDM) device for measurement of slop distances, and onboard software to convert the raw observed data to three-dimensional coordinates.
• Thus with a total station, one may determine the actual positions (X, Y, and Z ) or northing, easting, and elevation of surveyed points or the position of the instrument from known points in absolute terms.
• Further, the EDM that measures the slop distance can calculate and display horizontal distance and difference in level.
• This is accomplished with the help of a microprocessor normally working concentric with the telescope eyepiece and generally housed in a casting that forms part of the telescope.

Uses of Total Station

• It is a combination of electronic theodolite for measuring horizontal and vertical angles.
• Distance between any two points and Elevation of objects can be measured. 
• All three coordinates of the observed points can be measured.

Total Station:

• Total station is a combination of an electronic theodolite and an electronic distance meter (EDM).
• The combination makes it possible to determine the coordinates of a reflector by aligning the instrument cross-hairs on the reflector.
• A microprocessor in the instrument take care of the recordings, readings, and other computations.

Uses of Total Station

• It is a combination of electronic theodolite for measuring horizontal and vertical angles.
• Distance between any two points and Elevation of objects can be measured. 
• All three coordinates of the observed points can be measured.

Total Station

• Total station is a combination of an electronic theodolite and an electronic distance meter (EDM).
• The combination makes it possible to determine the coordinates of a reflector by aligning the instrument cross-hairs on the reflector.

Uses of Total Station

• It is a combination of electronic theodolite for measuring horizontal and vertical angles.
• Distance between any two points and Elevation of objects can be measured. 

​​​​​​​Parts involved in the total station

• Tripod setup
  • Tripod legs should be equally spaced and the tripod head should be approximately leveled and should be above the survey point.
• Mounting instrument on a tripod
  • Place Instrument on Tripod Secure with centering screw while bracing the instrument with the other hand.
• Focus on the survey point
  • Focus the optical plummet on the survey point
• Levelling the instrument
  • Adjust the leveling foot screws to center the survey point in the optical plummet reticle.
  • Center the bubble at the circular level by adjusting the tripod legs Loosen the horizontal clamp and turn the instrument until plate level is parallel to 2 of the leveling foot screws.
  • Center the bubble using the leveling screws- the bubble moves toward the screw that is turned clockwise.
  • After re-tightening the centering screw check to make sure the plate level bubble is level in several.
• Adjust image and article focus
  • Release the horizontal & vertical clamps and point a telescope to a featureless light background.
  • Adjust the reticle (i.e. cross-hair) focus adjustment until the reticle image is sharply focused. Point telescope to target and adjust the focus ring until the target is focused.
• Measuring the height of the object
  • Level the instrument at a site where the target can be viewed through the telescope and the mirror target can be set up directly below the target.

Total Station:

• A total station is an electronic/optical instrument used in modern surveying and building construction that uses electronic transit theodolite in conjunction with an electronic distance meter (EDM).
  

Figure: Total Station

• It is also integrated with a microprocessor, electronic data collector, and storage system.
• It is a combination of an electronic theodolite for measuring horizontal and vertical angles, an electromagnetic distance measurement (EDM) device for measurement of slop distances, and onboard software to convert the raw observed data to three-dimensional coordinates.

Hence, Total Station can directly be used to calculate - Horizontal angles, Vertical angles, and Sloping distances.

Temporary Adjustments of Total station
Adjustments which required to be made at every instrument station before making any observation. It can be done by following three procedures,

• Centering the Total station over the station.
• Levelling the Total station.
• Elimination of parallax.

​Centering the Total station over the station

• This includes the Centering of the Total station over the ground mark and also approximate levelling with the help of Tripod legs.
• While centering, it is necessary to ensure the approximate levelness; otherwise, the centering will be disturbed when subsequent Levelling of the instrument is done. It can be done either using a plumb-bob or laser plummet.

Levelling the Total station
Accurate Levelling is done with the help of plate levels using levelling screws. Here the Vertical axis (plumb line)of the Total station is made truly vertical.

• Align the bubble parallel to two-foot screws and bring it to the center by turning both screws same direction.
• Align the bubble with the remaining foot screw (turn 90°) and bring it to the center by rotating it
• Repeat the process till the bubble remain centered in any direction. Principle of reversibility.

Elimination of parallax

• It is done by focusing the eyepiece for the distinct vision of crosshairs and focusing on the object to bring the image of the object in the plane of crosshairs. Accurate bisection and sighting are difficult when there is Parallax.
• Hold a white paper in front of the objective or sight the telescope towards the sky. Move the eyepiece in or out till the crosshairs are seen as sharp and distinct.
• Can be checked by moving the eye slowly to one side. If there is no parallax the image and the crosshairs will appears still.

Microwave EDMs can be used up to a range of 100km to locate the object. Infrared is a commonly used type, with a range up to 3km.

Total station can be used to measure distance and angles. It employs an electronic theodolite and an EDM to serve this purpose.

Microprocessor is the unit that processes the data collected and uses it to compute various features like horizontal and vertical distances, slopes, elevation, etc.

Total station is affixed on to the tripod. The legs of the tripod are extended/contracted one by one till the bubble is centralised.