How to Orient a Total Station?

Backsighting (Orientation) is the process of telling the instrument its position. 
Orientation means telling the Total Station "which direction it is facing" so that all its angle and distance measurements match the real-world coordinates (North, East, Elevation) of a point.

Why do we need orientation?

When we set up the total station on a point, it knows:
• Its own position (if we entered coordinates), and
• How much it turns left/right and up/down.
But it doesn’t know which way is North or where the other points are located in the actual world. Orientation fixes this problem.

If we skip this or do it incorrectly, every single point we shoot afterward will be wrong.

Here is the step-by-step, field-proven guide to perform a backsight orientation.

Orientation can be done in 3 ways.

1. Orientation using a backsight point
2. Orientation using a known bearing
3. Orientation by resection method

1) Orientation using a backsight point

This Method is used when we know the data (coordinates) of the instrument station and also the coordinates of an another point on ground.

Steps:
- First, Set up the TS exactly over a point (Say A) of which coordinates are known. (Set up Includes set up tripod, mounting TS, Levelling and Centering)
- Turn on the TS,  and Open Orientation/Backsighting menu.
- Enter instrument station (Occupy Station) coordinates (N,E,Z), Point ID and height of instrument.
 - Enter Backsight Point Coordinates (N,E,Z) of another known point (Say B). Also enter Point ID and Prism's height for that point. The instrument will internally calculate horizontal angle (azimuth) between A and B.
- Place a prism at B (or without prism) and Look through the telescope and aim the crosshairs exactly at the center of the prism/target.
- Press 'Measure'
- Press 'Set'
The instrument is now oriented!
Alternatively, This can also be done directly when taking field data using the 'New Job' or 'Create Job' menu. (There will be options, namely  Occupy Station, Backsight and Take data inside 'New Job')

2) Orientation using a known bearing

This Method is used when we know the data (coordinates) of the instrument station  and the  azimuth/bearing of a line/ point on ground.

Steps:
 - First, Set up the TS exactly over a point (Say A) of which coordinates are known. (Includes set up tripod, mounting TS, Levelling and Centering)
- Turn on the TS,  and Open Orientation/Backsighting menu.
- Enter instrument station (Occupy Station) coordinates (N,E,Z), Point ID and height of instrument.
- Go to Set Azimuth or Set Bearing.
- Enter azimuth angle of a known line/ point (Say B).  Example: If the azimuth from A to B is 127°30'45", enter that value. 
- Place a prism at B (or without prism) and Look through the eyepiece and aim the crosshairs exactly at the center of the prism/target.
- Press 'Measure'
- Press 'Set'
- The instrument will internally calculate the (N,E,Z) of point B.
The instrument is now oriented!

3) Orientation by resection method

Resection/Free Stationing method is adopted when we cannot set up TS on a known point, so we set up TS anywhere at convenient place (at any unknown point) and at least 2 (3 points for more precision) known points are visible from the instrument station.

Steps: 
- Set up the TS at any  unknown point (let's call it point P).
- Turn on the TS and open Resection/Free stationing program  menu.
(This varies by TS brand. So look for: 
Program→ Resection
Survey→ Resection
Station Setup→ Resection
Coordinate→ Resection)

- Enter coordinates of the first known point (Say A) , aim that point through the telescope and press measure to record that point.
- Enter coordinates of the second Known Point (Say B) , aim that point through the telescope and press measure to record that point.
- Similarly, We can also enter coordinates of other known points (Points  C, D,...) for greater accuracy. But at least 2 point's coordinates are necessary. The more known points we measure to, the more accurate our orientation will be.
- Now The Total Station automatically calculates the coordinates of Point P and azimuth angle.