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How to Perform 4 Basic Surveying Tasks With a Total Station

The Leica FlexLine total station.

Total stations are used wherever the positions of points or both positions and heights need to be determined. A total station consists of a theodolite with a built-in distance meter and can simultaneously measure angles and distances. Here are four basic tasks you will likely be called upon to perform with your total station.

1. Extrapolating a Straight Line

1) Position the instrument at point B.
2) Target point A, transit the telescope (i.e., reverse it) and mark point C1.
3) Turn the instrument 200 gon (180°) and target point A again.
4) Transit the telescope again and mark point C2. Point C, the mid-point between C1 and C2, corresponds exactly to the extrapolation of the line AB.

 

Extrapolating a straight line with a total station.Extrapolating a straight line with a total station.

A line-of-sight error is responsible for the discrepancy between C1 and C2. Where the line of sight is inclined, the influence of the errors is a combination of target error, tilting-axis error, and vertical-axis error.

2. Polar Stakeout of a Point

1) Set up the instrument at point A and target point B.
2) Set the horizontal circle to zero (refer to the user manual).
3) Rotate the instrument until α appears in the display.
4) Guide the reflector carrier (person) into and along the line of sight of the telescope, continually measuring the horizontal distance until point P is reached.

 

Polar stake-out of a point with a total station.Polar stakeout of a point with a total station.

The setting-out elements (angle and distance) here relate to a known point A and to a known starting direction from A to B.

3. Measuring Slopes

1) Place the instrument on a point along the straight line, the slope of which is to be determined, and position a reflector pole at a second point along that line.
2) Enter the instrument height i and the target height t (prism). The vertical angle    reading in gon or degrees can be set to % (refer to the user manual for your total station model) so that the slope can be read off directly in %.
3) Target the center of the prism and measure the distance. The slope is shown on the display in %.

 

Measuring slopes with a total station.Measuring slopes with a total station.

 
4. Plumbing Up or Down

Plumbing down from a height point, plumbing up from a ground point, and inspecting a vertical line on a structure can be carried out accurately in just one telescope face, but only if the telescope describes a precisely vertical plane when it is moved up and down. To make sure this occurs, proceed as follows:

1) Target a high point A, then tilt the telescope down and mark the ground point B.
2) Transit the telescope and repeat step 1 in the second face. Mark point C.
3) The mid-point between B and C is the exact plumbing point.

 

Plumbing up or down with a total station.Plumbing up or down with a total station.

If these two points do not coincide, you may have encountered a tilting-axis error and/or an inclined vertical axis. To minimize the influence of vertical-axis tilt on steep sites, be sure to level your total station precisely before beginning your work.

 
Now that you’re familiar with the basics, you may want to practice on your own. If you don’t have access to your own total station or tripod, consider renting some gear or consulting with our knowledgeable staff. Allen Precision also boasts a 5000-square-foot training center and store if you prefer to try before you buy.