A total station can be used for surveying, but it will only do what you tell it to. That’s why accurate measurements depend on the right setup. Most total stations measure angles with the electrical-optical scanning of precise bar codes that are etched onto rotating glass cylinders or discs located inside the device. The best total stations can measure angles to 0.5 arc-seconds, but “construction grade” models that are less expensive can measure angles to 5 or 10 arc-seconds.
How to Set Up a Total Station for Measuring
Like any other piece of survey equipment, a total station needs to be set up properly before it can measure accurately. You want to start with a point that you have already measured, and enter the station’s coordinates and orientation. Here are the steps on how you can do this properly:
- Place your tripod close to where your ground point is located.
- Inspect the tripod at various angles, and move it until the plate is positioned horizontally above the ground point.
- Push the tripod’s legs firmly into the ground, and secure it in place with the central fixing screw.
- Turn on the laser plummet (or optical plummet on older models), and turn the foot screws so it’s in aligned with the ground point.
- Center the bulls-eye bubble by adjusting the length of the tripod’s legs.
- Move the total station on the tripod plate until the laser dot is precisely centered over the ground point.
- Enter the station’s coordinates according to the instructions provided in the user manual.
- Once you’ve completed these steps, aim at another known point and enter the coordinates or horizontal angle.
Once you have set up the device, you’ll be able to stake out coordinates or measure other points within that coordinate system.
How to Use a Total Station for Staking Out Points
Once it has been properly calibrated, you can use the total station to stake out points. Here is how to use a total station for this type of action:
- Position the device at a known point by setting the horizontal circle.
- Enter the coordinates of the point that you want to stake out (which the device should do automatically).
- Move the device until the horizontal circle reads zero.
- Position the reflector so it points to the same location (point P).
- Measure its distance by calculating the difference between the distance D to the point P (which should be done automatically).
The coordinates of each point you want to measure can be transferred from your computer to the survey equipment you’re using. That way, all you have to do is select the point number you want to measure. And if two of them are known, you can use the resection method to calibrate the device.