Theodolite v/s Total Station

These are two of the main surveying instruments that are used for measuring vertical and horizontal angles during engineering projects and surveying. However, there are certain basic differences between theodolite and total station.

What is Theodolite?

A theodolite is a scientific precision instrument which measures angles in the horizontal and vertical planes. It is mainly used for surveying operations. Some of the adapted types of theodolites are even used in fields like meteorology and rocket launch technology. To know more about theodolites, read What is a Theodolite-Types and Uses

What is Total Station?

A total station essentially is a theodolite- an electronic theodolite (transit) to be specific. Thus it can be called a type of theodolite which is integrated with an electronic distance meter (EDM) for reading slope distances between the instrument and a particular point.

Difference Between Theodolite and Total Station

The comparison of theodolite and total station can be done on a number of criteria like components, features, ease of operation, cost etc. though the basic function of both remains the same- measurement of horizontal and vertical angles.

• A theodolite has a telescope between the horizontal and vertical axes. However, the axes angle can be calculated accurately only if the operator knows enough of trigonometry. On the other hand, most of the total stations are equipped with softwares for site calibration, coordinate geometry calculations and other features for maximized productivity.
• An assistant is always required to operate for facilitating the measurement and alignment of angles. This is not the case with a total station, especially when using robotic total station as it allows the operator to work single handedly with the help of a remote control.
• A theodolite is generally suitable for surveys of small size plots whereas total stations are more suitable for survey requirements over large distances, especially for difficult terrain as their results in such environments are more accurate and dependable.
• As far as cost factor is concerned, total stations are more expensive than theodolites and also require surveying training as well as software training according to the specific product and models.

Thus, after analyzing the differences between a theodolite and a total station, it seems that total station is a superior surveying tool as compared to theodolite due to its digital integration and all-inclusive features. However, factors related to time, expertise available, and cost also determine whether one would like to use a theodolite or a total station! If you have decided in favor of total station, then there is more to decide about whether to use GPS total station or not? For guidance, read GPS Total Station- Benefits and Drawbacks

How to do Auto Level Calibration?

Those dealing with test equipments know well about calibration. It is the checking or adjusting an equipment- by comparing it with a standard- for  getting accurate measurements. Auto level is one of the many survey instruments that needs calibration. Here is a step by step instruction guide on how to calibrate auto level! If you want to do it yourself, this guide will help you in your auto level calibration.

• Open the cover of auto level by unscrewing the top, bottom, left and right screws. If you only want to do collimation (adjust accurately the line of sight), then you have to adjust only top and bottom screw.
• After opening the cover, set the auto level in the center of 2 staff (having approx length of 60m) and get the reading of Backsight (BS)-point A and foresight (FS)-point B. Ensure that the instrument is well leveled before reading. This difference of BS and FS you get by doing this is without collimation and the reading should be taken as benchmark for adjustment.
• Now shift the auto level to point D which is L/10 (L is the length of point A to point B).
• Read the nearest staff and write down the value. Add this value with the difference of BS and FS which you got in the step 2.
• Now use screw to loose and tighten bottom and up screw. Adjust slowly- if you loose top screw then tighten bottom screw and read the staff to get the “Actual value”. This way your calibration is complete and you get the perfect value or a value that has a difference of 1 mm.
• After your auto level calibration is done, get back the alignment. Go back to center of point A and B. Check the reading again. Now you should get the perfect reading.

Once you have calibrated your auto level, you will be using it in the field. For properly using as well as checking auto level, read How to Use an Auto Level? It will also give you some tips on caring and maintenance of auto levels.

Source: Melakasurveyor