How to Use Theodolites

Steps for Proper Theodolite Use

Theodolites are precision instruments designed to measure horizontal and vertical angles in surveying applications. These instruments come in digital and analog options and use many complex parts to achieve accurate readings. Follow these steps to set up your theodolite and prepare for accurate readings.

Mark the Point

Start with the point where you will set the theodolite. The point needs to be accurately marked, as this will form the basis for measuring distances and angles.

Consider using a surveyor’s nail or stake to mark the point. This will ensure you keep an accurate, stable point as you move on to other steps in the process.

Set up the Tripod

The tripod needs to be stable and adjusted to the correct height. Once correctly adjusted, the theodolite should be at eye level. This needs to be adjusted carefully to keep it stable and keep the mounting plate centered on the stake or nail.

In some cases, the point you choose to place the theodolite may need to be adjusted to make room for the tripod. Be sure you have a spot cleared where you can place a tripod without worrying about it tilting or being placed on unlevel ground.

Mount the Theodolite

Once the tripod is firmly set, it’s time to place the theodolite on it. Dropping your theodolite can cause permanent damage, so always make sure the tripod is firmly in position before you attempt to mount the instrument.

Most theodolites come with screws and mounting knobs. Verify that your particular instrument and tripod can easily connect, or you may not have a stable surface as you start to use it. Follow the instructions carefully for a firm attachment, since tripods and instruments have differing mounting brackets and knobs.

Measure the Height

Before you can start taking accurate measurements, you need to take a reference distance. Measure from the ground to the theodolite. This distance will serve as a reference to other stations as you use the instrument.

Level the Theodolite

Your instrument should have a built-in spirit level. Using the bulls-eye level, check to see if your tripod legs are properly adjusted. Make adjustments as necessary using the legs and the leveling knobs until it’s properly positioned.

If you aren’t able to firmly place and measure the instrument, then you may need to select a new position. When this occurs, you may need to repeat the initial steps to ensure the correct height and theodolite setup.

Adjust the Small Sight

The vertical plummet, also known as the small sight, is on the bottom of the instrument. It’s important that this sight is adjusted to remain over the surveyor’s nail or stake. There should be knobs on the bottom of the instrument to allow you to make fine-tuning adjustments until the small sight is in the correct position.

Aim the Crosshairs

Finally, it’s time to aim the crosshairs of the main scope. Point at the spot you wish to measure and lock the instrument in place using the locking knobs. Take the vertical and horizontal angle measurements using the viewing scope. This should be on the side of the instrument.

These steps complete the theodolite survey. Choose a theodolite for more accurate angle measurements than a transit level. These survey steps are commonly used for building corners or identifying lot lines, but they can also be used to form panels, align wood frames or for navigation purposes.

Frequently Asked Questions

How Do You Read a Theodolite?

A theodolite uses a Vernier Scale to accurately measure angles. You must use the inner and outer scales to identify the correct degree marking, and angle, you’re viewing. Use of this scale can take some practice, but is the accepted standard for accurate, comparable measurements using this style of instrument.

How Is a Theodolite Used To Measure Distance?

Many surveying instruments, like the theodolite, use tachymetry, which uses the vertical distance on a vertical staff to measure the distance between the instrument and the staff. The result is an accurate measurement that can be used in navigation, construction and other situations that require precision angle and distance measurements.

Do Surveyors Still Use Theodolites?

Yes, these instruments are still being used by professional surveyors. They are also used for meteorological and navigation purposes. Both analog and digital instruments offer accurate, repeatable measurements that are still used in professional settings. As long as the instrument is properly cared for, it can provide accurate readings that don’t require repeat measurements to verify accuracy.

How Is Analog Theodolite Used?

This style of instrument has been largely replaced by the digital theodolite. You can still use an analog instrument, but you must read graduated circles and identify an accurate reading, rather than rely on precision digital readouts to verify the exact angle and distance. In most cases, digital instruments are preferred for professional use.

Where Can You Find a Theodolite

Be sure to shop for a theodolite at a reputable engineering and surveying supplier. These precision instruments can be used for a variety of purposes, but a name-brand option provides you with a long-lasting investment and accurate readings. A quality supplier can also help you learn more about caring for your theodolite and help you find replacement parts.

Shop for a theodolite today at Engineer Supply to find an accurate instrument for your next project. Explore the various styles, brand names and features with the help of our highly organized online catalog to identify the best instrument for your next project.

Best Theodolites

#1: Topcon Theodolite DT-307L with Laser Pointer

This theodolite integrates the same advanced circle reading technology found in Topcon’s high-performance total stations, so you can do more accurate calculations while you’re out on the field. Topcon continues to include high-quality optics and electronics in all their theodolites, and this particular model can endure any kind of wet or dust condition that you may find while you’re out in the field. This will keep you productive regardless of the surrounding weather. This theodolite also comes with the following accessories:

Plumb bob.
Tool kit.
Lint-free lens cloth.
Waterproof protective cover.
Hard carrying case.

Be sure to pick yours up at Engineer Supply today!

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#2: Leica Digital Electronic Theodolite

This digital theodolite is an economical but sophisticated tool for measuring angles and slopes with a five-second accuracy. It also has a laser plummet for quick and easy setup, a reticle illuminator for a brighter view, as well as many other attractive features.

It’s a great tool for even the most demanding job requirements, and the automatic vertical angle compensator (which can be turned on or off) will make sure you get an accurate reading if the instrument moves out of balance. If the theodolite moves out of the compensation range, it will display a tilt warning in the vertical angle reading space (which can help you to avoid any costly errors).

Both sides of the instrument have back-lit LCD display panels, which will allow you to access functions from either side. And both of them are easy to read, even in low-light conditions. This digital theodolite has a number of other features, which can include:

Horizontal angle indicator that can help with faster orientation.
Numerous customization options.
IP54 Rating for water and dust resistance.
NiMH rechargeable battery pack with a charger.
AA alkaline battery holder for an additional power option.

If you’re ready to purchase this theodolite, be sure to pick yours up at Engineer Supply.

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#3: Futtura 5-Second Digital Theodolite

This theodolite can give you more accuracy at a lower cost than most of the standard models. It comes with a NiCad battery and charger, as well as an alkaline battery pack. It also has two LCD displays that can be used with a large push-button system. It has flexible mounting options with its removable tribrach, and it will fit any standard 5/8” x 11” flat or dome-head tripod.

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#4: GeoMax ZIPP02 2-Second Digital Theodolite

With a vertical compensator and a 2-second accuracy, this theodolite will give you the precision you need for even the most demanding jobs. It has a variety of display modes and measurement units. It’s also easy to operate with only six keys, and it comes with a laser plummet so you can make sure it’s set up correctly. When you purchase this digital theodolite, it will come with the following accessories:

Hard carrying case.
Tribrach.
Rechargeable battery.
Charger
Alkaline battery cassette.

It also has an IP54 Rating for dust and water resistance as well as a 36-hour battery life.

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#5: David White DT8-05LS 5-Second Laser Sight Digital Theodolite with Optical Plummet

This theodolite has a laser beam built into the aperture, so it can be easily and accurately aligned. And the simple, push-button functions will give you precise digital readouts on an LCD display. It also has an incremental encoding system with two digital displays and an automatic power shut-off system. The coaxial tangent and clamp screws will make sighting and alignment easier, and it even has an optical plummet for better point centering.

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#6: Futtura 10-Second Digital Theodolite

This theodolite uses rechargeable NiCad batteries (charger is included) as well as an alkaline battery pack. The two LCD displays have large displays, which makes it easier to read. This design allows you to get an accurate reading from either side of the machine. The built-in crosshair, display illumination, and simple push-button operation makes it easy to use. And the removable optical plummet (with its ability to fit flat or dome-head tripods) will give you more flexibility.

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#7: SitePro 5 Second Digital Theodolite

The incremental encoding detection system and dual digital displays on this theodolite will allow you to get precise readouts that are easy to read, and the 30x telescope will give you a bright wide field. The built-in 3x optical plummet will allow you to set it up quickly and easily. It also has a 5-second vertical and horizontal accuracy, so you can get precise readings in even the most demanding situation. This digital theodolite comes with a variety of other features, including the following:

Automatic power shut-off.
Optical plummet for centering of point.
Coaxial tangent and clamp screws to make sighting and alignment functions easier.

Be sure to pick yours up at Engineer Supply today!

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#8: Northwest Instrument 5-Second Digital Theodolite

This theodolite has photoelectric incremental encoding that will make sure you get precise results. The horizontal and vertical measurements are displayed on dual-sided LCD displays. And it has a number of other features, which includes the following: