An Introduction to Theodolites | Engineer Supply - EngineerSupply

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Theodolites Guide

Theodolites guide

Precise measurement of large spaces and objects is important in fields such as surveying, construction and meteorology. The theodolite is a type of precision instrument that accurately captures horizontal and vertical angles. Using these measurements, surveyors and others can accurately determine the position of objects in a given area. If you have a job that requires precise and practical measurements, understanding the types and uses of theodolites could help you find the right equipment.

infographics theodolites guide

What Theodolites Are

A theodolite is a precision optical instrument used to measure vertical and horizontal angles. It consists of a movable telescope that can rotate and pivot on the horizontal and vertical axes. Users sight multiple points through the telescope and take readings from the device to determine the angle(s) between the points.

Using these angular readings, surveyors can map out the locations of objects. In fields such as construction, the device may be used to position objects according to a plan. Additionally, the angular measurements can be used to take distance and other measurements indirectly using trigonometry.

The first such devices are described as early as the 16th century. However, the modern analog theodolite was created in 1787 by Jesse Ramsden. Today, most of these instruments are digital theodolites that use an onboard computer to measure and store angles sighted by the user. Typically, they can measure to a level of accuracy within a few milliradian or seconds of an arc.

Types of Theodolites

There are a few types of theodolites in use today. You may expect to see the following four in use on worksites:
  • Repeating: This type takes multiple measurements on a graduated scale. The results are then averaged using the mean value. This is considered optimal for circumstances in which the base it not steady or space is limited.
  • Directional: Theodolites of this type take readings through a set circle. The first reading is deducted from the second reading to determine the angle between them.
  • Electrical Digital: These digital theodolites eliminate the need for reading scales on graduated circles. Instead, they provide a digital readout of the angles.
  • Total Station: This type combines the normal functions of a theodolite with an electronic distance measurement. It also has digital data and information documentation.

How To Use a Theodolite

The exact process for using this instrument depends on the type and model. However, the general process remains the same:
  1. Mark the survey point with a nail or stake.
  2. Set up the tripod so that the instrument is at eye level. The center should be directly over the stake. Once positioned, secure the tripod legs.
  3. Level the theodolite by adjusting the legs to ensure the instrument is completely flat.
  4. Measure the distance from the theodolite to the ground.
  5. Ensure the eyepiece is focused correctly and the axes are centered.
  6. Take sightings and record measurements.

How To Read an Angle

To read the vertical axis using the device, you need to take your zero point that should be looking forward at exactly zero degrees elevation from the device. Then, angle the sight and record the angle between these two points. In many cases, you will also need to measure the angle below the zero point as well.

Additionally, you can capture the horizontal angle in essentially the same way. The only difference is that it is measure as the device rotates around its center point rather than the scope pivoting.

How To Use a Theodolite for Leveling

The instrument can also be used for leveling. Using a theodolite survey instrument and a leveling rod, point the scope in the direction of the leveling rod. You should only rotate it on the horizontal plane. The scope should be at zero degrees on the vertical plane.

By taking readings on the leveling rod, you can determine the relative height of different points. These measurements can be added to your angular readings to help completely survey an area.

Why Surveyors Use Theodolites

Completing a theodolite survey is an effective way to map out an area. It is a very accurate way to measure angles. When combined with other instruments such as electronic distance measurements or measuring chains/tapes, these angular measurements can help surveyors create a detailed plan of an area. These devices are also relatively portable and can be positioned in many different environments.

Finding the Right Theodolite For You

Blog theodolites guide

Engineer Supply has a selection of theodolites, levels and total stations. Order the right one for your needs. Plus, you can pick up tripods, carrying cases and more. We have everything you need for surveying. Explore our catalog today.

When it comes to understanding the ins and outs of theodolites, there are a handful of points that you should keep in mind. By taking the time to review the basics, you will be able to gain insight into how these tools work, their general applications, and how to get the most out of them during your next project. Look over these points and develop a more comprehensive understanding of these essential items.

Digital and Non-Digital Theodolites

One of the most important things to know about this piece of equipment is that there are typically two different kinds. One is the digital theodolite and the other is a non-digital option. The non-digital type of tool is no longer in widespread use, as it is not considered a useful or accurate way of going about procedures when a digital alternative is readily available. Still, knowing that there are two different types of tools can help you refine your search better when searching for the best fit for your needs.

The Transit Option

Another key feature of the average theodolite is the telescope mounted to it. Since this is an integral aspect of the equipment, you want to take a few points to heart when making your selection. A transit theodolite, for example, is a type of theodolite that has a shorter telescope. The shorter scope can be a large advantage for a number of jobs, so it is best to weigh out the pros and cons of each feature in order to gain more perspective on the decision.

The Benefits

There are a number of advantages that come with using theodolites. From gaining electronic readings that provide greater accuracy and less repetition, this essential tool can help you accomplish a lot. Naturally, there are several different points to review before you can pick a theodolite that fits the demands of your next project. Give yourself time to understand each feature and it can make a world of difference toward how you feel about your final decision.

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Frequently Asked Questions

Which Theodolite Is the Best?

Blog theodolites guide

The right device depends on your unique needs. Most users prefer electrical digital theodolites or total stations. These can provide even more minute readings than are possible with graduated scales. Explore our product pages to see the unique features of each model.

What Is the Principle That Makes It Work?

The theodolite can rotate around the horizontal and vertical axes independently. When it is set up perfectly level (usually achieved using a spirit, digital or bullseye level), the device’s readings are very precise and reliable. Using math, these can be further used to calculate other measurements.

What Types of Work Require a Theodolite?

These instruments are frequently used in land surveying. They may also be used in other fields such as construction, infrastructure, meteorology and rocket science. Any work that requires angular measurements in large spaces can benefit from using a theodolite.

How Accurate Are They?

These instruments are very precise. Even old-fashioned, analog versions could measure to within less than a minute of an arc of accuracy. Modern versions are within a few milliradians or seconds of an arc. Additionally, the readings are typically considered to be very reliable.

Are Digital Theodolites Better?

Modern digital instruments are very accurate and reliable. Of course, some are of higher quality than others. Nonetheless, for most users, the digital readout is easier and faster to work with. Nonetheless, some people prefer analog if that is what they are used to.

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!

#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.

#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.

#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.

#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.

#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.

#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!

#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:

  • A telescope that features erect imaging.
  • An aperture of 45mm.
  • 30x magnification.
  • 4-second resolving power.
  • Stadia ratio of 1:100.
  • Angle measurement with a minimum accuracy of five seconds at 360 degrees.
If you’re ready to pick up one of the best theodolites for surveying, be sure to pick yours up at Engineer Supply.
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