What is Trilateration Survey? Advantages and Disadvantages of Trilateration Survey

What is Trilateration Survey? Advantages and Disadvantages of Trilateration Survey

What is Trilateration Surveying?

Trilateration is a surveying procedure in which the lengths of the sides of a triangle are measured, generally electronically, and angles are determined based on this information.

It is a technique for controlling extension, breakdown, and densification that uses electronic distance measuring instruments (EDMIs) to determine the lengths of triangle sides rather than horizontal angles, as in triangulation.

The field techniques for trilateration are similar to those for triangulation, with the exception that only lines are measured while all angles are calculated.

It’s a process used for determining the position of objects on the surface of Earth, involving measuring the distance and angles between three points called trilateration stations, where all three points can be either on land or at sea.

To do this, triangulation distances are measured between each station and then converted into coordinates that represent a point on Earth’s surface, which allows accuracy to be calculated based on already known distances and angles.

History of Trilateration Surveying

Trilateration surveying was used in the Greek and Roman empires as well as later during the Renaissance. However, it was not until the end of World War 2 that it became widely used.

Trilateration, a method of surveying in which the lengths of the sides of a triangle are measured, generally electronically, and angles are determined based on this information.

A surveyor can acquire various lengths and angles that would not be quantifiable otherwise by erecting a sequence of triangles near to one another.

Due to the difficulty of the computations needed, trilateration was formerly infrequently utilized in comparison to triangulation, a method for finding two sides and an angle of a triangle given the length of one side and two angles.

However, the advancement of electronic distance-measuring instruments has made trilateration a widespread and favored approach.

The field techniques for trilateration are similar to those for triangulation, with the exception that only lines are measured and all angles are calculated.

Instruments used in Trilateration Surveying

The commonly used instruments are;

Distance Measuring Unit (DMU)

These are instruments used for measuring the distance to a target object.

Angle Measuring Device (ADM)

These are perspective instruments used for measuring the angle to a target object or between two known objects.

Total Station

An instrument that can be used to make measurements of length, angles, and heights as well as provide digital data sets.

The distances and angles are taken by total stations which are then processed on computers with software such as Leica’s Topcon’s LTS2000 stations or Trimble’s Total station software.

Trilateration Station

This is the equipment used in trilateration surveying.

Trilateration stations are usually composed of a distance measuring unit, an angle measuring instrument, a total station, and reflector panels.

Reflector panels are placed at each station so that even when there is no direct line of sight between two stations, the one can be still seen by the other.

The reflectors can be made of any suitable material to reflect light back to the target station, such as mirrors or prisms.


A theodolite is an instrument used to measure the angles and vertical angles between objects. This is done by measuring the angle a target object makes with respect to an object that has already been measured.

The target object is called the “horizon axis”. A telescope on a horizontal plane is mounted on one of the stations, and its line of sight intersects another station where a target mark is located

Trilateration Triangle

A survey triangle that represents the position of one or more points on Earth’s surface typically made up of connecting lines between digital total stations.

Angle measuring instrument (AMA)

A device used to take angles.

Distance measuring device (DMA)

A device used for measuring distances.

Meridian circle

An instrument is used to find the azimuth of a target object by taking measurements.

Trilateration Surveying Applications

The areas where Trilateration Surveying is applied include:

  1. Trilateration surveying is used to measure the heights of offshore facilities, such as platforms and pipelines.
  2. Trilateration surveying is also used to measure the height of numerous structures such as bridges, church steeples, radio towers, and skyscrapers.
  3. Trilateration surveying is used in urban planning for the placement of roads and buildings.
  4. Trilateration surveying is also used for agricultural planning for optimal planting and harvesting methods of land outside cities.
  5. Trilateration surveying is used for identifying and locating, fuel storage tanks.
  6. Trilateration surveying is used for the identification of previously unknown water sources, such as underground aquifers.

Trilateration Surveying Advantages

They are as follows:

  1. Trilateration is a cost-effective method because the equipment required for its operation is rather simple.
  2. Trilateration is also easy to conduct if the surveyor has knowledge of mathematics and geometry.
  3. Trilateration is more accurate than other surveying methods such as triangulation, which either requires more equipment or extra time during the survey process.
  4. Trilateration is very time effective and can be conducted either during the day or night.
  5. This method of surveying is easy to repeat and can be repeated if necessary.
  6. Trilateration surveying requires low training and is not subject to human error, which may occur in other surveying methods.
  7. Trilateration surveying requires accurate measurements of time, which can be easily acquired with the use of a chronograph.
  8. The surveyor need not be concerned about the measurement of angles and distances because these measurements are performed by electronic instruments that take these measurements automatically and without error.

Trilateration Surveying Disadvantages

The disadvantages are;

  1. Trilateration surveying cannot measure areas that are irregular or shapely, such as round corners or complex topography.
  2. The surveyor may not be able to see two or more stations at the same time, which would render trilateration useless in that particular area.
  3. The surveyor has to spend time making equipment adjustments and putting reflectors in the right place without interruption.
  4. Trilateration surveying requires a large amount of patience and attention to detail because of the many calculations that must be made during the process.

Trilateration Surveying Issues

Trilateration Surveying issues are discussed below.

  1. Trilateration surveyors must make sure that the point being measured is not referring to a non-existent reference point.
  2. A trilateration survey often requires multiple lines to be surveyed with several measurement repetitions, which could be costly and time-consuming.
  3. Trilateration requires precise measurements at each station, which makes the survey more difficult than other surveying techniques.
  4. Without proper planning and well-executed techniques, this method is not accurate enough for today’s standards.
  5. Sometimes surveying in low visibility conditions, such as dark rain or fog can be difficult because the reflection and illumination of the instruments are affected.
  6. It is also important for a surveyor to know that there is no set procedure for how to use trilateration, thus requiring extensive training and practice to become proficient with this technique.

Trilateration Survey Procedure

There is a great deal of variation in how trilateration surveying is done between countries and companies. Although, most companies and countries follow a similar process when carrying out trilateration surveys.

  1. First, a field survey must be chosen with the right number of points to make sure that the surveyor can work with the available manpower and budget.
  2. The surveyor uses distance measuring equipment (DMU) to measure the distance between two or more stations, which may be reflectors or known points on the surface of Earth.
  3. The surveyor must then calculate the average distance that the targets are apart and enter it into an electronic calculator or computer for further processing.
  4. The surveyor may need to check their work using a total station if the targets are not in a direct line of sight with each other.
  5. Once distances have been measured between all points, the surveyor may need to calculate angles at certain stations, such as a meridian circle, in order to determine location.
  6. If the surveyor cannot determine location using the measurements and calculations made, he or she may need to visit certain stations and adjust reflectors or targets.
  7. Once a location has been determined it is important to verify it by comparing the results with traditional surveying methods, such as triangulation.
  8. Trilateration surveys can be repeated, if necessary, but the surveyor should take into account possible changes in the target’s position and orientation between each measurement to ensure accuracy.

Trilateration Survey Accuracy

At first glance trilateration may seem to be a simple and quick method of survey, but it turns out that the reality is not quite so cut and dry.

In many cases the accuracy of trilateration far exceeds that of other surveying methods, such as triangulation, but there are some problems which have been noted.

Trilateration seems to be much more accurate than traditional triangulation when it comes to locating buildings and other geodetic features on a vertical axis.

The exact location of a building or other man-made structure can be located within one-tenth of a foot with the use of trilateration.

When it comes to horizontal distance measurement, trilateration is not quite as accurate.

The accuracy of horizontal measurements is often less by about two feet than those taken by other surveying techniques, such as triangulation.

Trilateration surveys also appear to be slightly off when compared to data obtained from Global Positioning Systems (GPS) or satellite images. As a result, many surveyors and companies tend to either ignore trilateration results or double check them using other methods.

Trilateration Survey Methods

Trilateration can be performed in three different ways. The surveyor can either use one reflector, two reflectors or multiple reflectors.

Trilateration surveying can also be performed using two different methods,

The two methods are:

  • The direct-line method- can be done by using only one reflector or by using a series of reflectors to form a line.
  • The traverse method -can be performed by using a series of surveyors to make measurements from different angles.

Although a simple surveyor can perform trilateration surveys with minimal training, it is recommended that professionals who work with electronic equipment use these methods to make the most accurate surveys.

Trilateration Survey Software

Trilateration requires much mathematical calculation, so there are a few different programs available which will help the surveyor or engineer complete these calculations.

Trilateration software can help surveyors perform trilateration surveys more accurately by streamlining and automating the calculations that would have to be manually performed otherwise.

There are also programs available that will work with GPS units, total stations, and other electronic equipment to give the survey worker or engineer accurate results.

These programs can be very valuable during trilateration surveys because of their ability to streamline process and give rapid results.

Trilateration Surveying in the World

Trilateration is often used along with GPS surveying to make sure that surveys are as accurate as possible.

Trilateration is becoming more common in the U.S., where it has been used for some time now on highways and other transportation projects.

It is estimated that over 60% of highway building projects are carried out using some sort of trilateration technique.


What is the difference between triangulation and trilateration in surveying?

Trilateration measures distance to determine GPS satellites’ exact position on Earth as they transmit their location and time. While surveyors use triangulation to determine distances between sites, GPS positioning does not employ any angles at all.

What is the difference between a trilateration survey and a traverse survey?

The most accurate method of trilateration surveying is the direct-line method, which uses only one reflector. In a traverse survey, multiple surveyors will measure distances from different angles.

Is it more expensive to use trilateration surveys than other surveying methods?

Surveyors do not need to purchase all the necessary equipment, such as measuring tapes and benches, to perform a triangulation survey. While it is not uncommon for surveyors to use triangulation surveys on transportation projects, trilateration surveys can be just as cost-effective.

What is a simple trilateration survey?

A simple trilateration survey requires less than one mile of straight-line distance between the targets. A traverse survey uses multiple points to determine distance in order to get more precise measurements.

Why is trilateration more accurate than triangulation?

Trilateration surveys are more accurate than triangulation because the straight-line distance between reflectors is generally easier to measure than angles.

How long does it take for trilateration to work?

As long as there are no breaks in GPS signals, a surveyor should be able to accurately determine a location within one minute after starting the survey. Usually, however, it takes longer to get an exact location due to data transmission delays.

Why is GPS positioning not affected by electromagnetic interference?

GPS satellites communicate with each other and control the timing of their transmissions to eliminate errors. In addition, the GPS signals are sent on a high frequency that is not susceptible to interference from manmade devices.

Which is more accurate triangulation or trilateration?

Trilateration surveying is more accurate than triangulation when it comes to determining distances between a building and a directly overhead reference point. However, trilateration surveys can be off by as much as two feet, while most users of triangulation have found accuracy to be within one foot.

Is trilateration more time-consuming than other surveying techniques?

Trilateration involves fewer steps than some other methods of surveying and is often faster in rural areas or less populated areas.

What is a trilateration algorithm?

A trilateration algorithm is a mathematical computation used to determine the distance between a target reflector and a GPS satellite.

What is trilateration surveying?

Trilateration surveying includes any process by which surveyors use electronic devices such as reflectors or GPS technology to determine the location of a point on Earth’s surface.

How do you calculate trilateration?

Distance = Rate × Time

Time = Rate ÷ Distance

Distance = Rate × Time

Time = Rate ÷ Distance

How does trilateration help save time?

Using trilateration surveys can save time because it allows surveyors to accurately determine the distances between different locations.

How does GPS work trilateration?

Trilateration works by determining your position on Earth after the location of GPS satellites circling the Earth and their distance from you are known.

However, with a third satellite signal, we can pinpoint our device’s exact position since the three spheres will only connect at one spot.

What is the role of the second satellite used in trilateration?

Trilateration is a high-tech variation of triangulation. The first satellite pinpoints your location on a sphere. The second satellite pinpoints your position as a circle formed by the intersection of the two satellite spheres.

What is the difference between 2D and 3D trilateration?

3D trilateration is similar to 2D trilateration, except instead of circles, intersecting spheres are used. What are the two things that GPS receivers must perform in order to find a location?

Where is trilateration used?

Trilateration is a cost-effective positioning technique for control surveys because to advances in electronic distance measuring technology.

Trilateration is utilized not just by land surveyors, but also by GPS satellites and receivers to determine location coordinates.

What are the various geometrical figures used in trilateration?

Braced quadrilaterals and center-point polygons are the most common geometric forms used in trilateration. However, due to a lack of internal controls, defined requirements and standards must be strictly followed.

What is trilateration How is user position computed?

Trilateration is the process of finding your position by knowing your distance from at least three known places. The satellites themselves are the known positions in GPS.

It is critical to recognize that this is a simple exercise in trilateration and not a precise illustration of how the GPS positioning mechanism works.

What is an example of trilateration?

The first satellite, for example, emits a signal that finally reaches your GPS receiver. Because we have a third satellite, the intersection of all three circles indicates your real position.

Trilateration may locate an exact position by utilizing three distances.

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