How Do Rangefinders Work – Know The Basic Science Behind It!

How Do Rangefinders Work

Rangefinders are devices used to measure the distance between the target and the observer using a ‘ranging’ process. Ranging is used to describe distance measurement in relation to moving objects.

Most ranging methods would take time travel measurements into consideration, that is, the time difference between different signals that are received is used to calculate the exact distance.

However, ranging can also be done without an accurate synchronization of the receiving signal. This type of ranging is called pseudo-range, a common example is the GPS, Global Positioning System.      

How Do Rangefinders Work

Rangefinders are applied in a varied number of things, like surveying, navigation, photography focusing, golfing, and even hunting. Rangefinders work in different unique ways that we are going to learn about during the course of this article.

Active range finding methods include lidar, laser, sonar, RADAR, and ultrasonic range finding using methods like passive reflection and unilateral transmission.

Essentially, a rangefinder is a device that offers the quickest and easiest way to assess or calculate the distance to a target object in order to aid accuracy in target hitting.  Before the development of rangefinders, people used their eyes to try to gauge the location and distances of objects but with the rangefinder device, technology can be infused into target hitting and accuracy.   

We will be learning how the different types of rangefinders work but before then, we would take a look at the different types individually, to know why they are different and unique. Lets see how do rangefinders work.

Types of Rangefinders

There are several types of rangefinders in the market today and their performances are usually measured by accuracy, range, weight, size, or ease of use in certain field conditions.

The different kinds of rangefinders fall within the 3 major types;

  1. Laser Rangefinder
  2. Optical Rangefinder
  3. Ultrasonic Rangefinder

Under these 3 common rangefinder technologies, you will find the different kinds of rangefinders like; golf and hunting rangefinders. Now, let’s take at them in detail.

Laser Rangefinder:

Laser rangefinders use laser beams to calculate the distance of an object, this rangefinder type uses light beams to capture and process the information of distant objects. It does this by using active optical processes like light reflection.

Simply put, distance is determined by the amount of time needed for infrared light to get to the target and back. The equation or calculation for the speed of light is always constant, the only variable is the distance of the object. Now coming to the point how do laser rangefinders work.   

How do Laser Rangefinders work?

How Do Laser Rangefinders Work

The laser rangefinder works as an electron-optical device optimally designed to measure the distance of a target or the distance to a target using the fastest means possible. It has a multiplicity feature coupled with high-quality optics that comes with an aiming and clearing grid that is armed with a digital processor.  

As I mentioned before, the laser rangefinder makes use of light beams to capture and process information about distant objects. It uses light reflection and the way light scatters through a transparent and semi-transparent medium.

The laser beam released from a rangefinder is typically quite narrow but atmospheric factors like air, mixes with the light beam and it diverges and is spread out through long distances. When this diverged light gets to the target object the once narrow beam light is now wide enough to cover the object and reflect back to be measured.

The computer calculates the passage time of the light beam or ray to get to the target object and adds it to the passage time for the beam to return to the rangefinder. Then it multiplies it by the speed of light and divides it by two times the value of the refractive index of whatever medium is being used.

The value gotten is the distance of the target object from the observer or point of observation. However, we must keep in mind that a number of things could affect or improve the accuracy of the distance measured. We would look more into these factors as we progress with the article.

There are certain target objects that their distances cannot be determined. A common example is a glass pane. This is because the light will completely pass through the glass and wouldn’t be reflected back for calculation at all.

Other objects that could be impervious to this rangefinder include mirrors or any other object that is angled or tilted in a certain degree that enables the mirror or the object to deflect some of the light away.

The remaining light is reflected back to the rangefinder, the amount of light reflected back determines how easy measuring the range would be for the range finder. This rangefinder is one of the most common types in the market.  

Optical Rangefinder:

Optical rangefinder devices measure distant target objects by using several lenses and mirrors to create a double image. The double image created on the mirrors is merged into one image by continuously rotating a dial. The rotating dial itself is a distance indicator and after the images are merged together, the distance of the target object can be seen on the dial.      

In simple terms, an optical rangefinder is a device that makes use of visual and automated standard systems to aid the distinct separation of a target object by an observer. Now coming to the point how do optical rangefinders work.

How do Optical Rangefinders work?

An optical rangefinder is primarily made up of two focal points and a long cylinder. Two crystal features that can adjust the output without altering the light are built into the light-way of the two focal points.   

Optical rangefinders use the two types of ranging principle;

  1. Stereoscopic Ranging Principle
  2. Coincidence Ranging Principle

The stereoscopic range finding principle makes use of the two operator eyes and then aligns the reference markings inside the reticle in order to measure the distance. On the flip side, the target images of the coincidence rangefinder are reflected from two separate sources and they are shown to an operator that uses just one eye to look into the instrument.

In this principle, an adjustment must be made inside the reticle in order to match the alignment. The images aligning is typically called putting them into coincidence and that is how this principle gets its name. The number of adjustments needed for the images to get into coincidence is how the ranging device measures the distance to the target object.     

Ultrasonic Rangefinder:

The ultrasonic rangefinder device uses soundwaves to measure the distance of target objects. It uses a wide band frequency produced from a transducer. This process produces narrow soundwave beams that target a distant object and then bounce off it.

The returning soundwave signal is received by a handheld receiver that measures the distance of the target object. The accuracy of this rangefinder type can however be affected by external sound waves, extraneous noise, and the position of the receiver. Now coming to the point how do ultrasonic rangefinders work.    

How do Ultrasonic Rangefinders work?

This rangefinder type is a high-frequency sound wave type that cannot be heard by human ears because it is higher than the frequency humans can hear, which is about 20,000 Hz. The soundwave is targeted at an object and when they hit the target, they bounce back and the distance of the target object can be calculated using the speed of the sent sound wave and the speed of sound which is 330 m/s.    

This range finding type is mostly restricted to applications in parking or car sensors but it isn’t really efficient for a long-range target object.  

Other types of Rangefinders

Other types of Rangefinders include;


The full meaning of RADAR is Radio Detection and Ranging. This ranging type is almost similar to the laser rangefinder type, the only difference is that while the laser rangefinder sends out laser light beams, the RADAR uses a radio signal. However, the calculation remains the same for both of them because radio waves travel at the same speed as the speed of light.

RADAR rangefinder signals can cover a wide and long-range because of their long wavelength. It is commonly used to determine the distances of target objects like ships and aircraft in an open space. This ranging type is not impacted by weather conditions like fog and cloudiness, it can be used in varied weather conditions including sunny days and at night.

2. Lidar:  

This ranging type works with the same principle as the RADAR and Laser rangefinder but on a much bigger scale and capacity even though its range is much shorter compared to the RADAR. This ranging type sends out light pulses across a wide space instead of using radio waves or sound waves. This ranging type can be affected by certain weather conditions unlike the RADAR rangefinder like clouds and fog. However, it is pricier than the RADAR type because of its small object detection feature.

3. Sonar:  

This ranging type works quite similarly to the Ultrasonic rangefinder because they both use sound waves to measure distances. The speed of sound is used to calculate the time the sound waves travel to and fro the target object. The Sonar rangefinder is also used underwater, where light and radio waves cannot travel easily

While these rangefinder types cannot be used in common range finding applications like shooting, hunting, and golfing amongst others, they are worth mentioning because they also serve their own unique functions.

Uses and Functions of Rangefinders

Functions of rangefinders differ by range finding type and functionality and we will look at the different common functions by the types of rangefinders that can be used for those specific functions.

1. Golfing:

Golf rangefinders are used by golfers to improve tin their sport. Two types of rangefinders are most commonly used for golfing and they are the laser rangefinder and the GPS also known as the pseudo-ranger.   

The GPS rangefinder requires much less time to determine the distance to the target hole for the golfer or any other target point in the golf course field. A certain advantage that the GPS rangefinder has is its ability to determine accurate distance even in regions of greenery. It utilizes GPS technology hence users are not required to hold and focus the device in a stable stance or pace.

It gives the output of the golf course layout quite easily and it is also easily activated and used to determine required readings. In determining precise accuracy, however, the laser rangefinder is far ahead of the GPS. GPS rangefinders can come as branded watches or handheld GPS and they have to be charged from time to time because they are powered by batteries.     

The Laser rangefinders are not as easy and straightforward compared to the GPS and they take more time to produce measured distance results. It has a very precise technology that produces accurate distance measurement results. It has a long battery life and an optimally efficient design that does not require frequent charging like the GPS. When it comes to precise targeting, they are preferable to GPS.

However, they do have certain shortfalls like, not being able to process targets surrounded by environmental factors like trees, hills, and slopes but this has been counteracted by the emergence of hybrid types of laser rangefinders. These have features that allow them to detect flags, self-stabilize, and makeup for the hilly and sloppy environs.

2. Hunting:   

Hunting comes in different forms and the rangefinder used is determinant of this fact because hunting style differs from one type to the next. The different style of hunting is best suited to be done using a rangefinder that is meant for that style of hunting.

3. Archery and Bowhunting:

This type of hunting usually requires a rangefinder type that is sleek with angle compensation features and designs. They are typically built to be held in an upright fashion, this makes them lighter than other rangefinder models that are level model types. Their sleek and compact design enables them to be easily and comfortably holstered or tethered when needed. The rangefinder used for this kind of hunting does not necessarily have to be wide or long-ranged like a rifle shooting kind of hunting.   

4. Rifle Hunting and Rifle Shooting:

This kind of hunting requires a rangefinder that can cover a longer range of distance targeting a typically smaller object. The higher the range power of the rangefinder model, the more precise or accurate distance reading it would produce. This long-range distance coverage may have to be compensated for by walking through certain distances, this is why getting a compact and light model type of rangefinder for this purpose would be wise.

Magnification capability for this function is also very important for precision. Purchasing a rangefinder model with about 7-8x magnification is required for this use. Some hunters use the rangefinder along with the rifle scope which is used for aiming and shooting at the target object. The magnification is even more important because this rangefinder is usually used for long ranges targeting smaller objects.         

There are also double functional hunting rangefinders that can be used for both archeries and rifle hunts.

5. Surveying:

A typical forest surveying rangefinder works by determining the distance of the trees that are nearby, calculating the distance of a specific spot from another spot and the height of the trees around the region, and finding a plot center. The rangefinder can also be used to measure the standing of trees like timber and also determine the volume of any target tree.

When purchasing a rangefinder for surveying, you must keep in mind that you are in rugged or uneven terrain and you would be required to walk for an extended period of time, even navigate regions that are higher than you accounted for. Some very important things to consider would be the weight, size, and functionality of the rangefinder you are to use for surveying functions.

6. Photography:

Photography took a new turn with the introduction of rangefinder cameras. It can be used by both amateurs and professionals who are looking to improve their craft in the field of photography. The rangefinder camera offers a lot of amazing features that include high-quality output, flexibility, and mechanization. It also features a modifiable focusing design that affords photographers to take clear and precise shots of their target objects.

It has a viewfinder that allows the display of up to two images, the modifiable focusing feature of the camera aids the viewfinder when it brings both images displayed into one precise and focused image. This modifiable focus feature can be adjusted with a turning wheel. The camera helps the photographer determine the distance of the person or object being captured in order to get a well-defined and focused shot.   

With the creation of the range-finding cameras, merging of images and focusing happens in a considerably less amount of time, real-time even, sparing a lot of photographers a lot of stress and resources. However, the range finding camera is not popular in the world of photography anymore because of cameras that offer the same functionalities and even more, like the DSLR cameras that can be set on Automatic mode and they have more adjustable features and they do not particularly require photographers to have special knowledge. As for the range finding cameras, there are digital models as well as the standard single-lens reflex models.   

The Best Rangefinders:

Now that we have an idea of what rangefinders are and how they work, let us take a look at some of the best rangefinders in the market. We would be going over some examples of rangefinders and what makes them the best.

Impulse 200:

Some of its best features include

  • It has an automatic shutoff
  • It measures height, vertical, horizontal, and sloppy distances. As well as inclination, cumulative, and difference in distances
  • It can measure very small units of 0.01 feet
  • It is a laser range finding device with an operating range of about 1,650 feet
  • It offers 20 hours supply of service with continuous usage with just two AA battery supply

Sonin 60:

Some of its best features include

  • It can measure very small units of 1 inch
  • It can calculate volumes, areas and also add and subtract
  • It has a measurement convertible feature, like converting meters to centimeters or feet to inches
  • It has an automatic shutoff feature
  • It is an ultrasonic range finding device that operates within a range of 1-60 feet

Lytespeed 400:

Some of its best features include

  • It gets its name from its operating range capacity. It can operate within a range of 400 yards without a reflective target and 999 yards with a reflective target
  • It has a yard to meters converting feature
  • It has an automatic shutoff and a low battery indicator feature
  • It has a shock and water-resistant feature
  • It is a laser rangefinder that operates as an infrared device

Ranging 400:

Some of its best features include

  • This model has an image and calibration adjustment feature
  • It doesn’t require a battery
  • It can measure very small units of 0.5-1 yard
  • It has a 3x monocular to improve focus and precision
  • It is an optical range finding device that can operate within a range of 20-400 yards

Laser Ranger Finders:

We have learned a lot about laser range finders and now we are going to be looking at some of the best types of laser rangefinders to buy when you are looking to get one. Laser rangefinders fall into the different categories of range finding functions, like hunting, golfing, and foresting, and surveying. It is no surprise that they are very popular and saturated in the market today.

  1. Leupold RX-950 Laser Rangefinder
  2. Nikon ProStaff 1000i Laser Rangefinders
  3. Yardage Pro Rangefinder
  4. Leica Geovid HD Binoculars
  5. Vortex Optics Impact Laser Rangefinder
  6. Bushnell Trophy Xtreme Laser Rangefinder  

Some of these model examples are ridiculously inexpensive and offer great quality and service at the same time while some like the Nikon lineups lean towards the premium and expensive side.

Key Features to look out for in Rangefinders:

Whatever brand or model range finding equipment you decide to go with, there are specific things that would determine if your rangefinder device would either suck or be amazing at what you intend to use it for, and some of those things to look out for include;


I believe this is a no-brainer because the whole purpose of a rangefinder, to begin with, is to accurately calculate and determine the distance to or from an object. A rangefinder with crappy accuracy might as well never have been created in the first place. Always look out for rangefinders with great accuracy readings and 90 percent of your job is done.


I mentioned this earlier in the article, some rangefinders offer up to 8x magnification ability. People often need rangefinders to view distant target objects and distant target objects would naturally appear smaller to the observer. Having a rangefinder that can increase the object is a winner.

Battery life:

Nobody wantstheir devices to die on them in the middle of a project or a sport and usually, a rangefinder could be great in every other region and have questionable battery life. This is why getting a rangefinder with a good voltage capacity is a requirement in my opinion.

Other things to look out for that are also very important include; Angle detection, Durability, and compactness of design.   


In conclusion, rangefinders are a necessity if you intend to get better at hunting, golfing, surveying, and photography as well. They improve accuracy and precision and can act as your automated, robotic, and capable third eye.