What is THD on a Rangefinder – Everything You Need to be Aware of

If you are new to rangefinders you may want to know what THD is.

Let’s find out.

What Is THD on a Rangefinder?

THD stands for true horizontal distance. It allows you to measure the actual horizontal distance from one object to another based on its angle of altitude (or height).


A rangefinder measures the distance to remote objects.

Optical devices originally developed for use in surveying were later applied to other fields, including photo­graphy and the military.

They were especially useful when trying to find the range of a target such as in naval gunfire and anti-aircraft guns.



The first rangefinder telescope was invented by James Watt (1736–1819) in 1769 and was initially known as a micrometer. It was later renamed a “rangefinder” telescope.

It was made up of two parallel lines in the focal plane of a telescope eyepieces crossing an upright line. Two sliding target marks on a surveyor’s measuring rod were adjusted so they would line up with the hair in the telescope.

The length of the rod could then be calculated using trigonometry.


There has been some debate over who invented the rangefinder telemeters first. However, the Royal Society of Arts awarded William Green an award for his development of the rangefinder telemeter in 1778, even if they knew of James Watt’s priority.

He invented the first practical version of the laser rangefinder in 1778. It consisted of two parallel glass plates separated by a small gap.


Carl Pulfrich invented practical stereo rangefinders based on a patent by Hector Alexander de Groussilier.

World War II Era

During World War II, telemetry systems used optical signals between two telescopes aimed at the same object but separated by a baseline.

To determine the range to the target, measure the distance between the two telescopes and solve the skinny triangles. You can use automatic methods (using a table) or manually calculate them.

For example, if you’re trying to measure the height of someone from a long way away, then you need a really big baseline.

Telemetry devices used by ships during World War II were so large they could be seen from space. Modern telemetries use electronic technology such as laser beams or radar.


Applications include surveilling, navigating, to help focus on photography, selecting a golf club based on distance, and adjusting the aim of projectile weapons for distance.


Golf laser rangefinders are used to measure distances between points on a course, but they’re also used to determine slope and direction.

Some people think they shouldn’t be allowed in tournaments, but others say they’re fine.


A rangefinder allows a user to determine the distance between themselves and an object they’re aiming at.


Rangefinders are tools used by surveyors in forests. They use special devices called rangefinders with anti-leaf filters.

Virtual Reality

Rangefinders have been used for decades in virtual environments to detect user movement and locate objects.

How it Works

With the menu item “Rangefinder”, you can set up the built-in rangefinder’s settings as shown below:

Step 1: Press the Home key twice to enter the main screen.

Step 2: Press the UP (2) button twice to select the Rangefinder menu item. Then press the DOWN (5) button once to open

Step 3: Press the Menu button once to enter the submenus.

Step 4: Press the UP button twice to select the first option, and press the DOWN button five times to select the last option.

Reticle Type

Step 1: Choose the reticle type from the Reticle Type drop-down list.

Step 2: Press the Menu button briefly to enter the sub-menu.

Step 3: Choose one of the three reticles with the UP/DOWN buttons.

Step 4: After selecting the option from the menu, confirm your choice by pressing the Menu button (3).

You’ll see a selection reticle appear on the screen.

If you don’t use the rangefinder for longer than four (4) second intervals, the reticle will disappear from your screen.

what is thd on a rangefinder

What is THD on a Rangefinder

Simmons LRF 600 Tilt Intelligence Laser Rangefinder Review

It’s small, light, and has lots of features that both golf players and hunters will enjoy.



You can measure distances from 0 to 600 yards.

It has a precise measurement system that allows you to measure up to a yard at most, which means you can use it by pressing a single control located at the top of the unit.


This device measures both feet and inches and the units can be viewed at the bottom of the display. It is very easy for the user to select either one.

Step 1: Press the power button for five seconds.

Step 2: You’ll see two screens at once. Let go of the button when you want to select which unit you’re using.

When you turn on the device, it will automatically go back to the last used unit.

Tilt Intelligence

With the Simmons LRF 600Tilt Intelligence Rangefinder, tilt intelligence is its version of horizontal rangefinding, which gives you a true horizontal distance to your target


Underneath the viewable distance number, this angle compensated yard line shows where the ball was hit from.

These actual horizontal distances are shown for target ranges that are 99 yards or closer. For longer distances, you will only see a line of sight measurement.


This model has a variable 4x zoom lens. Those who hunt at closer ranges such as archery or those who struggle to hold their rifles steady when using a scope will benefit from this rifle.


Even though the magnification is not as good as some of the top-of-the-range lenses, it provides a clear vision for the same price range and category.


One of the best features of this camera is its built-in display screen because having numbers displayed in front of you makes things easier than mixing up two different images into one perfect shot.

Once the LCD screen lights up, you will be able to see indicators like the unit of measure­ment, how much power the batteries have left, and when you reach a target.

Unfortunately, the numbers are displayed in black, making them hard to see in low light conditions or against dark backgrounds.


It’s small and light so it can be carried around easily. Its weight (7.7 oz.) is not too heavy.


The dimensions of this product are 4.2 inches by 3.6 inches by 1.9 inches.


The waterproof case of this device makes for an attractive companion when traveling in wet weather.

Easy to Use

It’s incredibly easy to use because of the one-button operation. Just press the button once to turn the unit on and off, and then again to control the distance between the sensor and the object.


It’s currently available for around $150, which makes it a really good and affordable device that is suitable for both hunting and golfing.

It may not have all the bells and whistles that come with more expensive ones but this model does exactly what it says on the box.


Looking back through the history of rangefinder technology, we will see that it has made huge strides. Now, the THD feature is included.

Would you like to have a rangefinder with or without THD feature?

Feel free to tell us in the comments below.


  • Sarah Wilson

    Sarah is a content consultant at The Outdoor Stores where she is ready to guide you through the features of a good firearm for your outdoor activities and hunting hobbies. Her expert knowledge and intellectual skills have helped The Outdoor Stores greatly.

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