Lidar

A special light helps us see.

A tiny beam of light shoots out. It hits an object and bounces back. The light travels to the object and then returns. This tells us how far away things are.

This tool makes very good maps. It can see rocks and clouds. It can even see deep under the water.

Cars use this light to drive. A small robot on Mars uses it too. It helps them find their way safely.

It is a very smart way to look at our world.

Lidar is a way to measure distance using light.

The name comes from "light detection and ranging." It works by shooting a laser beam at an object. The light hits the surface and bounces back. A receiver catches the returning light. By measuring the time the light takes to travel, the tool finds the distance.

Lidar can make very detailed 3D models. It can scan buildings or rock formations. It can even see through clouds to study the air. Some lidar uses light that can go under the water. This is called bathymetric lidar.

Many things use this technology today. Self-driving cars use lidar to navigate. A small helicopter on Mars used it too. Even astronauts used a laser tool to map the Moon. In the future, NASA may use lidar to help robots land on the Moon safely.

Lidar is a clever way to measure distance using light.

The name stands for light detection and ranging. It is a tool that helps us see the world in 3D. Scientists use it to map the Earth and the ocean floor. It can even help robots land on the Moon safely. This technology is important because it makes very high-resolution maps.

How does this tool work? It starts by sending out a narrow laser beam. This beam can be ultraviolet, visible, or near-infrared light. The light hits an object or a surface. Then, the light bounces back toward a receiver. This bouncing is called backscattering.

The system measures the time the light spent traveling. By using the speed of light, it calculates the exact distance.

People have been thinking about this idea for a long time. In 1930, E. H. Synge imagined using searchlights to study the air. Later, the Hughes Aircraft Company made a system called Colidar. They did this in 1961 under Malcolm Stitch. It was meant to track satellites in space.

The word lidar appeared in a magazine in 1963. It is a portmanteau, which means it combines the words light and radar.

Lidar has many different uses and interesting facts. In 1971, Apollo 15 astronauts used a laser altimeter to map the Moon.

Some systems, like the Colidar Mark II from 1963, could reach 11 km. They had an accuracy of 4.5 m. Today, the USGS uses lidar for research. One example is the Experimental Advanced Airborne Research Lidar.

It can even study single molecules in the air.

You might see lidar working in your everyday life. Self-driving cars use it to help them navigate the streets. A tiny helicopter named Ingenuity used it on Mars.

Some lidar can even see through water to map the bottom. This is called bathymetric lidar. It works by using a specific wavelength of light.

This helps us understand the world around us better.

Lidar is a sophisticated remote sensing technology used to determine distances by measuring light. The name is an acronym for light detection and ranging. It functions by targeting an object or surface with a laser beam. The system then measures the time it takes for the reflected light to return to a receiver.

This process allows for the creation of highly accurate 3D models of various environments. Lidar is vital because it provides high-resolution data for many scientific and industrial fields. It can map everything from complex forest structures to the deep ocean floor.

The mechanism of lidar relies on the constant speed of light. To find the distance to a target, the system uses a specific formula. It calculates the distance by multiplying the speed of light by the time the light spent traveling to the object and back, then dividing by two.

The light used can be in the ultraviolet, visible, or near-infrared spectrum. Instead of simple reflection, lidar often relies on backscattering. This occurs when light hits a surface and scatters back toward the sensor. Different types of scattering, such as Rayleigh, Mie, Raman, and fluorescence, are used depending on the goal.

Lidar systems are categorized by how they detect energy and how they pulse. There are two main detection schemes: incoherent and coherent detection. Incoherent detection, or direct energy detection, measures changes in the amplitude of reflected light. Coherent detection is more complex and measures Doppler shifts, which are changes in the phase of the light.

Systems also use different pulse models. Micropulse systems use intermittent bursts of energy, often around one microjoule. These are frequently "eye-safe," meaning they can be used without special safety precautions. High-power systems are used for atmospheric research to measure things like cloud density, temperature, and wind.

Different applications require specific hardware and wavelengths. For example, airborne topographic mapping often uses 1,064 nm diode-pumped YAG lasers. However, bathymetric lidar, which maps underwater depths, uses 532 nm lasers. This is because the 532 nm wavelength penetrates water with much less attenuation, or loss of signal, than the 1,064 nm wavelength.

To scan an area, the laser must be directed. Some systems use a rotating mirror to scan the scene. Others use microelectromechanical mirrors, known as MEMS, which are tiny mirrors that can reorient a laser beam.

To ensure accuracy, sensors on aircraft or satellites often use a Global Positioning System (GPS) and an inertial measurement unit (IMU) to track their exact position.

The concept of using light to probe the atmosphere was first envisioned by E. H. Synge in 1930. He imagined using powerful searchlights for this purpose. The modern era of lidar began in 1961 under Malcolm Stitch at the Hughes Aircraft Company. They developed a system called "Colidar," which stood for coherent light detecting and ranging.

This system was designed for satellite tracking shortly after the invention of the laser. The first practical terrestrial tool was the Colidar Mark II in 1963. This was a large, rifle-like rangefinder used for military targeting. It had a range of 11 km and an accuracy of 4.5 m.

Lidar has reached incredible milestones in space exploration. In 1971, the Apollo 15 mission used a laser altimeter to map the surface of the Moon. This helped the general public understand the precision of the technology. More recently, the Ingenuity helicopter used lidar for navigation during its flights on Mars.

NASA also views lidar as a key technology for future missions. It will help enable the safe, autonomous landing of both robotic and crewed vehicles on the Moon.

Today, lidar is integrated into many modern technologies. Autonomous cars use lidar sensors to navigate complex streets and avoid obstacles. In agriculture, lidar can be used to analyze the yield rates of different fields. It is also essential for atmospheric physics and meteorology. Scientists use it to study clouds, aerosols, and even single molecules in the air. From mapping ancient archaeological sites to tracking passengers in airports, lidar continues to expand its reach.