LIDAR

NAME: - AAQIB KHURSHEED AND TOWFEEQ UMAR.

COURSE: - B.E (E&C).

ENROLL NO:-2556.

SEMESTER: -7TH.

LIDAR

COMPILED BY:

CONTENTS:

• Introduction.• General Description• Brief History.• Lidar Platforms.• Basic Principle and Technique.• How Lidar works.• Lidar components• Application• Advantage.• Disadvantage.• Conclusion.

INTODUCTION:-

Lidar is an acronym for light detection and ranging. It is an optical remote sensing technology that can measure the distance to, or other properties of a target by illuminating the target with light, often using pulses from a laser.

Mobile Lidar at UNG

General description:

This is an active remote sensing technique , similar to radar but uses laser light pulses instead of radio waves.

Most lidar systems operate in near infra–red region of electromagnetic spectrum (i.e , 1064 nm).

Lidar instruments can rapidly measure the earth’s surface at a sampling rate greater than 150khz.The resulting product is a densely spaced network of highly accurate georefernced elevation points –point cloud. It can be used to generate 3-D representation of earth’s surface.

Brief History: Searchlights were used to measure the altitude of

the clouds. Measurement was done by pointing a beam of light in sky and then reading the angle at which the beam of light struck the cloud, on a device that was known distance away from the searchlight. One was then able to obtain height by triangulation.

First laser based device was constructed by G.fiocco at MIT using a ruby laser. From there,the development of lidar was sky rocketed.

Searchlight

Lidar Platforms: Airborne topographic lidar systems are most

common lidar systems. The combination of an airborne platform and a scanning lidar sensor is an effective and efficient technique for collecting elevation data across tens to thousands of square miles. Lidar was first developed as a fixed position ground based instrument for studies of atmospheric composition, structure, clouds and aerosols. Modern navigation and positioning system enable use of water-based and land-based mobile platforms to collect lidar data. Airborne lidar data are obtained by mounting a system inside an aircraft and flying over targeted areas.

Basic Principle And Technique:-

The basic idea is fairly straightforward.Laser generates an optical pulse Pulse is reflected off an object and returns to

the system receiver. High-speed counter measures the time of

flight from the start pulse to the return pulseTime measurement is converted to a distance

(the distance to the target and the position of the airplane is then used to determine the elevation and location).

How Lidar Works:

I. Directing a laser into atmosphere.

II. Use of telescope.

III. Digitalization of lidar measurement.

LASER SCANNER AND OPTICS

LIDAR SENSOR AND PHOTODETECTORS.

POSITION AND NAVIGATION SYSTEMS.

LIDAR COMPONENT

S

LASER: Airborne lidar systems

use 1064nm diode pumped YAG lasers while bathymetric system use 532nm double diode pumped YAG lasers.

Airborne YAG Laser

Lidar Scanner and Optics:

The speed at which images can be developed is affected by the speed at which it can be scanned into the system. Moreover, optic choice effects the angular resolution and range that can be detected.

Leica ALS70-HP

Lidar Sensors and Photodetectors:• The HDL-64E Lidar sensor

(shown here) is designed for obstacle detection and navigation of autonomous ground vehicles and marine vessels. Its durability, 360 field view and very high data rate makes this sensor ideal for 3D mobile data collection and mapping applications.

• Two main photodetector technologies are used in lidars:-Solid State photodetectors such as silicon avalache photodiodes and photomultipliers.

HDL-64E Lidar Sensor

Position And Navigation System:

When a Lidar sensor is mounted on a mobile platform such as airplanes or automobiles ,it is necessary to determine the absolute position and orientation of the sensor to retain useable data . For this, we have two techniques:

GPS IMU

APPLICATIONS:

1)Agriculture.

2)Wind Farm Optimization.

3)Law Enforcement.

4)Surveying.

Advantages:

1)Higher Accuracy.

2)Fast Acquisition and Processing.

3)Minimum Human Dependence.

4)Weather/light indepedence.

Disadvantages:

1)Inability to penetrate very dense canopy leads to elevation model errors.

2)Very large datasets that are difficult to interpret and process.

3)No International Protocols.

4) Precise alignment is required.

Date

Conclusion. Lidar has become an established method for collecting very dense

and elevation data across landscapes, shallow-water areas and project sites. Moreover, LIDAR can provide high degree of accuracy and more detailed information about the landscape than radar technologies .

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