1. 1. Compiled by- Atul Anand(35) Nishat Sameer(34) Vishal Kumar(40) Tejistha Pradhan(5) 6th Semester CIVIL ENGINEERING SIKKIM MANIPAL INSTITIUTE OF TECHNOLOGY
2. 2. Contents Introduction General description Brief history LIDAR platforms Types of LIDAR Basic Principle and techniques How LIDAR works LIDAR components Some example of LIDAR uses Applications Advantage Disadvantage Future Scope Conclusion
3. 3. INTRODUCTION 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 pulse to form an image.
4. 4. 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 infrared range of electromagnetic spectrum (i.e. 1064 nm). LIDAR instruments can rapidly measure the earths surface at sampling rates greater than 150 kHz. The resulting product is a densely spaced network of highly accurate geo-referenced elevation points/point cloud. It can be used to generate 3-D representation of earth surface.
5. 5. BRIEF HISTORY Searchlights were used to measure the altitude of clouds. Measurement was done by pointing a beam of light in sky and then reading the angle at which the beam light stuck the cloud. On a device that was a known distance away from the search light one was then able to obtain height by triangulation. First laser based searchlight was constructed by G.Fiocco at MIT using a ruby laser. From there the development of LIDAR sky rocketed.
6. 6. 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 collection of 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.
7. 7. TYPES OF LIDAR There are two basic types of LIDAR- Airborne LIDAR Terrestrial LIDAR
8. 8. Airborne LIDAR With airborne LIDAR, the system is installed in either a fixed-wing aircraft or helicopter. The infrared laser light is emitted toward the ground and returned to the moving airborne LIDAR sensor. There are two types of airborne sensors: Topographic LIDAR Bathymetric LIDAR
9. 9. Topographic LIDAR Topographic LIDAR can be used to derive surface models for use in many applications, such as forestry, hydrology, geomorphology, urban planning, landscape ecology, coastal engineering, survey assessments, and volumetric calculations.
10. 10. Bathymetric LIDAR Bathymetric LIDAR is a type of airborne acquisition that is water penetrating. Most bathymetric LIDAR systems collect elevation and water depth simultaneously, which provides an airborne LIDAR survey of the land- water interface. With a bathymetric LIDAR survey, the infrared light (traditional laser system) is reflected back to the aircraft from the land and water surface, while the additional green laser travels through the water column. Analyses of the two distinct pulses are used to establish water depths and shoreline elevations. Bathymetric information is very important near coastlines, in harbors, and near shores and banks. Bathymetric information is also used to locate objects on the ocean floor.
11. 11. Terrestrial LIDAR Terrestrial LIDAR collects very dense and highly accurate points, which allows precise identification of objects. These dense point clouds can be used to manage facilities, conduct highway and rail surveys, and even create 3D city models for exterior and interior spaces, to name a few examples. There are two main types of terrestrial LIDAR: Mobile LIDAR Static LIDAR
12. 12. Mobile LIDAR Mobile LIDAR is the collection of LIDAR point clouds from a moving platform. Mobile LIDAR systems can include any number of LIDAR sensors mounted on a moving vehicle. These systems can be mounted on vehicles, trains, and even boats. Mobile systems typically consist of a LIDAR sensor, cameras, GPS (Global Positioning System), and an INS (inertial navigation system), just as with airborne LIDAR systems. Mobile LIDAR data can be used to analyze road infrastructure and locate encroaching overhead wires, light poles, and road signs near roadways or rail lines.
13. 13. Static LIDAR Static LIDAR is the collection of LIDAR point clouds from a static location. Typically, the LIDAR sensor is mounted on a tripod mount and is a fully portable laser-based ranging and imaging system. These systems can collect LIDAR point clouds inside buildings as well as exteriors. Common applications for this type of LIDAR are engineering, mining, surveying, and archaeology.
14. 14. Basic Principles and Techniques 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 pulse. Time measurement is converted to a distance (i.e. the distance to the target and the position of airplane is then used to determine the deviation and location).
15. 15. Working of LIDAR-
16. 16. How LIDAR works Laser produces optical pulse. Pulse is transmitted, reflected & returned to the receiver. Receivers accurately measure the travel time. X,Y,Z ground coordinate can be calculated using : 1. Laser range 2. Laser scan angle 3. Laser position from GPS 4. Laser orientation form INS.
17. 17. COMPONENTS LIDAR has four components: Laser. Scanner and optics. LIDAR sensor and photo detectors. Position and navigation systems.
18. 18. Laser Airborne LIDAR systems use 1064nm diode pumped YAG lasers while bathymetric systems use 53 nm double diode pumped YAG lasers.
19. 19. 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 affects the angular resolution and range that can be detected.
20. 20. LIDAR sensors and Photodetectors The HDL-64E LIDAR sensor is designed for obstacle detection and navigation of autonomous ground vehicles and marine vessels. Its durability, 360 field views and very high data rate makes this sensor ideal for 3D mobile data collection and mapping applications. Two main photo detector technologies are used in LIDARS: 1. Solid state photo detectors(e.g.:- silicon avalanche photodiodes). 2. Photomultipliers.
21. 21. 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 usable data. For this, we have two techniques: GPS(Global Positioning System) IMU(Inertial Measurement Unit)
22. 22. Some examples of LIDAR use:
23. 23. Applications A LIDAR has the following main applications: Agriculture Biology and Conservation Wind farm optimization Law enforcement
24. 24. Agriculture LIDAR can be used to help farmers determine which areas of their fields to apply costly fertilizer to achieve highest crop yield. It can create a topographical map of the fields and reveals the slopes and sun exposure of the farm land.
25. 25. Biology and Conservation LIDAR has also found many applications in forestry. Canopy heights, biomass measurements & leaf area can all be studied using LIDAR systems. It is also used by many industries, including Energy, Railroad & the Department of Transportation as a faster way of surveying. Topographic maps can also be generated readily from LIDAR.
26. 26. Wind farm optimization LIDAR can be used to increase the energy output from wind farms by accurately measuring wind speeds and wind turbulence. An experimental LIDAR is mounted on a wind turbulence rotor to measure oncoming horizontal winds, and proactively adjust blades to protect components and increase power.
27. 27. Law enforcement LIDAR speed guns are used by the police to measure the speed of vehicles for speed limit enforcement purposes.
28. 28. Advantages The other methods of topographic data collection are land surveying, GPS, interferometry & photogrammetry. LIDAR technology has some advantages in comparison to these methods listed below: Higher Accuracy Fast Acquisition and Processing Minimum human dependence- As most of the processes are automatic unlike photogrammetry, GPS or land surveying.
29. 29. Weather/Light Independence- Data collection independent of sun inclination and at night and slightly bad weather. Canopy Penetration- LIDAR pulses can reach beneath the canopy thus generating measurements of points there unlike photogrammetry. Higher data density- Up to 167,000 pulses per second. More than 24 points per meter sq. can be measured in multiple returns to collect data in 3D. Cost- It has been found by comparative studies that LIDAR data is cheaper in many applications. This is particularly considering the speed, accuracy & density of data.
30. 30. Disadvantages High operation costs (Rs. 10 Lacs /hour). Ineffective during heavy rain and/or low cloud/mist. Degraded at high sun angles and reflections. Latency data not processed locally. Unreliable for water depth(