CHAPTER 8 LIDAR Light Detection and Ranging (Remote Sensing System)

CE 316 March 2012

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8.1 Introduction LIDAR: Laser Detection And Ranging Defined: LIDAR (Light or laser Detection and Ranging) is an optical remote

sensing technology that measures properties of scattered light to find range and/or other information of a distant target (i.e. collect topographical data)

Defined: LADAR (Laser Radar) used in military context. LADAR uses laser beams to scans and process the signal echoed from targets, to create a . The LADAR processor looks for in the scenes. The processor continuously compares these patterns with 3D targets files stored in the weapon's memory. The primary difference between LIDAR and laser radar is that with LADAR, much wavelengths of the electromagnetic spectrum are used, typically in the ultraviolet, visible or near infrared. Speed detection?

Laser view of Scud mobile launcher hidden between two trucks.

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8.2 Background 

Many names of LIDAR - Laser Altimetry, airborne laser scanning, and airborne laser terrain mapping



Spatial Data Collector - Collects data from a small aircraft via laser scanner, Global Positioning System (GPS) and

 Data Use - Digital elevation maps (DEM)

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8.3 LIDAR For Terrain Mapping 8.3.1 History



Airborne Laser Terrain Profiler, Penny (1971)



Advances:

• • • •



GPS (DGPS) IMU

Ground based LiDAR

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8.3 LIDAR For Terrain Mapping 8.3.2 What is Lidar and how does it work  A typical LIDAR system rapidly transmits

that

reflect off the terrain and other objects.

 The return pulse is converted to electrical impulses and collected by a high-speed data recorder.

 Since the formula for the speed of light is well known, time intervals from transmission to collection are easily derived.

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8.3 LIDAR For Terrain Mapping 8.3.3 Components of LIDAR22

Typical LiDAR components (Wehr and Lohr, 1999)

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8.3 LIDAR For Terrain Mapping 8.3.4 Components of LiDAR22 A basic LIDAR system involves a laser range finder reflected by a rotating mirror (top). The laser is scanned around the scene being digitized, in one or two dimensions (middle), gathering distance measurements at specified angle intervals (bottom).

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11.3 LIDAR for Terrain Mapping 11.4.3 Pitch 11.4.4Roll Yaw 8.3.5 11.4.3 Roll

Pitch (http://www.nasm.si.edu/exhibitions/gal109/NEWHTF/HTF541B.HTM)

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11.4 Using LIDAR  Active Sensor - Sun independent, can conceivably be used 24/7 (Wehr and Lohr, 2005)



Limited by weather conditions (Li and Baker, 2003)



Season

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8.4 Using LIDAR 8.4.1 Limits



Rain and fog

• 

High density vegetation

•

Forest cover ≥ 80% result in low density ground points

• 

Terrain Slope

•

Errors increase with sloped land 283

8.4 Using LIDAR 8.4.2 Terrain



Most terrain can be mapped with LIDAR



Water

• • 

Generally near infra-red lasers (most common) can not be used Blue/green laser (penetrates up to 50m)

Sloping terrain

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8.4 Using LIDAR 8.4.3 Average Scanning Values

Average values from a typical LiDAR Scan (reproduced from Elsheimy et al. 2005)

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8.4 Using LIDAR 8.4.4 Constant Velocity Rotating Mirror Scanning

Constant velocity rotating mirror scanning technique (El-Sheimy et al., 2005) 286

8.4 Using LIDAR 8.4.5 Oscillating Mirror Scanning

Oscillating mirror scanning technique (El-Sheimy et al., 2005) 287

8.4 Using LIDAR 8.4.6 Fibre Optic Scanning

Fibre optic scanning technique (El-Sheimy et al., 2005)

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8.4 Using LIDAR 8.4.7 Elliptical Scanning

Elliptical scanning technique (El-Sheimy et al., 2005) 289

8.4 Using LIDAR 8.4.8 Coordinates



Geo-referenced data (x,y,z)

•

•

In North America, references the NAD 83

One ground control station is needed within 30km of the project site (NCGC Report EM 11101-1000, 2002)

•

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8.4 Using LIDAR 8.4.9 Equipment Providers

Optech ALTM 3100EA http://www.optech.ca/prodaltm.htm

Falcon II equipment http://www.toposys.com/

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8.4 Using LIDAR 8.4.10 LIDAR Vendors



LiDAR Worldwide vendors (NCGC Report EM 1110-1-1000, 2002)

•

1995 (3)

•

2000 (50)

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8.4 Using LIDAR 8.4.11 Major Canadian Consultant



LiDAR Services International Inc., Calgary, AB.

•

Projects:  Highway corridor survey (Sask. Highways)  4 new Uranium Mine Sites, Northern Sask.

 Many in Alberta, Manitoba, US, etc.  Multiple projects on 5 continents

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8.4 Using LIDAR 8.4.11 Major Canadian Consultant

 Offices: Houston, Calgary and Ottawa  Projects: • Oil and Gas • Land Development • Power-line and Pipeline • Transportation • Mining • Flood Plain

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8.4 Using LIDAR 8.4.12 How much?

Cost versus vertical accuracy (Li and Baker, 2003)

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8.4 Using LIDAR 8.4.12 How much?



NOAA Coastal Services Center

•

$1000 to $2000 US per Mi2

•

Includes:  Flight  Data collection

 Post-processing  Delivery

•

Dependant on location and specifications

(NOAA Coastal Services Centre, 2006) http://www.csc.noaa.gov/crs/rs_apps/sensors/lidar.htm#cost

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8.4 Using LIDAR 8.4.13 Applications

        

Coastline protection Floods City Models

Nature Conservation

Open pit and deposits Corridor mapping

Research

These data are collected with aircraft-mounted lasers capable of recording elevation measurements at a rate of 2,000 to 5,000 pulses per second and have a vertical precision of 15 centimeters (6 inches). After a baseline data set has been created, follow-up flights can be used to detect shoreline changes. 297

8.4 Using LIDAR 8.4.13 Applications LiDaR 3D Screen Shot

• Manitou Beach Road Section 1 Scan 2

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8.4 Using LIDAR 8.4.13 Applications • Manitou Beach Road Scan Near Danceland LiDaR 3D Screen Shot

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8.4 Using LIDAR 8.4.14 Products Digital Surface Model (DSM) (Earth’s surface including objects)

Digital Terrain Model (DTM) (Earth’s Surface only)

Döbern redevelopment area © eta AG, Germany

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8.4 Using LIDAR 8.4.14 Products

Digital Terrain Model (DTM)

Relief image of Celtic chieftain’s settlement Heuneburg

3D presentation of Roman fortified camp Cava de Viriato near Viseu, Portugal

http://www.toposys.com/joomla/index.php?option=com_content&view=article&id=63&Itemid=92&lang=en

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8.4 Using LIDAR 8.4.14 Products

Point cloud model

REF: Point cloud with errors removed (www.toposys.com, 2006)

http://www.toposys.com/joomla/

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8.4 Using LIDAR 8.4.15 Cases



Gutelius (1998)

•

Successful applications in highway engineering, coastal

mapping and corridor mapping for power lines (500600km per day)



Berber and Shortridge (2005) and Webster and Dias (2005)

•

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8.5 Discussion 

Terminology

•

Create an industry and academic

standard



Industry versus Academia

• 

Is the data up to the required standards

Appropriate applications

•

LiDAR is the most accurate remote sensing technology, use it appropriately and when necessary

REF: http://www.toposys.com/joomla/

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