lidar introduction @ #dataweekend

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LIDAR技術與應用介紹 © LIDAR Tech. Co.,Ltd., 2013

LiDAR技術與應用介紹

徐偉城

2013-10-05



Mapping

• Surface(ground, water) -> Airborne -> Spaceborne

• Sketch -> Analog -> Digital

• Digital Map

– Vector(Google Map地圖)

– Raster(Google Map衛星)

– 3D (Google Earth)

– …

2



Elevations on Map

• Features(point, line, polygon)

– Color, Shadow, …

• Contour

• DTM(Digital Terrain Model, Digital Topography Model)

– DEM(Digital Elevation Model)

– DSM(Digital Surface Model)

– DBM(Digital Building Model)

– …

3



DTM for Digital Map

• DTM Quality

– Resolution(grid size)

– Precision

– Efficiency

• Methods of DTM

– Ground survey

– Stereo Image processing(Photogrammetry, Satellite)

– Synthetic Aperture Radar(SAR)

– LiDAR

• Airborne LiDAR provides high quality DTM

4



DEM Comparison 5

5m grid 1m grid



What is LiDAR

• LiDAR(Light Detection And Ranging, Lidar, 光達)

– Laser

– Range Finder

– Scanner

• Various type of LiDAR(Laser Scanner)

– Handheld： 3D Scanner

– Desk：3D Scanner & Printer

– Ground：Terrestrial LiDAR

– Mobile Mapping System(car, ship, …)

– UAV & Airborne LiDAR

– Satellite LiDAR

– *Atmosphere LiDAR

6



LiDAR on Different Platforms

• Ground

• Car

• Ship

• UAV

• Airborne

7



GPS Satellite GPS Satellite

GPS X

Z

Y

IMU

Roll

Heading

Pitch

GPS Base Station

EDMI

Aircraft position

(lat , lon , el)

GPS

Aircraft orientation

(roll , pitch , heading)

IMU

Range and angle

EDMI +

=

(E , N , h …)

Point cloud

Components of Airborne LiDAR

POS(position and

orientaion system)



Airborne LiDAR Characteristics

• Dense Point

– 1 pt/m2 to 10pt/m2 (sometimes higher)

– Multiple Returns with Intensities

– Full Waveform

• Accurate

– Penetrate Vegetation

– Vertical:5~15cm

– Horizontal:15~50cm (depend on fly height)

• High Efficiency

– High efficiency of data acquisition and processing

– Fewer GCPs

– Filtering without measuring

• Standard Data Format

– Las file (by ASPRS)



Different Point Density

density=10 pts/m2

density=1 pts/m2 density=2 pts/m2

density=5 pts/m2



Data Acquisition

Trajectory

Strip adjustment

Aerial Photo

Combined Separation Satellite Lock/Elevation



Ground Points Filtering

12

Automatic classify and manual editing

Correct

Error (canopy)

Error (mountain ridge)



P.13

Flight lines Intensity Classes

Echos Elevation Waveform

Attributes of Point Cloud



DEM/DSM Products

14

DEM

DSM



DEM/DSM Products

DSM shaded relief DEM shaded relief



Laser Footprint

Start Pulse

Range and Intensity Measurement

Range 1

Range 2

Range 3

Intensity 1

Intensity 3

Intensity 2

Discrete & Full Waveform LiDAR

LiDAR Returns(Leica, 2004,2010)

Full Waveform Digitizer

T1 , I1

Tn , In

• Laser – Wave length：1064 nm

– Power：2~4 watt

– Beam Divergence：0.25 ~0.8 mrad

– Pulse Rate：50~200 kHz

– Classification：Class IV



Advantages of Full Waveform LiDAR

17

Discrete Las Full Waveform Las



空載光達產製數值高程模型技術介紹



About LIDAR Technology Co. Ltd.

• Earth Observations

Spaceborne, Airborne & Terrestrial Data Acquisition

– Photogrammetry and LiDAR

– Hyper-spectrum and Thermal Image

• Geo-informations

Value-added products and applications

– Image Mapping and Interpretation

– Various DEM/DSM Products (90m, 30m, 10m, 5m, 1m, 0.1m)

– Historical Image and Topography Services

• Location Based Services

RS/GIS/GPS Development & Consultant Service

– 3D Building Model

– Disaster Applications

– Augmented Reality



P.20

Thank you

TEL: 886-3-6589495

MAIL: [email protected]

台北101大樓點雲剖面圖台北101大樓模型(Google Earth)