Post on 02-Jun-2018
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PRINSIP ALAT LiDAR
JARAK = ( Laju cahaya x Masa ) / 2
Pengukur Jarak Laser (Cahaya)
Teknologi ini menggunakan cahaya laser. Ia dapat mengukur
jarak dengan mengukur ketumpatan cahaya laser yang
dibalikkan. Dengan menggunakan asas matematik, kedudukan
sesuatu jarak dapat diketahui dengan persamaan di bawah :
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PENGEN L N teknologi LiD R
LiDAR adalah satu kaedah pengukuran ketinggian para
mukabumi dengan menggunakan teknologi laser
Satu sistem penderiaan aktif, boleh menembusi awan
nipis
Data asas yang telah diortorektifikasi
Mengatasi masalah kelewatan pengukuran titik kawal
bumi
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LIDAR ACCURACYVertical
better than 15 cm at 1,200 m
better than 35 cm at 3,000 m
Horizontal
better than 1/2,000 x altitude
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PERB NDING N RINGK S FOOTPRINT
D N G RIS PENERB NG N
Camera and lens
Type
Image Size
(mm)
Focal Length
(f) (mm )
Field of
View
(degree
)
Image Scale at
1000m flying
height (H)
(f/H)
Footprint at
1000m flying
height
(meter)
No. of
f l ight
l ines for
30x30km
and 30%
sidelap
RC 30 Narrow 230 x 230 600-610 30-35 1:1666 383.2 x 383.2 111
RC 30 Normal 230 x 230 300-305 60-80 1:3333 766.6 x 766.6 56
RC 30 Wide 230 x 230 150-153 90-95 1:6666 1533.2 x 1533.2 28
RC 30 Super wide 230 x 230 85-88 120-130 1:11764 2705.7 x 2705.7 16
ALTM-DCS
37 x 37
(4077x4092
pix) 55 36
1:18181
(*GSD=0.163m) 667.1 x 669.6
66
ALSS- ALTM 3070 - -
50
(max) -
932.6
(swath width)
46
*GSD = Ground Sample distance
= pixel size x im age scale factor
= 0.009 mm x 18181
= 0.163m
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2ndReturn
3rdReturn
2ndReturn
3rdReturn
1stReturn
Last Return
Pulse Rate Frequency(PRF)
First-pulse Mengukur jarak bagi objek pertama
yang dipantulkan.
Contoh disebelah menunjukkanpantulan cahaya pada pokok dan tanahdisekitarnya.
Last-pulse Mengukur jarak bagi objek terakhir
yang dipantulkan. Contohnya seperti bangunan, tanah,
pokok, bukit, air dan sebagainya.
Bersambung
PRINSIP LiDAR
(1) Pantulan Laser
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4 PANTULAN LASER
YANG DIAMBIL
1stReturn
Last Return3rdReturn
2ndReturn
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PRINSIP PANTULAN LiDAR
Altitude (km) Hz< 1.5 < 70,000
< 2.0 < 50,000
< 3.0 < 33,000
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CIRI-CIRI PANTULAN LiDAR
Highly Reflective Materials = Strong Return
Signal
Faktor-faktor Yang Mempengaruhi Pantulan : Ketinggian (Elevation)
Kandungan (Composition)
Kepadatan (Density)
Orientasi/Kedudukan ke sensor (Orientation to thesensor)
High Reflectivity: Permukaan Tanah Cerah
Rumput
Pokok
Air (berombak/ bergerak)
Low Reflectivity: Permukaan TanahGelap
Tanah Hitamspt.Tar, Tanah
Berturapdll (Asphalt)
LombongBatuArang(Coal)
Permukaan Basah (Wet surface) Kasawan Berlumpur (Mud)
Air(tidak berombak)
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PRINSIP LiDAR
( 2 ) Scanning
Depending on the laser altimeter used and the altitude of operationabove ground spot sizes of 20 cm (8") to 25 m (85 ft) and strip widths of
50 m
(150 ft) to 9 km (6 mi) can be achieved.
o Scan Rate: < 70 Hz
o FOV: < 25 (Half Angle)
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Laser Foot Print Narrow beam
divergence
Spread of laser
limits accuracy iflaser spot on
ground gets too
large
Spot sizes of 5 30 cm are useful
and necessary for
canopy
penetration
D = H*a
Where:
D = Spot Size
H = Height
a = Beam
Divergence
Angle in Radius
D
Ha
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LiDAR MENGGUNAKAN AIRBORNE LASER SCANNING SYSTEM (ALSS)
LiDAR menggabungkan tiga teknologi canggih iaitu :
Kedudukan kapalterbang ditentukan menggunakan teknologi
penentuan titik sejagat/ kedudukan(Global Positioning System:
GPS). Keadaan/orientasi kapalterbang (Yaw, Pitch and Roll) semasa
pengukuran
direkodkan menggunakan sistem INS (Inertial Navigation System) /
IMU
(Inertial Measurement Unit), Jarakdari ALSS ke mukabumi di ukur menggunakan laser
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Ketiga tiga data ini kemudiannya digabungkan untuk menghitung koordinat
mukabumi dalam 3 dimensi.
Ketepatan yang dapat diperolehi menggunakan teknologi ini dilapurkan
sebanyak +/- 15cm bagi satah pugakdan =/- 0.5 m bagi kedudukan
mendatar
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LiDAR(ALSS-Airborne Laser Scanning System & DCS-Digital Camera
System)Combined
Computer Rack
Sensor Head
Operator &Flight
Navigation
InterfaceLaptop
(1)
(2)
(3)
(4)
Digital Camera
(5)
ALSS
DCS
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LiDAR basic output
( 2 ) Digital Image
( 1 ) Laser Points
Digital images of Cameron Highlands
Laser points of Cameron Highlands
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Produk LiDAR
(1) Data Intensity
4000 shades of Gray ScaleRecorded at all flight altitudes
(2) Bahagian Ketinggian (Shaded Relief)
(3) Kontur
(4) Grid/TIN
(6) Ortofoto**
(5)DTM/DE
M
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APLIKASI DATA LiDAR
( 1 ) Urban Survey( 2 ) Power Line Mapping
( 3 ) Flood Simulation
( 4 ) Vegetation Removed
( 5 ) Forestry & Biomass Estimates
( 6 ) Coastal Areas : Erosion
Monitoring
( 7 ) Flood Study( 8 ) Disaster Assessment
( 9 ) Urban Mapping
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( 1 ) Urban SurveyDowntown Toronto
Ortofoto & Kadester Lot
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( 2 ) Power Line MappingCanada
Route assessment
Vegetation encroachment assessmentPrevention of accidental power line cut-off
Electrical load assessment
Forest fire preventionSafety assessment
( 6 ) E si
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1998199920002001
( 6 ) ErosionMonitoring
Coastal Areas
Erosion area
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( 8 ) Disaster AssessmentTaiwan
LiDAR C & P ssi Ti Esti ti
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Assumptions :
Flying Ht : 1000 m (~3300 ft)
Speed : 100 knots (~50m/sec)
Field Of View : 37o
Swath Width : 669 m
Flying Times : 1 hour
Estimation :
Unclassified Processing Time : 120 sq km/hour
Laser Points Processing Time : 8-12 hours
LiDAR Coverage & Processing Time Estimation
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Sensors
Laser +
Receiver
System
GPS/IMU
Digital Imaging
System
Post-Processing
Laser Pulse
Range Data
Lat, Long, Height,
Roll, Pitch, Heading
Digital Images(TIFF, JPEG, IMG)
Output
LAS(LIDAR Point
Data Records)
X, Y, Z point data
Geo-Referenced
Image (GeoTIFF)
Raw
Data
Processed
Data
Intensity
MeasurementFeature Classification
Aided by Intensity Measurement
ALSS d DCS P i
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ALSS and DCS Processing
Overview
POSPAC
Airborne & Base
Station GPS Processing
SBET Files Processing
Blending GPS & IMU Data
REALM
Importing a BETDefine Polygon
Processing Laser Points
Defining Processing Area
Combining Laser Points
Output Laser Points
(First and last pulse an Intensity)
TERRASCAN
Clean DataClassification
Manually QC Clean
Geoid Correction
Surface
Contour
TERRAMODELLER
Lattice Grid
Contour Editting
Point Cloud
DEM
ALSS
(Airborne Laser Scanning System)
ORTHOPRO (ISAT)
Create Project
Setup Camera With IO Parameters
Drag In Images Import EO File
Ortho Rectification
Seam Line Generation
IMAGEVUE / IMAGEMISSION
Downloading
Developing
RGB
Dark and Gain Correction
Image View
REALM
ALTM System
ALTM Tapes
Decoding Tapes
Creating a Database
Adding a Database
PRODUCTS
DEM
Contour
PRODUCTS
Orthophoto
SBET File Output
ISAT Ready ImageDCS
(Digital Camera System)
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SYNTHETIC APERTURE RADAR (SAR)
Satellite-based, stereo SAR processing
Data source: RadarSat 1
Acquired in 2003 DEM and orthorectified imagery by Q4,
2003
DEM Accuracy: 25 m
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SYNTHETIC APERTURE RADAR (SAR)
SAMPLE IMAGE
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SYNTHETIC APERTURE RADAR (SAR):
PRODUCTS
DEMOrthoimage