Laser scanning - Metla · • Laser scanning since 1997 • Digital aerial photography since 2005...
Transcript of Laser scanning - Metla · • Laser scanning since 1997 • Digital aerial photography since 2005...
LASER SCANNING
Pekka Savolainen
© BLOM Kartta Oy 2007
CONTENTS
• BLOM Group
• Airborne laser scanning - introduction
• Other remote sensing data sources
• ALS based forest inventory
• Conclusions
BLOM Group
• Largest remote sensing company in Europe• Listed in Oslo exchange• Offices in 11 countries, 900 employees• Blom operates 33 planes, 4 helicopters, 9 ALS, 9 Digital
Aerial Camera, 1 hyperspectral sensor, 55 Pictometry cameras
• Forestry activities in Finland, Norway, Sweden ja Spain
Blom’s pan-European oblique mosaic database
Blom offices in Europe
Blom offices / subsidiaries in Europe
BLOM BUSINESS AREAS
Databases -Pictometry
Mapping and modelling
Aerial photo Laser Scanning
Database applications
BLOM KARTTA AND FORESTRY
• Infrared aerial photography since 1977
• Colour infrared (CIR) since 1977
• Digital forest orthophotos since 1995
• Laser scanning since 1997
• Digital aerial photography since 2005
• ALS based forest inventories since 2006
AIRBORNE LASER SCANNING - INTRODUCTION
• Active measurement – no sunlight required• Enabling technologies: laser ranging and satellite/inertial
positioning• Airplane or helicopter
BASIC PRINCIPLE
• Sensor measures bearing and range 33000 – 167 000 times every second
• Location and attitude from satellite and inertial navigation• A swath is covered as airplane advances• A point cloud is produced by computer processing
POINT DISTRIBUTION AND DENSITY
• Point density on ground is determined by:– pulse repetition frequency (PRF)– flight altitude– scanning angle (FOV)– flying speed, ~75 m/s (270 km/h)
• Point distribution is adjusted by– scanning angle– scanning frequency
• Typical values:– 2000 m altitude– 70 000 Hz PRF– 30 degrees FOV– 1070 m swath width– 35 Hz scanning frequency– 1.07 m x 1.07 point distribution– 0.9 points/sq.meter
OPTECH ALTM GEMINI
• BLOM Geomatics (Norway) operates in Northern Europe
SOME OPTECH GEMINI HIGHLIGHTS
• Pulse rep. frequency: 33 – 167 kHz• Operating altitude: 80 – 4000 m• Horizontal accuracy: H/11000• Elevation accuracy: 5 – 10 cm typical• Up to 4 return pulses
SOME ALS APPLICATIONS
• Digital Terrain Models (DTM)– DTM for construction of roads, railways, power plants, power
lines, pipelines, etc
• Digital Surface Models (DSM)– Telecom planning– 3D city models
• Powerline inspection• Forestry
OTHER REMOTE SENSING DATA SOURCES
• AERIAL PHOTOGRAPHY– ANALOGUE (FILM) CAMERAS– DIGITAL AERIAL CAMERAS
• SATELLITE IMAGERY– AVAILABILITY AND PRICE
• HYPERSPECTRAL AND SAR
BLOM FORESTRY
• Production chain:– planning– aerial photography– laser scanning– sample plot measurement– modelling and interpretation– delivery to customer database
• Pilot project 2006
• Commercial production started 2007
ALS BASED METHODS
• SINGLE-TREE METHODS– high point density– canopy segmentation or maximum seeking
• AREA BASED REGRESSION METHODS– low point density– square grid
• AREA BASED NON-PARAMETRIC METHODS– low point density– grid or segment as basic area– k-NN (Nearest Neighbour)– k-MSN (Most Similar Neighbour)
FORESTRY VARIABLES
• ALL VARIABLES WANTED:
• basal area• volume• mean DBH• mean height• stem count
• diameter distribution• age• …
1
2
ACCURACY
• PILOT 2006:– basic variables: 10-15 %– by species: 50–80 %
• PRODUCTION 2007– basic variables: 10 %– by species: 30 %
PRODUCTION VOLUME AND CAPACITY
• 2006: 60 000 ha
• 2007: 200 000 ha
• 2008: 2000 000 ha
CONCLUSIONS
• ALS BASED METHODS ARE HERE NOW
• ALS + DIGITAL PHOTO: A PERFECT COUPLE
• ACCURACY IS OPERATIONALLY VIABLE
• ALS IS COST EFFICIENT
• THE METHODS ARE DEVELOPING RAPIDLY