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

THANK YOU FOR YOUR ATTENTION

• QUESTIONS?

• Additional information: pekka.savolainen@blomkartta.fi