Considerations for Planning, Acquiring, and Processing LIDAR Data for Forestry Applications University of Washington-Precision Forestry Cooperative Pacific.

Considerations for Planning, Considerations for Planning, Acquiring, and Processing LIDAR Acquiring, and Processing LIDAR

Data for Forestry Applications Data for Forestry Applications

University of Washington-Precision Forestry CooperativeUniversity of Washington-Precision Forestry CooperativePacific Northwest Research Station-Silviculture and Forest Models TeamPacific Northwest Research Station-Silviculture and Forest Models Team

Robert J. McGaugheyRobert J. McGaugheyUSDA Forest Service--PNW Research StationUSDA Forest Service--PNW Research Station

Hans-Erik AndersenHans-Erik AndersenUniversity of Washington-Precision Forestry CooperativeUniversity of Washington-Precision Forestry Cooperative

Stephen E. ReutebuchStephen E. ReutebuchUSDA Forest Service--PNW Research StationUSDA Forest Service--PNW Research Station


OutlineOutline

Brief LIDAR overviewBrief LIDAR overview LIDAR data characteristics & deliverablesLIDAR data characteristics & deliverables QA/QC proceduresQA/QC procedures Data processingData processing Introduction of FUSION softwareIntroduction of FUSION software ConclusionsConclusions


LIDARLIDAR

Light Detection and RangingLight Detection and Ranging 4 types4 types

AtmosphericAtmospheric Continuous waveformContinuous waveform Discrete return (profiling)Discrete return (profiling) Discrete return (scanning)Discrete return (scanning)

Airborne Laser Scanning (ALS)Airborne Laser Scanning (ALS) Discrete return (scanning) mounted on aircraftDiscrete return (scanning) mounted on aircraft


ALS System ComponentsALS System Components

Scanning laser Scanning laser emitter-receiver unitemitter-receiver unit

Differentially-Differentially-corrected GPScorrected GPS

Inertial measurement Inertial measurement unit (IMU)unit (IMU)

Computer to control Computer to control the system monitor the system monitor mission progressmission progress

Interesting targetsInteresting targets


Multiple ReturnsMultiple Returns

Many laser systems can record several Many laser systems can record several returns for each pulsereturns for each pulse

Multiple returns occur when the laser Multiple returns occur when the laser beam is only partially blockedbeam is only partially blocked

Part of the laser energy is reflected back to Part of the laser energy is reflected back to the sensorthe sensor

The remaining laser energy continues The remaining laser energy continues downwarddownward

Up to 5 returns per pulseUp to 5 returns per pulse Typically only 2-3 returnsTypically only 2-3 returns

Many systems record the amount of Many systems record the amount of energy reflected by target objectsenergy reflected by target objects

Intensity (near-infrared, 1064 nm)Intensity (near-infrared, 1064 nm)


Multiple ReturnsMultiple Returns

All returns (16,664 pulses)All returns (16,664 pulses)

11stst returns returns

22ndnd returns (4,385 pulses, 26%) returns (4,385 pulses, 26%)

33rdrd returns (736 pulses, 4%) returns (736 pulses, 4%)

44thth returns (83 pulses, <1%) returns (83 pulses, <1%)


Comparison With Other Remote Comparison With Other Remote Sensing TechnologiesSensing Technologies

Active sensorActive sensor Laser pulse is emitted and reflected energy is measuredLaser pulse is emitted and reflected energy is measured Passive systems rely on reflected solar energyPassive systems rely on reflected solar energy

Returns are actual measurementsReturns are actual measurements Range is computed based on round-trip travel time for Range is computed based on round-trip travel time for

laser energylaser energy Combined with accurate aircraft position and attitude to Combined with accurate aircraft position and attitude to

produce XYZ point measurementproduce XYZ point measurement Small footprint at targetSmall footprint at target

30-100 cm footprint at ground surface30-100 cm footprint at ground surface 4+ pulses/m4+ pulses/m22 is common is common Multiple returns over porous targetsMultiple returns over porous targets


LIDAR AccuracyLIDAR Accuracy

RMSE provided by LIDAR system RMSE provided by LIDAR system manufacturersmanufacturers 10-15cm vertical10-15cm vertical 50-100cm horizontal50-100cm horizontal

Several studies provide independent Several studies provide independent verification of these valuesverification of these values Ground survey pointsGround survey points Tree heightsTree heights Building heightsBuilding heights Alignment of power transmission linesAlignment of power transmission lines


LIDAR DEMLIDAR DEM

Mean LIDAR DEM errorMean LIDAR DEM error 22 cm…9-inch field boot 22 cm…9-inch field boot

height!height!

Maximum errors:Maximum errors: +1.3 meter, -0.63 +1.3 meter, -0.63

meter…(+4.3 ft, -2.1 ft)meter…(+4.3 ft, -2.1 ft)

Error is not Error is not significantly affected significantly affected by canopy densityby canopy density

Bare-Earth AccuracyBare-Earth Accuracy


LIDAR Data CharacteristicsLIDAR Data Characteristics

High spatial resolutionHigh spatial resolution Typical density is 0.5-6 pulses/mTypical density is 0.5-6 pulses/m22

2-3 returns/pulse in forest areas2-3 returns/pulse in forest areas Surface/canopy models typically 1-5m gridSurface/canopy models typically 1-5m grid

Large volume of dataLarge volume of data 5,000-60,000 pulses/hectare5,000-60,000 pulses/hectare 12,500-150,000 returns/hectare12,500-150,000 returns/hectare 0.3-3.6 Gigabyte/hectare0.3-3.6 Gigabyte/hectare


““Typical” Mission SpecificationsTypical” Mission Specifications

Topographic Topographic mappingmapping

Vegetation Vegetation mappingmapping

Scan angleScan angle ±±20 20 °° ±±12 12 °°

Flying heightFlying height 2200 m2200 m 1200 m1200 m

Pulse ratePulse rate 10-70 kHz10-70 kHz 30-100 kHz30-100 kHz

Beam footprintBeam footprint 66 cm66 cm 36 cm36 cm

Swath widthSwath width 1600 m1600 m 510 m510 m

Pulse spacingPulse spacing 1-3 m1-3 m 0.2-0.8 m0.2-0.8 m


Deliverables:Deliverables:General ConsiderationsGeneral Considerations

Delivery formatDelivery format Return data, surfaces, images, GIS coveragesReturn data, surfaces, images, GIS coverages Can you read the format?Can you read the format? Does the data contain all the information you need?Does the data contain all the information you need?

Delivery mediaDelivery media External hard drives are common but not easy to backup to more External hard drives are common but not easy to backup to more

stable mediastable media You would like to be able to retrieve single data files from your backupYou would like to be able to retrieve single data files from your backup

What do you do with multiple DVDs?What do you do with multiple DVDs? How do you know what has been delivered?How do you know what has been delivered?

Contracts need to include specific deliverables to help you assess Contracts need to include specific deliverables to help you assess overall data quality and completenessoverall data quality and completeness

Deliverables based on the actual data…not just coverage area Deliverables based on the actual data…not just coverage area boundariesboundaries

Do you have adequate storage space to move data onto faster Do you have adequate storage space to move data onto faster devices?devices?

Disk spaceDisk space BandwidthBandwidth


Deliverables:Deliverables:Common Data ProductsCommon Data Products

MetadataMetadata Flight informationFlight information LIDAR system settingsLIDAR system settings Data coverageData coverage

Bare ground productsBare ground products Bare-ground returnsBare-ground returns Surface modelsSurface models

Return dataReturn data Coarse filtering to remove outliersCoarse filtering to remove outliers Includes return numberIncludes return number

Always get the return data for a projectAlways get the return data for a project Adds very little to contract costAdds very little to contract cost Will cost you $$ if you decide you want it laterWill cost you $$ if you decide you want it later


Deliverables:Deliverables:Forestry-Specific ProductsForestry-Specific Products

Canopy height modelsCanopy height models Normalized using bare-ground surfaceNormalized using bare-ground surface Filtered to remove buildings, powerlines, and other Filtered to remove buildings, powerlines, and other

above-ground featuresabove-ground features Canopy cover mapsCanopy cover maps

Presence/absence of vegetationPresence/absence of vegetation Vegetation density (percent cover)Vegetation density (percent cover)

Geo-referenced LIDAR intensity imagesGeo-referenced LIDAR intensity images First return intensity value (reflected energy)First return intensity value (reflected energy) Useful an “image” (B/W IR image)Useful an “image” (B/W IR image) Useful as a layer for further analysisUseful as a layer for further analysis


QA/QC Assessment:QA/QC Assessment:Did you get what you ordered?Did you get what you ordered?

Initial delivery:Initial delivery: Missing dataMissing data Missing returnsMissing returns Misclassified returnsMisclassified returns Tile naming inconsistenciesTile naming inconsistencies

Contractor used custom software to Contractor used custom software to produce ASCII formatted dataproduce ASCII formatted data

Several flight lines were omittedSeveral flight lines were omitted They had no way to view the ASCII filesThey had no way to view the ASCII files They didn’t know what they deliveredThey didn’t know what they delivered

Over 60 client-hours to sort out the Over 60 client-hours to sort out the problemsproblems

Contractor made 3 deliveries over a 5-Contractor made 3 deliveries over a 5-week periodweek period


QA/QC Assessment:QA/QC Assessment:Quality and CompletenessQuality and Completeness

Total project areaTotal project area 47,818 ha47,818 ha

(118, 111 acres)(118, 111 acres)

Total returnsTotal returns 2.9 billion2.9 billion

Total file storage space Total file storage space (LAS binary format)(LAS binary format)

77 Gb77 Gb

Data tiles (processing bins)Data tiles (processing bins) 277277

Tile sizeTile size 1 km wide by 2 km tall1 km wide by 2 km tall

(200 ha)(200 ha)

HTML report generated by FUSION-CatalogHTML report generated by FUSION-Catalog


Data Processing:Data Processing:What do I do with all these points?What do I do with all these points?

Raw data are interesting to look at Raw data are interesting to look at but require extensive processing to but require extensive processing to

create useful informationcreate useful information

Raw data are interesting to look at Raw data are interesting to look at but require extensive processing to but require extensive processing to

create useful informationcreate useful information


Data Processing:Data Processing:Bare-Earth Surface ModelBare-Earth Surface Model


Data Processing:Data Processing:Canopy Surface ModelCanopy Surface Model


Final Products:Final Products:Canopy Height (Raw Data)Canopy Height (Raw Data)


Final Products:Final Products:Percent Cover (2.5m grid)Percent Cover (2.5m grid)


Final Products:Final Products:LIDAR Intensity Image (5m grid)LIDAR Intensity Image (5m grid)

1m 1m gridgrid


Coniferous/Deciduous Classification Coniferous/Deciduous Classification Using Intensity Values (Raw Data)Using Intensity Values (Raw Data)


FUSION SoftwareFUSION Software

Sample optionsSample options•Shape & sizeShape & size•Coloring rulesColoring rules•Snap to POISnap to POI

LDVLDV

DataDataviewerviewer

ColorColor

LightingLighting GlyphGlyph

MotionMotion

MeasurementMeasurement

FUSIONFUSION

DataDatainterfaceinterface

ImageImage

LIDAR dataLIDAR data

Points of interest (POI)Points of interest (POI)

Bare-earth modelBare-earth model

HotspotsHotspots

Canopy modelCanopy modelTree dataTree data

PDQPDQ

Simple DataSimple Dataviewerviewer

Command line Command line processing and processing and utility programsutility programs


FUSION SoftwareFUSION Software

Displays several kinds of dataDisplays several kinds of data Allows users to interactively select portions of Allows users to interactively select portions of

large datasets for viewinglarge datasets for viewing Users can “mine” the data to discover new informationUsers can “mine” the data to discover new information

Clips all data layers and makes them available for Clips all data layers and makes them available for detailed 3D viewingdetailed 3D viewing

Supports stereoscopic viewingSupports stereoscopic viewing Runs on a current hardwareRuns on a current hardware

Available through RSAC…included on DVD you Available through RSAC…included on DVD you were given at registration…demos on Thursdaywere given at registration…demos on Thursday


Main System componentsMain System components

FUSION – 2D interface to several data typesFUSION – 2D interface to several data types Allows extraction of data subsetsAllows extraction of data subsets Interacts with LDV to display samplesInteracts with LDV to display samples Includes tools to develop images using LIDAR point Includes tools to develop images using LIDAR point

cloud (colored by elevation or intensity)cloud (colored by elevation or intensity) LDV – 3D data visualizationLDV – 3D data visualization

Very interactiveVery interactive Provides a variety of display optionsProvides a variety of display options Allows direct measurement in dataAllows direct measurement in data Provides structured measurement protocol for Provides structured measurement protocol for

measuring tree attributesmeasuring tree attributes Provides analysis framework for prototyping analysis Provides analysis framework for prototyping analysis

strategiesstrategies


ConclusionsConclusions

LIDAR can help foresters characterize LIDAR can help foresters characterize spatial variability in forest conditions at spatial variability in forest conditions at resolutions beyond our wildest dreamsresolutions beyond our wildest dreams

Cost is decreasing while LIDAR system Cost is decreasing while LIDAR system capabilities are increasingcapabilities are increasing

Analysis procedures are being defined Analysis procedures are being defined and refinedand refined


ConclusionsConclusions

The number of commercial LIDAR providers is The number of commercial LIDAR providers is increasingincreasing

More competition, more work, more interest in uses More competition, more work, more interest in uses other than bare-earth modelingother than bare-earth modeling

Large LIDAR acquisitions are underwayLarge LIDAR acquisitions are underway Foresters and other resource specialists need to be “at Foresters and other resource specialists need to be “at

the table” when decisions regarding data specifications the table” when decisions regarding data specifications are madeare made

Raw return data is always valuable even if the analysis Raw return data is always valuable even if the analysis tools and methods are not fully maturetools and methods are not fully mature

FUSION will be demonstrated ThursdayFUSION will be demonstrated Thursday

Considerations for Planning, Acquiring, and Processing LIDAR Data for Forestry Applications University of Washington-Precision Forestry Cooperative Pacific.

Documents

pulse multiple returns

forest models team robert

laser systems

remaining laser energy

laser beam

aircraft slide

nm slide

mcgaughey usda forest