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LiDAR and GIS:Classification and Feature ExtractionNicholas M. Giner – Esri
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Agenda
• LiDAR basics
• Data formats and management
• The LAS dataset
• Classifying LiDAR
• Feature extraction from LiDAR
- Building footprints / 3D buildings
- Trees
- Traffic lights using machine learning
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LiDAR basics• LiDAR – Light Detection and Ranging
- Optical remote sensing technique using laser light to densely sample the Earth’s surface, producing a point cloud of highly accurate x,y,zmeasurements
• Types of point clouds- Airborne scanned-based LiDAR
- Mobile / Tripod-based LiDAR
- Photogrammetric / Drone-based LiDAR
• LiDAR point cloud attributes- x,y,z measurements
- Intensity
- Return number
- Class code
- RGB
- Overlaps
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Data formats and management• Formats
- LAS / zLAS / LAZ
• Management
LAS Dataset
Mosaic Dataset
Terrain Dataset
Point Cloud Scene Layer
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Demo #1Explore a LAS file, Create a LAS Dataset
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The LAS Dataset• LAS Dataset
- “Container” for storing reference to many LAS/zLAS files on disk
- Pointer to the original LAS/zLAS files
- Quick to create, small in file size, easy to update with additional LAS/zLAS files
- Can reference surface constraints (breaklines / boundaries)
- Quick display of LAS/zLAS data as point clouds or a dynamic TIN in 2D or 3D
- Excellent for QA/QC of LiDAR coverage (point density/spatial extent)
- Basis for generated products such as DEMs and DSMs or TINs
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Working with LiDAR - GeoprocessingData Management (6) 3D Analyst (18) Conversion (2)
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Classifying LiDAR• Automated classification (Geoprocessing)
- Change Class Codes
- Classify Buildings
- Classify Ground
- Classify Noise
- Classify Overlap
- Classify by Height
- Classify by 3D Proximity
- Classify by 2D Proximity (using features)
- Classify using raster
• Interactive classification (Manual)
• Editing considerations
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Workflow: Classifying LiDAR
Unclassified LAS
Classify LASOverlap
Create LASDataset
Classify LASNoise
Classify LASGround
Create DEMClassify LASBuildings
Classify LASby Height (Vegetation)
Colorize LAS
ClassifiedLAS Dataset
Interactivelyedit class codes
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Demo #2Classify LAS data
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Other tools for classification• Change LAS Class Codes
- Reassigns classification codes from one class to another
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Other tools for classification• Classify by 2D and 3D Proximity (vector)
Set LAS Class Codes using Features (2D) Locate LAS Points by Proximity (3D)
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Other tools for classification• Classify using raster
- Requires integer raster with pixel values representing ASPRS LiDAR class codes
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Workflow: Extract building footprints
Classified LAS Dataset
Make LAS Dataset LayerClass Code = 6
LAS Point Statistics as RasterMost Frequent Class
Elevation VoidFill (Optional)
Raster to PolygonNo Simplify
SQL(Remove
small polygons)
EliminatePolygon Part(Fill holes)
Raw buildingpolygons
RegularizeBuildingFootprints
Clean up(Optional)
Building Footprints
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Workflow: Extract traffic lights
Point CNNClassified LAS Dataset
LAS to Multipoint
Explode multipoints
Reduce datasetsize
DBSCANCluster boundariesAdd fields
Remove noisepoints
Calculatefields
Clean up noise polygons
Final outputpoints
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Demo #3Feature extraction: Building footprints, trees, traffic lights
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