2016 foss4 g track: grass gis point cloud exploratory data analysis an open source toolkit for...
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GRASS GIS Point Cloud Exploratory Data AnalysisAn Open Source toolkit for point cloud data processing
September, 2016
Robert S. [email protected]
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grass.osgeo.org
A reliable and flexible open source analytical geospatial processing engine
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grassmac.wikidot.com
Introduction
• Exploratory Analysis?
• What/Why GRASS?
• GRASS with point cloud?
• Examples
• Future?
• Take aways
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Exploratory Analysis
• Point Cloud
• Vast amounts of data
• Millions / Billions of Points
• Challenges
• Visualize
• Validate
• Analyze
• Rapid
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Processing Workflow Overview
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Map Display
2D / 3D
View
Integrate
Bash / Python
Script
#!
r.out.gdal
v.out.ogr
Export
r.* - Raster
v.* - Vector
i.* - Imagery
g.* - General
db.* - Database
t.* - Time
Analyze
r.in.lidar
v,in.lidar
Import
GRASS GIS - Point Cloud Data Import
$ r.in.lidar -e -o --overwrite input=<required> \ output=<required> method=min zrange=5000,6000 \ resolution=2.0 return_filter=last class_filter=2
-e = extend computational region based on dataset
-o = override dataset project - use grass database
-- overwrite = overwrite dataset - often needed in exploratory mode
method = choose statistic (min, mean, max…etc) for raster import binning
zrange = only import points between 5000 and 6000
return_filter = filters by first, middle, last return
class_filter = filters by classification (2 = ground)
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Format: ASPRS - LAS*
Computational Region
• Raster processing significant & powerful
• Vector processsing not as important
• except when deriving vectors from raster
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Interstate 25, Albuquerque, NM
Mobile LiDAR Visualization
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G
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SIG
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I-25, Albuquerque, NM211.8 million pointssize 7.2 GB3 miles
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grass terminal window
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r.in.lidar graphical user interface (gui)
Interstate 25 Intensity Image
Moblie LiDAR (0.3 ft GSD)
0 100
feet
Assessment
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Interstate 25 Intensity Image
Moblie LiDAR (0.3 ft GSD)
0 100
feet
Assessment
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Interstate 25 Intensity Image
Moblie LiDAR (0.3 ft GSD)
0 100
feet
Interstate 25 Intensity Image
Moblie LiDAR (0.3 ft GSD)
0 100
feet
Assessment
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Interstate 25 Intensity Image
Moblie LiDAR (0.3 ft GSD)
0 100
feet
Interstate 25 Intensity Image
Moblie LiDAR (0.3 ft GSD)
0 100
feet
Assessment
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Calabacillas Arroyo, Albuquerque, NM
Change Detection
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G
R
A
S
SIG
LiDAR 20101.4 m NPS182 MB
Photogrammetry 20145M Points 37M Points6-inch GSD
1.27 GBprocessing time: 52
seconds
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highlights: r.in.lidar x 2
•r.in.lidar• dsm
• dsm
•r.mapcalc
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r.mapcalc
r.mapcalc --overwrite expression="SGM_minus_LiDAR = SGM_2014_CAB - LiDAR_2010_CAB"
2014 2010 difference- =
Extract change areas (raster & vector)differences between ±1 & ±10 feet
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Santa Fe, NM
Data Validation
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G
R
A
S
SIG
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strip 101 flight line109.4 million points
size 3.78 GB7 minutes and 31 seconds
strip 100 flight line102.1 million pointssize 3.54 GB
Visualize / Analyze - ~37 mi. by 0.45 mi. point clouds
Santa Fe County, NM
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strip 101 flight line109.4 million points
size 3.78 GB7 minutes and 31 seconds
strip 100 flight line102.1 million pointssize 3.54 GB
Visualize / Analyze - ~37 mi. by 0.45 mi. point clouds
Santa Fe County, NM
Spatial Distribution and Regularity
• density grid =
• 2 X design ANPS =
• 2 * 0.71 = 1.42 m
• 90 percent of the cells in the grid =
• 1 point
• Using individual (single) swaths,
• only the first return points
• located within the center part
• Excluding acceptable data voids
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highlights: r.in.lidar x 3
•r.in.lidar•intensity
•dsm
•count
•r.stats•ps.map
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Strip 101 Point Per Cell Map4.66 ft GSD
0 0.5
miles
Strip 101 Intensity Image4.66 ft GSD
0 0.5
miles
Strip 101 Color Relief MapElevation in feet
0 0.5
miles
-i intensity method=min
r.in.lidar
count
return=first
• number of points in cell
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count
• Strip 100 = 0.10% = zero
• Strip 101 = 0.08% = zero
r.stats -acpl in=$map4 sort=asc sep=comma output=- > output/$map21
cat output/$map21 | grep ^0, >> output/zero_count.csv
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output - visualization
ps.map --overwrite input=output/$map22 output=output/$map23ps2pdfwr -dPDFSETTINGS=/prepress -r1200 output/$map23
Strip 100 Strip 101
Strip_100_intensity_466ft Strip_101_intensity_466ft
Rio Grande, NM
1960s - River Centerline
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R
A
S
SIG
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LiDAR 2014Santa Fe County
strip 101 flight line swaths109.4 million points
size 3.78 GB7 minutes and 55 seconds
LiDAR 2014Santa Fe Countystrip 100 flight line swaths102.1 million pointssize 3.54 GB4 minutes and 2 seconds
Bureau of Reclamation 1962 Photos83.2 million pointssize 2.16 GB12 hours, 52 minutes and 55 seconds11 square miles11 river miles
Rio Grande Bosque Farms, NM
highlights: r.in.lidar x 2
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• r.in.lidar• intensity (ortho)
• dsm
• i.segment• obia
• r.slope.aspect• r.roughness.vector
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1962 Digital Surface Model (DSM)
Color Shaded Relief (elevation in meters)
0 1
kilometers
1962 Photography − U.S. Bureau of Reclamation
Point Cloud Orthophoto (0.6 m GSD)
0 1
kilometers
r.in.lidar
-i intensity dsm
1960s vintage QL2 surface
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0.51962 Object Based Image Analysis (OBIA)
threshold=0.5 (i.segment) random colors
0 1
kilometers
0.31962 Object Based Image Analysis (OBIA)
threshold=0.3 (i.segment) random colors
0 1
kilometers
0.21962 Object Based Image Analysis (OBIA)
threshold=0.2 (i.segment) random colors
0 1
kilometers
0.051962 Object Based Image Analysis (OBIA)
threshold=0.05 (i.segment) random colors
0 1
kilometers
0.11962 Object Based Image Analysis (OBIA)
threshold=0.1 (i.segment) random colors
0 1
kilometers
0.021962 Object Based Image Analysis (OBIA)
threshold=0.02 (i.segment) random colors
0 1
kilometers
i.segment
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1962 Aspect Map
Point cloud derived aspect (in degrees)
0 1
kilometers
1962 Slope Map
Point cloud derived slope (in degrees)
0 1
kilometers
r.slope.aspect
slope aspect
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1962 Topographic Dispersion Map
Surface roughness Fisher’s K parameter (r.roughness.vector)
0 1
kilometers
1962 Topographic Strength Map
Surface roughness vector strength (r.roughness.vector)
0 1
kilometers
strength fisher’s k
g.extensionr.roughness.vector
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1962 Topographic Dispersion Map
Surface roughness Fisher’s K parameter (r.roughness.vector)
0 1
kilometers
1962 Topographic Strength Map
Surface roughness vector strength (r.roughness.vector)
0 1
kilometers
strength fisher’s k
g.extensionr.roughness.vector
Grohmann, C.H., Smith, M.J. & Riccomini, C., 2011. Multiscale Analysis of Topographic Surface Roughness in
the Midland Valley, Scotland. Geoscience and Remote Sensing, IEEE Transactions on, 49:1200-1213. http://
dx.doi.org/10.1109/TGRS.2010.2053546
Boca Negra Arroyo, Albuquerque, NM
Drainage Basin Study
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SIG
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LiDAR 2014Santa Fe County
strip 101 flight line swaths109.4 million points
size 3.78 GB7 minutes and 55 seconds
LiDAR 2014Santa Fe Countystrip 100 flight line swaths102.1 million pointssize 3.54 GB4 minutes and 2 seconds
Mid-Region Council of Governments 2010 LiDAR187.6 million points (1.4 m NPS)
size 6.38 GB7 minutes and 4 seconds
Boca Negra Arroyo, Albuquerque, NM
highlights: r.in.lidar x 1
• r.in.lidar• dsm
• r.watershed• accumulation
• direction
• basin
• flow path
• v.generalize
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DSM
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Elevation: MRCOG2010 (feet) 0 5
miles
Flow Accumulation
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Flow Accumulation0 5
miles
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Basin Boundary
v.generalize input=$map8 output=$map10 method=chaiken threshold=6 --overwrite
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Basin Boundary
v.generalize input=$map8 output=$map10 method=chaiken threshold=6 --overwrite
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Basin Boundary - 16.3 sq. miles
Lubbock, TX
DSM Development - Targeted Building Collection
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G
R
A
S
SIG
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LiDAR 2014Santa Fe County
strip 101 flight line swaths109.4 million points
size 3.78 GB7 minutes and 55 seconds
LiDAR 2014Santa Fe Countystrip 100 flight line swaths102.1 million pointssize 3.54 GB4 minutes and 2 seconds
2016 Photogrammetric Semi-global Matching Point clouds1 file: 141 million points (3-inch GSD)
size 4.82 GB3763 total files - 502 square miles
4 hours and 18 minutes
Lubbock, TX
highlights: r.in.lidar x 1
• r.in.lidar• dsm
• r.to.vect• polygon outline
v.hull• generalize
v.buffer• interior clip
• r.out.gdal• output GeoTiff
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2016 Lubbock Digital Surface ModelSemi−global matching photogrammetric point clouds (3763)
0 10
miles
Point Cloud DSM
• Decimated Point
Cloud
• 141 M -> 4 M (2%)
• 4.6 GB -> 140 MB
• r.in.lidar
• 3.0 ft GSD
• 4 hours processing
• 6 core machine
• 10 simultaneous
GRASS databases
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2016 Lubbock DSMColor Relief Map (elevation in feet)
0 0.5
miles
2015 Lubbock DSMColor Relief Map (elevation in feet)
0 0.5
miles
r.in.lidar
2015 leaf-off 2016 leaf-on
2016 Lubbock Normalized Difference Vegetation Index (NDVI)
DSM / NDVI Candidate Building Detection
Buildings
Candidate Building 0 0.25 44
New Candidate Buildings
2016 NDVI
• GRASS Development Team, 2015. Geographic Resources
Analysis Support System (GRASS) Software, Version 7.0. Open
Source Geospatial Foundation. http://grass.osgeo.org
• Michael Barton, PhD. - GRASS Macintosh Binaries http://
grassmac.wikidot.com/
Acknowledgements
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