Geospatial analysis and modeling with open source GIS: education and research

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Geospatial analysis and modeling with open source
GISeducation and research

• Helena Mitasova
• North Carolina State University

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Outline
NCSU GIST program and open source GIS Modeling
and analysis course examples 3D
visualization cost surfaces and shortest
path terrain modeling - topobathy terrain
analysis - lidar data time series viewshed,
solar flow tracing, hydro, erosion tangis
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NCSU GIS curriculum
MS in GIST, non thesis DE certificate minor updat
ed set of courses modeling and analysis, open
source GIS, python programming Updated NCSU GIS
curriculum now includes Open Source GRASS GIS
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Teaching with GRASS6

• Geospatial Modeling and Analysis course is
  designed with assignments in GRASS GIS and
  ArcGIS
• Data integration, display and 3D visualization
• Proximity analysis, cost surfaces
• Terrain modeling, analysis, geomorphometry
• Flow tracing, watershed analysis, landforms
• Modeling geospatial processes, Tangible GIS

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Cumulative cost surfaces

• find the fire station from which the help can
  come the fastest and find the least cost path

Deriving a cost map from speed limit
Cumulative cost surface
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Cost surface from friction map

• Map showing the time it will take walking person
  to get to each cell. Orange isochrone delineates
  search area for given time

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Terrain modeling

• Multiple return point cloud data from 2001 NC
  Flood mapping program yellow is first return

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Increasing LIDAR point density
no. of points/2m grid cell 1996 0.2 1997
0.9 1998 0.4 1999 1.4 2001 0.2 NCflood 2003
2.0 2004 15.0 2005 6.0 2007 5.0? 2008 5.0?
substantially improved representation of
structures but much larger data sets
2004 lidar, 0.5m resolution DEM binned and
computed by RST (smoothes out the noise and
fills in the gaps)
1m res. DEM, computed by RST, 1998 lidar data
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USACE SHOALS LIDAR topo mapping
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Data SourcesBeach ProfilesWrightsville Beach,
Topsail, Topsail Island, Pea Island, Ocean
Isle-Shallotte-Holden Beach, Oak Island-Bald
Head, FRF Duck, Fort Fisher, Figure 8 Island,
Dare County, Carolina Kure, Bear Island,
Bogue-Shackleford BanksInletsTopsail,
Shallotte, Rich-Nixon Green Channel, Oregon, New
River, Mason, Masonboro, Lockwoods Folly, Cape
Fear, Bogue, Beaufort, BardenNational Ocean
Service soundings

• North Carolina Floodplain Mapping Project

Lisa Stillwell, RENCI
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CRM and profile data

• North Carolina Floodplain Mapping Project

Longshore profiles improve accuracy of
interpolated DEMs (Mitasova, Bernstein
papers)New method for data thinning should
preserve more detail
Cape Fear
Mason
New River
Topsail
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Topobathy 2.3 and 2008 lidar
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Digital Elevation Modelrelease 2.3

• North Carolina Floodplain Mapping Project

• 10 meter resolution
• 54,000 x 54,000 cells
• 2,916,000,000 total cells

http//tornado.renci.org/renci_ncfmp/
Lisa Stillwell, RENCI
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Workflow topographic change

• Data integration coordinate system
  transformation
• Point density and noise analysis selection of
  common resolution and gridding method using
  binning (per cell statistics) no. of points per
  cell, z-range within cell, mean z
• Simultaneous spatial approximation (gridding),
  smoothing of random noise and computation of
  topographic parameters using splines
• Detection of systematic error and its
  elimination for all DEMs using roads and NCDOT
  benchmarks, evaluation of interpolation accuracy
• Result is time series of corrected, smoothed,
  high resolution DEMs

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Workflow topographic change

• Two approaches
• measuring migration and change of features, such
  as shorelines, ridges, crests, peaks (Jockeys
  Ridge)
• raster-based time series analysis per cell
  statistics where each grid cell in the resulting
  map is function of grid cells in the entire time
  series in the same location

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Spatial coastal change indicators

• New, spatial indicators representing coastal
  terrain evolution based on per grid cell
  statistics using r.series
• core surface below which elevation never
  decreased
• outer envelope above which elevation never
  increased (core is 67 the envelope volume)?
• standard deviation map shows areas with most
  elevation change in red
• Mitasova, Overton, Recalde, Bernstein, Freeman,
  2009, JCR 25(2)
• Wegmann and Clements, 2004, GRASS Newsletter

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Spatial and temporal indicators
a) time at minimum and b) time at maximum
maps represent timeyear when the grid cell was
at its minimum and its maximum elevation c)
regression slope maps show spatial pattern of
elevation trends, inset transparency added as
function of correlation coefficient, white areas
have r2lt0.3
increase decrease
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Spatial and temporal indicators
regression slope maps show spatial pattern of
elevation trends, inset transparency added as
function of correlation coefficient, white areas
have r2lt0.3
increase decrease
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Coastal change indicators structures
Beach and dunes near Oregon Inlet

• In areas with homes core surface and outer
  envelope can be used to map new and old homes and
  their relation to core
• Some new homes built with exception from
  regulations do not have any core surface
• Derived from 2m res. DEMs 1996-2008

Beach and homes in Rodanthe
0 100m
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Coastal change indicators structures
Beach and homes in Rodanthe

• core surface
• outer envelope
• 0m elevation
• derived from 0.5m resolution DEMs

0 100m
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Shoreline dynamics band
0 m contours outer envelope core surface 2008
surface (white)
0 m contours outer envelope core surface 2008
surface (white)
accretion erosion 2005-2008
1997 - yellow 1998 - orange 1999 - red 2001 -
magenta 2003 - violet (june) 2005 - blue 2008 -
white
the distance between the core and outer
envelope surface shorelines ranges between
30-64m (30-90m for the entire study area) and
defines an area within which the shoreline has
been migrating over the years 1997-2008
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Surface evolution as volume
New approach Evolution of terrain surface is
represented as a volume with time used for 3rd
dimension. Evolution of a contour is then
represented as an isosurface. The approach
reveals often neglected high dynamics of
foredunes (zgt 4m) and stability of backshore
beach (z1.5m)?
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GIS and spatial simulations
Explore answers to questions What happens with
water, ecosystems, if - we change land use? -
sea level is 1m higher? - area is flooded or
trees are cut? Create new landscape
configurations in 2D using map algebra or
digitizing If the change is 3D and we need to
explore many scenarios, digitizing becomes
tedious and collaboration is limited
touch systems work in 2D
can we make changes in 3D ?
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Building TanGIS at the VISSTA lab
3D scanners projectors 3D display
workstations web cameras flexible models
System is linked to GIS GRASS, ArcGIS - both
can be used simultaneously Multipurpose facility
at VISSTA Lab at ECE NCSU Prof. Hamid Krim
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3D landscape design with TanGIS
3D laser scanner projector
flexible model with projected orthophoto
Mitasova, H., Mitas, Ratti, Ishii, Alonso,
Harmon, 2006, Real-time Human Interaction With
Landscape Models Using a Tangible Geospatial
Modeling Environment, IEEE CGApp, 26(4).
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3D landscape design with TanGIS
Modify model and scan it
3D laser scanner projector
flexible model with projected orthophoto
Compute DEM, run flow simulation, project the
results (img or animation)?
Mitasova, H., Mitas, Ratti, Ishii, Alonso,
Harmon, 2006, Real-time Human Interaction With
Landscape Models Using a Tangible Geospatial
Modeling Environment, IEEE CGApp, 26(4).
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Case study experimental watershed
Problems sediment deposition, road
flooding Design new land management alternatives
in 3D space and evaluate their impacts
N
1993 photogrammetric DEM
Sediment pollution
N
N
Flooding
0 200m
2001 lidar-based DEM
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Impact of landscape modification
N
initial terrain
flexible clay model
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Impact of landscape modification
initial terrain road breaks

flexible clay model take out piece of
clay
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Impact of landscape modification
initial terrain road breaks
checkdam is added
flexible clay model take out piece of
clay add piece of clay
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Impact of landscape modification
initial terrain road breaks
checkdam is added
flexible clay model take out piece of
clay add piece of clay
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Impact of landscape modification

• Modify landscape
• add buildings, ponds, dams, roads
• change land cover properties
• Compute and project
• elevation or volume change,
• slope and aspect
• viewshed, line of sight
• flow accumulation and watershed boundaries
• soil erosion and deposition,
• solar energy potential

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Terrain with buildings in TanGIS
elevation change
Add buildings
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Terrain with buildings in TanGIS
elevation change
Add buildings
Runoff from buildings, compacted surface
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Terrain with buildings in TanGIS
elevation change
Add buildings
Runoff from buildings only
Runoff from buildings, compacted surface
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Getting creative in TanGIS
Exploring various materials, testing runoff
simulations on surfaces with depressions and
various patterns of roughness
lagoon
porous parking lot
Design by USFWSUSGSNCDENR team
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Getting creative in TanGIS
Exploring various materials, testing runoff
simulations on surfaces with depressions and
various patterns of roughness
lagoon
summer solstice
porous parking lot

• the model does not crash in spite of all the
  pits and flats
• more rainfall is needed to flood the road

Design by USFWSUSGSNCDENR team
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Solar radiation and TanGIS
Where to locate solar pannels? Analyze pattern of
solar radiation
summer solstice 7800-8200 W/m2
winter solstice 0-5700 W/m2
winter solstice
Solar incidence angle at 2pm, building with
cast shadow
cumulative beam solar radiation
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Teaching with GRASS and TanGIS

• Tangible GIS in class
• experiment with laser scanning of different
  materials
• process point clouds of features with different
  geometries and surface properties
• test algorithms for analysis and simulations
• explore and demonstrate spatial impacts of
  landscape change on runoff, erosion, solar
  irradiation, ...

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Open source GIS GRASS6.4 http//grass.osgeo.org
General purpose GIS 2D/3D raster and vector
data management, analysis, modeling,
visualization for Linux, Mac and
MSWindows Developed by US Army CERL
1982-1993 GPL since 1999, current development
coordinated from Trento, Italy, official OSGeo
project GRASS64RC3 available new wxPython GUI,
native MS Windows support, new and enhanced
modules
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Conclusion

Laboratory 3D laser scanning can be used for
Tangible GIS an experimental environment for
analysis of landscape change impacts and
design In our case study simulations show
persistent flooding for wide range of scenarios
except for high infiltration alternative. GRASS
GIS and TanGIS now included in NCSU GIS
curriculum Geospatial Modeling and Analysis
course.
Funding by the US Army Research Office and NC
WRRI is gratefully acknowledged