hydro-enhancement of lidar data to support floodplain modeling 2011 asfpm annual conference...
TRANSCRIPT
Hydro-enhancement of LiDAR Data to Support Floodplain Modeling
2011 ASFPM Annual ConferenceLouisville, Kentucky
May 18, 2011
Mark W. Ellard, PE, CFMAssociate, Water Resources
Edward C. Beute, PSM, CPVice President LiDAR Operations
Presentation Outline
Role of LiDAR in Watershed Modeling
Hydrological Representation of LiDAR
Issues with LiDAR & Modeling
LiDAR Data Collection & Classification Overview
LiDAR Hydro-enhancement
Modeling Results Impact
• Detailed Surface Representation
• Digital Data Source
• Easy to Update Incrementally (i.e., New Development, etc.)
• Easy to Take for Granted
Role of LiDAR in Watershed Modeling
Role of LiDAR in Watershed Modeling
Inundation
Calibration & Verification
Surface Storage & ConveyanceRepresentation
Hydrological Response – Rainfall Excess Estimation
Detailed Topographical Representation
Flood Model Foundation
• GIS Processing for Model Parameterization
– Catchment / Basin Delineation
– Storage Extraction
– Cross-section Extraction
– Flow Path Tracking
– Floodplain Inundation
Hydrological Representation of LiDAR
• Conditions in Florida that Cause Problems– Non-Dendritic Watersheds– Flat Topography– Thick Vegetation Obscures Ground Surface
• Misrepresentation of Storage– Lakes / Ponds – Initial Stages– Sloped Water Surfaces (rivers, canals, etc.)– Affects Estimates of Floodplain Depth
• Misrepresentation of Conveyance– Channels– Overland Flow– Inaccuracies in Floodplain Depth and Flow
Issues with LiDAR & Modeling
Issues with LiDAR & Modeling
Issues with LiDAR & Modeling
Issues with LiDAR & Modeling
Issues with LiDAR & ModelingSurvey Enhancement of Conveyance Features
(Ditches, Canals, etc.)
• Laser scanner, Survey Grade GPS Receivers, Inertial Measurement Unit (IMU), Aircraft
• Processing Computers, Proprietary Software• Collection is project specific which determines
altitude, ground speed, pulse rate repetition, and point density.
• Every project must have a boresite calibration flight
LiDAR Data Collection & Classification Overview
LiDAR Collection Process
LiDAR Data Collection & Classification Overview
• Data extraction• Processing of trajectory for position and orientation
of the sensor• Pre-processing data using proprietary software• Output data in LAS format in project specific
coordinates and units
LiDAR Data Collection & Classification Overview
LiDAR Processing
• Off The Shelf (TerraScan) or proprietary software• Automated Routines using a set of parameters
designed to model the bare earth ground and other useful information
• Terrain specific parameters• Allows for batch processing of a project
LiDAR Data Collection & Classification Overview
Classification Process
• Automated routines will correctly model most of the project
• Some conditions do not meet the criteria set up in the automated routines
• Labor intensive manual classification is necessary for the remainder
• It is labor intensive is necessary where conditions for automated routines are not met
LiDAR Data Collection & Classification Overview
Classification Process
Some common errors:Over filtering the data• data is smoothed showing no artifacts• valuable ground information is missing
Under filtering the data• data is noisy due to artifacts • Non-ground added to the ground
Modeling is compromised in both scenarios
LiDAR Data Collection & Classification Overview
Classification Process
LiDAR Hydro-enhancement
Original Data Enhanced Data
LiDAR Hydro-enhancement
LiDAR Hydro-enhancement Classifications as Delivered
Orange = Bare Earth
LiDAR Hydro-enhancement Classifications after Hydro-enhancement
Orange = Bare Earth
LiDAR Hydro-enhancement Classifications as Delivered
Orange = Bare Earth
LiDAR Hydro-enhancement Classifications after Hydro-enhancement
Orange = Bare Earth
LiDAR Hydro-enhancement
Classifications as Delivered Classifications after Hydro-enhancement
LiDAR Hydro-enhancement
Classifications as Delivered Classifications after Hydro-enhancement
LiDAR Hydro-enhancement
Classifications as Delivered Classifications after Hydro-enhancement
LiDAR Hydro-enhancement
• Examine the data for suitability by identifying holidays, voids, and point density
• Consider enhancement of data through reclassification to obtain additional ground points, identify structures and separate vegetation by height
• Supplement or create new 3D break lines using Direct Terrain Extraction techniques (QCoherent LP360, Cardinal Systems VrLiDAR)
LiDAR Hydro-enhancement
Points to Consider
Modeling Results ImpactAerial
Note Dense Vegetation Along
Channel
Modeling Results Impact
Original
Modeling Results Impact
Enhanced
Modeling Results Impact
Original
Modeling Results Impact
Enhanced
• Example Conveyance Feature
Modeling Results Impact
• Example Conveyance Feature
Modeling Results Impact
Modeling Results Impact
• Model Node Stage Impact• Higher Flood Risk Indicated
• 100 Year – 72 Hour Simulation: Time – Stage Plot
OriginalEnhanced
• LiDAR plays an Important Role in Current Floodplain
Modeling Efforts
• Proper Classification of Ground Points is Critical
– Properly Define Conveyance ways
– Properly represent Storage
• Hydro-enhancement Improves Surface Representation
• Better Representation Increases Model Accuracy
Conclusions
Thank You !Mark Ellard, PE, CFM Associate, Water Resources [email protected]
Thomas Amstadt, PE, CFM Professional, Water Resources [email protected]
Edward Beute, PSM, CPVice President LiDAR Operations [email protected]