# Terrain Analysis Principles and Applications by zbs19295

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```									 High-Resolution Surface
Modeling of River Channels
using Light Detection and
Ranging (LiDAR) Data

Graeme Aggett
Center for Spatial Information @
Central Washington University

RGIS-Pacific NorthWest
aggettg@cwu.edu
Talk Outline
Intro to terrain modeling
Topographic attributes
Channel surface modeling
LiDAR
Developing and testing a LiDAR DEM
Hydraulic Modeling
Resolution Comparison – 1 sq mile
Bainbridge island, WA
Processing LiDAR points and
Developing the LiDAR DEM
Classification and interpolation
Creation of bare earth model
Hydraulic “continuity” and the need for
breaklines
Error assessment
Developing the LiDAR DEM & Terrain Surface

Point_cloud1   Point_cloud2   river fly
Developing the LiDAR DEM & Terrain Surface –
classification
VDF algorithm
ARC-INFO command

Convert TIN to grid1           tinlattice

Calculate 3x3 mean at each     grid2 = focal mean
cell                           (grid1)

Convert TIN vertices to        Tinarc TIN
point database (Z value in     cover1 point
item SPOT)

Calculate item SPOT2 =         latticespot
value of GRID2 at each         grid2 cover1
point in database              spot2

CURVATURE = SPOT2 – SPOT

If CURVATURE > testvalue1
or CURVATURE < testvalue2
then mark point for deletion
What is LiDAR?

CSI
Creation of “bare earth”
terrain model
Fly-thru01
Inputs for Creating a TIN

Mass Points           Soft Breaklines      Hard Breaklines

• Hard breaklines define locations of abrupt surface change
(e.g. stream bank, bridges, dams)
• Soft breaklines are used to ensure that known z values
along a linear feature are maintained in the TIN.
Bank

Sa

L
W

N         Sr
H

θ l
See next slide for nomenclature

Stream Bed
Developing the LiDAR DEM & Terrain
Surface – error assessment
Simple Error budget for LiDAR
points:
GPS used to
extract control
heights at random
locations
RMS error
calculated
Simple Error budget for LiDAR DEM:

Z error = [ (measurement error)2 +
(classification error)2 + (interpolation
error)2 ]1/2
Naches 2 points 1501-1639 {5z}
River   Mid-channel Bar   River
Comparison plotting
Profile 01

840

820

800
Elevation (Feet)

LIDAR
780                                                           Photo

760
USGS

740

720
0.00    5000.00   10000.00           15000.00   20000.00
Distance (feet)