Transcript Panel Discussion What’s Next? The Way Forward

Incorporating Grid-based
Terrain Modeling
into Linear Infrastructure
Analysis
Joseph K. Berry and Nate Mattie
W.M. Keck Scholar in Geosciences, University of Denver
Principal, Berry & Associates /// Spatial Information Systems
Senior Consultant , New Century Software
Desktop Mapping Framework (Vector)
Click on…
Select Theme
Zoom Pan
Info
Tool
Theme
Table
Now for a
Geo-Query…
Distance
Spatial
Table
:
Object ID
X,Y
X,Y
X,Y
:
Query
Builder
…identify tall
aspen stands
Attribute
Table
Feature
:
Object ID
:
Species
:
Aw
:
Big …over 400,000m2 (40ha)?
Discrete, irregular map features (objects)
etc.
MAP Analysis Framework (Raster)
Click on…
Zoom Pan Rotate
Display
Shading
Manager
Grid
Analysis
…calculate a
slope map and
drape on the
elevation surface
Grid
Table
:
--, --, --, --,
--, --, --, --,
--, --, --, --,
--, 2438, --,
--, --, --, --,
:
Slope map
Slope map draped
on Elevation surface
Continuous, regular grid cells (objects)
Points, Lines, Polygons and Surfaces
Calculating Slope and Flow (map analysis)
Inclination of a fitted
plane to a location and
its eight surrounding
elevation values
Slope (47,64) = 33.23%
Slope map draped
on Elevation
Slope map
Elevation Surface
Flow (28,46) = 451 Paths
Total number of the steepest
downhill paths flowing into each
location
Flow map draped
on Elevation
Flow map
Deriving Erosion Potential
Erosion Potential
Slopemap
Slope_classes
Flowmap
Flow_classes
But all buffer-feet are not the same…
Need to reach farther under some conditions
and not as far under others— common sense?
Simple Buffer
Flow/Slope
Erosion_potential
Calculating Effective Distance (variable-width buffers)
Distance away from the streams is a
function of the erosion potential (Flow/Slope
Class) with intervening heavy flow and steep
slopes computed as effectively closer than
simple distance— “as the crow walks”
Erosion_potential
Erosion Buffers
Streams
Effective Erosion Distance
Close
Far
Simple Buffer
Heavy/Steep
(far from stream)
Light/Gentle
(close)
Effective Buffers
Down/Uphill Proximity (Terrain Analysis)
End
Pipeline
Down/Uphill movement can
be identified from a set of
points, lines or areas—
a “downhill” buffer
Start
Downhill from Pipeline
Drain Paths
Far
Close
Visual Exposure (Terrain Analysis)
End
Pipeline
Line-of-sight connectivity
from the pipeline to all
other locations—
a “scattered” buffer
Start
High Visual Exposure
High
Low
Basic and Advanced Distance Operations
Basic Operations—
 Simple Proximity as the crow flies (straight lines)
 Weighted Proximity recognizes differences in mover characteristics
 Effective Proximity as the crow walks (not necessarily straight respecting
absolute and relative barriers)
…imply movement
Advanced Operations—
 Guiding Surface restricted movement (Up/Downhill)
 Directional Effects (bearing; up/across slope)
 Accumulation Effects (wear and tear)
 Momentum Effects (acceleration/deceleration with movement)
 Stepped Movement (go until specified location then restart)
 Back Azimuth (direction of travel)
 1st and 2nd Derivative (speed and change in speed)
Mapped Data Analysis Evolution (Revolution)
Traditional GIS
Spatial Analysis
Erosion Potential
(Surface)
Forest
Inventory Map
• Points, Lines, Polygons
• Cells, Surfaces
• Discrete Objects
• Continuous Geographic Space
• Mapping and Geo-query
• Contextual Spatial Relationships
Traditional Statistics
Spatial Statistics
Spatial
Distribution
(Surface)
Minimum= 5.4 ppm
Maximum= 103.0 ppm
Mean= 22.4 ppm
StDEV= 15.5
• Mean, StDev (Normal Curve)
• Map of Variance (gradient)
• Central Tendency
• Spatial Distribution
• Typical Response (scalar)
• Numerical Spatial Relationships
Longitudinal and Traverse Slope (Terrain Analysis)
2
1
3
Longitudinal Slope (LS) – steepness of the terrain in the
direction of the pipeline. In the example, the average of the
individual slopes for positions 5-3 and 5-7 is reported.
Traverse Slope (TS) – steepness of the terrain
4
5
perpendicular to the direction of the pipeline. In the
example, the average of the individual slopes for positions
5-1 and 5-9 is reported.
6
7
8
9
1
2
3
…but how is “perpendicular” defined for nonsymmetrical grid representations of line
patterns?
Modified Traverse Slope (MTS) – steepness of the
4
5
terrain off the pipeline. In the example, the average of the
six individual slopes for positions 5-1, 5-2, 5-6, 5-9,5-8 and
5-4 is reported.
6
LS = avg (5-6,5-7)
MTS = avg (5-1,5-2, 5-3, 5-4, 5-9,5-8)
7
8
9
Analyzing Terrain Inflections (Terrain Analysis)
Smoothed
Elevation
Convex Feature
(above smoothed Elevation
Elevation
Actual
Elevation
Concave Feature
(below)
Smoothed
Elevation
- Smoothed
Difference
Terrain Inflection
Over Elevation
Terrain-based Segmentation (Terrain Analysis)
:
114-121= -7
121-127= -6
127-124= +3
124-118= +6
:
…sign change indicates
an inflection point
End
#7
Pipeline
#6
#5
114
121 127 124 118
#4
105
#3
#2
#1
Actual Elevation
Start
Smoothed
Segment #1
Proposed Route Profile
#6
#7
Segment #1
#5
#2
Start
#3
#4
End
Actual Elevation
Smoothed
Overland Flow Modeling (Spill Migration Modeling)
Elevation
Surface
Overland Flow Model
1)
2)
X
Spill Point #1
X
Pipeline
5) Flowing
Water
3)
HCA
4)
Report
HCA Impact
The Pipeline is positioned on the Elevation surface
2) Flow from Spill Points along the pipeline are simulated
3) High Consequence Areas (HCA) are identified
4) A Report is written identifying flow paths that cross HCA areas
5) Overland flow is halted when Water is encountered (Channel Flow Model)
1)
Flow Paths
Surface flow takes the steepest downhill path whenever possible
Types of Surface Flows
Common sense suggests that “water flows downhill”
however the corollary is “…but not always the same way”
Path Flow
Sheet Flow
Flat Flow
…function of steepness and
product type
Pooling – accumulation until
depression is filled and path
moves on from exit location
(lowest surrounding location)
Characterizing Overland Flow and Quantity
Intervening terrain and conditions form Flow Impedance and Quantity
maps that are used to estimate flow time and retention
Simulating Different Product Types
Physical properties combine with terrain/conditions to model
the flow of different product types
Flow Velocity is a function of—
Specific Gravity (p), Viscosity (n) and Depth (h) of product
Slope Angle (spatial variable computed for each grid cell)
Characterizing Impacted Areas
The minimum time for flows from
all spills… characterizes the impact
for the High Consequence Areas
Flows from spill 1, 2 and 3
Drinking
Water HCA
Drinking water HCA
Impacted portion of the Drinking water HCA
Channel Flow Characteristics
HCA Impact
3)
Impacted
HCA Times
HCA
4)
Out= 9.86 hr
Report characterizing
Impacted HCA’s
Base
Point
0 hr
In= 11.46 hr
HCA
HCA
X = 12.10 + .36 = 12.46 hr
HCA
HCA
away from Base Point
2)
13.1 hr
.27
8.4 hr
.25
13.1 hr
.14
1)
7.3 hr
11.2 hr
11.2 hr
X
.72
X
.12
.12
.78
13.6 hr
Overland Flow
Entry Time
Overland Flow
(2.5 hours)
6.2 hr
Channel Flow Time
HCA
Channel Flow
9.6 hr
Model
10.1 hr
10.8 hr
Channel Flow along stream network segments is added
2) Overland Flow time and quantity at entry is noted
3) Impacted High Consequence Areas (HCA) are identified
4) A Report is written identifying flow paths that cross HCA areas
1)
Overland and Channel Flow Results
Overland Flow
Channel Flow
HCA Intersect Table
Conclusions
 While the computations of terrain analysis might appear
complex, once coded they are easily and quickly performed by
modern computers.
 In addition, there is a rapidly growing wealth of digital data
that describe conditions determining how infrastructure is
connected in the real world.
 The experience base of potential users is the major
impediment for use of these new ways of relating features to
their surroundings.
 While comfortable, simply automating traditional manual
procedures fails to address the reality of complex spatial
problems or fully engage the potential of GIS technology.
 Grid-based terrain analysis is but one of numerous paradigm
shifts encountered when moving traditional beyond mapping
toward map analysis.
References
ONLINE REFERENCES
See the online book Map Analysis by Joseph K. Berry
(BASIS Press) that is posted at
www.innovativegis.com/basis
Select the following topics for more information on gridbased map analysis and procedures for analyzing terrain
conditions and flows (listed in order of discussion this
paper):
 Topic 18, Understanding Grid-based Data
 Topic 11, Characterizing Micro Terrain Features
 Topic 20, Surface Flow Modeling
 Topic 19, Routing and Optimal Paths
Joseph K. Berry, [email protected]