Transcript ASPRS_part5 - Berry and Associates Spatial Information Systems

Grid-based Map Analysis Techniques and
Modeling Workshop
Part 1 – Maps as Data
Part 2– Surface Modeling
Part 3 – Spatial Data Mining
Part 4 – Spatial Analysis
Part 5 – GIS Modeling
Modeling structure
Processing hierarchy and analysis levels
Calibrating and weighting model criteria
Simulating alternative scenarios and perspectives
Campground Suitability Model (Demo)
…evaluate a GIS model for Campground Suitability
with the following criteria—
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Prefer gentle slopes
Prefer near roads
Prefer near water
Prefer good views of water
Prefer westerly aspect
…can’t be too close to water or too steep (legal constraints)
(Berry)
Communicating Model Logic (suitability)
(Berry)
Decision Support Systems Framework
An Interactive Map links a map’s logic
(flowchart) to its processing script
(commands) and base data. A user can
query the logic (click on boxes and
maps) and modify calibrations/weights
for alternate scenarios—
What if
…thinking with maps
(See MapCalc Applications, “Identifying Campground Suitability” for more information)
(Berry)
Transmission Line Routing Model
Existing Powerline
Goal – identify the best route for an electric
transmission line that considers various criteria
for minimizing adverse impacts.
Proposed
Substation
Houses
Criteria – the transmission line route should…
 Avoid areas of high
Roads
housing density
Sensitive Areas
 Avoid areas that are far from
roads
Elevation
 Avoid areas within
or near sensitive areas
 Avoid areas of high visual
exposure to houses
Houses
(Berry)
Routing Model Flowchart (Model Logic—components)
Model logic is captured in a flowchart where the boxes represent
maps and lines identify processing steps leading to a spatial solution
Avoid areas of…
High Housing
Density
Far from Roads
In or Near
Sensitive Areas
High Visual
Exposure
(Berry)
Routing Model Flowchart (Model Logic—maps)
Model logic is captured in a flowchart where the boxes represent
maps and lines identify processing steps leading to a spatial solution
Step 1
Identify overall
Discrete Preference
(1-9 rating)
Step 2
Generate an
Accumulated
Preference surface
from the starting
location to
everywhere
Step 3
Step 2
Step 1
Step 3
Identify the Most
Preferred Route
from the end
location
(Berry)
Step 1
Discrete Preference Map
… identifies the relative preference of locating a
transmission line at any location throughout a project
area considering multiple criteria
AVOID
Least
Preferred
Most
ATTRACT
EXCLUDE (0)
…average of the four
individual preference
maps for overall
preference at each cell
(Berry)
Step 2
Accumulated Preference Map
… identifies the preference to construct the
preferred transmission line from a starting
location to everywhere in a project area
Splash Algorithm – like tossing a stick into a pond with waves
emanating out and accumulating costs as the wave front moves
(Berry)
Step 3
Most Preferred Route
… the steepest downhill path over the
accumulated preference surface identifies the
most preferred route — minimizes areas to avoid
Preferred Route
Preferred
Route
(Berry)
Generating Optimal Path Corridors
…technique combines
the Start and End
preference surfaces to
identify the overall
preference for
“forcing” routes off
the optimal path
Pinch Point
The alternative
corridors are
derived by
considering the
top 5 percent of
the best routes
within the
project area
(Berry)
Siting Model Flowchart (Calibrating and Weighting)
Model logic is captured in a flowchart where the boxes represent
maps and lines identify processing steps leading to a spatial solution
Rankings
Weights
Avoid areas of…
High Housing
Density
Far from Roads
In or Near
Sensitive Areas
High Visual
Exposure
…but what is high
housing density and
how important is it?
…etc?
(Berry)
Calibrating Map Layers (Relative Preferences)
Model calibration refers to establishing a consistent scale from 1
(most preferred) to 9 (least preferred) for rating each map layer
1 for 0 to 5 houses
…group consensus is that
low housing density is
most preferred
The Delphi Process
is used to achieve
consensus among
group participants.
It is a structured
method involving
iterative use of
anonymous
questionnaires and
controlled feedback
with statistical
aggregation of
group response.
(See www.innovativegis.com/basis, select Column Supplements, Beyond Mapping, September 03, Delphi)
(Berry)
Weighting Map Layers (Relative Importance)
Model weighting establishes the relative importance among map
layers (model criteria) on a multiplicative scale
…group consensus is that housing density is very important (10.38 times more important than sensitive areas)
HD * 10.38
R * 3.23
SA * 1.00
VE * 10.64
The Analytical Hierarchy Process (AHP) establishes relative importance among by
mathematically summarizing paired comparisons of map layers’ importance.
(See www.innovativegis.com/basis, select Column Supplements, Beyond Mapping, September 03, AHP)
(Berry)
Generating Alternate Routes (changing weights)
The model is run using three
different sets of weights for the
map layers—
…to generate three alternative
routes (draped over Elevation)
(Berry)
Grid-based Map Analysis Techniques and
Modeling Workshop
Part 1 – Maps as Data
Part 2– Surface Modeling
Part 3 – Spatial Data Mining
Part 4 – Spatial Analysis
Part 5 – GIS Modeling
More on Spatial Analysis and Modeling
www.innovativegis.com/basis
Online
Books
Software
(Berry)