Transcript Slide 1

CE 250 - Introduction to Surveying
and
Geographic Information
Systems
eLearning Version
Donald J. Leone, Ph.D., P.E.
Lecture 4
Introduction
Data Analysis Operations – turning data

into information
Measurement Techniques
Introduction
Data Analysis Operations – turning data
into information

Measurement Techniques

Attribute Queries
Introduction
Data Analysis Operations – turning data
into information

Measurement Techniques
Attribute Queries

Proximity Analysis

Introduction
Data Analysis Operations – turning data
into information

Measurement Techniques
Attribute Queries
Proximity Analysis

Overlay Operations
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
Introduction
Data Analysis Operations – turning data
into information
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Measurement Techniques
Attribute Queries
Proximity Analysis
Overlay Operations
Analysis of Models of Surfaces and
Networks
Data Analysis Terminology
Term
Definition
Entity
Point, line, polygon
Attribute
Data about an entity
Feature
Object in Real world to be mapped.
Data Layer
Data for an area of common interest.
Image
Data in a raster format
Cell
An individual pixel in a raster image
Function or
Operation
Algorithm
A data analysis procedure performed by
a GIS
A plan composed of a series of steps to
solve a problem.
Measurement Techniques
Measurements
Attribute Queries
Proximity Analysis
Overlay Operations
Analysis of Models of Surfaces
and Networks
Lengths, Perimeters and Areas
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Vector Data
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Raster Data
Vector GIS Measurements
Raster GIS Measurements
C3
1
2
3
4
A3C3 = 5 units
Pythagorean Distance
Manhattan Distance
Perimeter = 26 Units
Area
= 28 Units
Proximity Distance
Measurement Techniques
Attribute Queries
Queries
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Proximity Analysis
Overlay Operations
Analysis of Models of Surfaces
and Networks
Search or Browse the database.
Retrieve data.
Answer questions “How many?”
Answer questions “Where are they?”
Answer questions with more than one
criteria using Boolean Operators.
Boolean Operators
Ski resort Example
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A = Luxury hotels
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B = Hotels with more than 20 rooms
Boolean Operators Continued
Four questions can be answered.
1.Which are hotels are Luxury and have
more than 20 rooms?
2.Which hotels are Luxury or have more that
20 rooms?
3.Which hotels are Luxury but do not have
20 or more bedrooms?
4.Which hotels are either Luxury or have
more that 20 bedrooms, but not both?
Boolean
Operators
A AND B
A OR B
“ Hotels”=‘Luxury’ AND ‘Bedrooms’>20
A NOT B
A XOR B
Venn
Diagrams
Measurement Techniques
Attribute Queries
Queries
Proximity Analysis
Overlay Operations
Analysis of Models of Surfaces
and Networks
Raster Data
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Reclassification.
Can produce a Boolean Image.
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Example: Land Use Raster Image
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Where are all the forested areas?
Bloomfield Land Use
Bloomfield Land Use
Only Forest
Measurement Techniques
Attribute Queries
Proximity Analysis
Overlay Operations
Analysis of Models of Surfaces
and Networks
Proximity Analysis
a.k.a. Buffering
Buffering:
The creation of a zone of interest
around an entity, or set of entities.
Buffer Zones
Point
Line
Area
3 km Buffer Zones Around Railway System
Proximity Map For Hotels in Ski Resort
Distance Surface
125 m Buffer Zones
Measurement Techniques
Attribute Queries
Proximity Analysis
Overlay Operations
Overlay Operations
Analysis of Models of Surfaces
and Networks
Overlay Operations:
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Simply drawing one map or layer
over another.
GIS operation that combines
information from two layers into a
new layer.
Vector Overlay Operations
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Data layers overlayed have to be
topologically correct.
Intersections of lines and polygons from
original layers form new lines and
new polygons in the new layer.
Laws of Geometry and a lot of
computational power needed.
Vector Overlay Types
Point-in polygon
 Line-in-polygon
 Polygon-in-polygon
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Point-in-Polygon
Layer 1
Layer 2
New Layer
New Attribute
Table
Line-in-Polygon
Layer 1
Layer 2
New Layer
New Attribute
Table
1
2
4
3
1
2
1
Layer 1
Layer 2
New Layer
Polygon-in-Polygon
IDENTITY (NOT)
Vector Overlay Rail Buffer Zone and Clay Geology
Little Grey Cells Quiz
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A raster image is made up of cells. T or F
Which Boolean operator will allow both
conditions to exist simultaneously?
The creation of a zone of interest around an
entity, or set of entities is called an overlay.
T or F
Break!
Raster Overlay Operations
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Points, lines, and areas represented by
cells or groups of cells.
Uses map algebra, +, -, x, ÷
Coding or values in the cells needs
to be understood.
Sometimes Boolean images used.
Raster Point-in-Polygon - ADD
Raster Line-in-Polygon - ADD
Raster Polygon-in-Polygon - ADD
Raster Polygon-in-Polygon - +,x
Using Boolean Alternatives
Measurement Techniques
Attribute Queries
Proximity Analysis
Overlay Operations
Spatial Interpolation
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Analysis of Models of
Surfaces and
Networks
Estimating values at unsampled
locations.
Often used to produce contour
surfaces.
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Data formed is only an estimate.
GIS software offer interpolation
schemes.
Spatial Interpolation Techniques
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Thiessen Polygons.
Data Point
Interpolated Surface -Thiessen Polygons
Original Elevation Surface Interpolated Surface
Thiessen Polygons
w/Sample Points
Spatial Interpolation Techniques
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Thiessen Polygons.
Triangular Irregular Networks
– TINS.
Interpolated Elevation - TIN
Original Elevation Surface
w/Sample Points
Interpolated Elevation
TIN
Spatial Interpolation Techniques
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Thiessen Polygons.
Triangular Irregular Networks – TINS.
Distance Weighting Function –
Spatial Moving Average.
Z0 =
zi(1/di )
2
n
i=1∑ (1/di )
i=1
∑n
2
Interpolated Elevation
Distance Weighted Average
Original Elevation Surface
w/Sample Points
Interpolated Elevation
Distance Weighted Average
Analysis of Surfaces
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DTM Surfaces
Slope/Aspect
Visibility
Analysis of Surfaces
Slope/Aspect
S
c
Slope:
b
θ in degrees, radians
Tan(θ)=c/b
θ
tan (θ) = rise/run = c/b
% = 100 Tan(θ)
θ
N
Analysis of Surfaces
Slope/Aspect
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Raster DTM
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3x3 Window
Determine the Best Fit tilted plane
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Slope Line
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S2= b2 + c2
Slope Gradient Angle (Slope)
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z = a + bx + cy
A = tan-1 (c/b)
Aspect – Horizontal angle measured to
horizontal projection of slope line.
Slope and Aspect
Surfaces
South Facing
North Facing
Flat
Steep
Visibility Analysis
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Line drawn from observer to other
points.
Ray Tracing finds blockage areas.
Repeated ray tracing around
observation point – Viewshed.
Ray Tracing for Visibility Analysis
Viewshed Analysis
Network Analysis
A set of interconnected lines
through which resources can flow.
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Most Applications – Road Networks
Impedance Values
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Network links
Turns
One way or closed streets
Overpasses and Underpasses.
Network Example
Find the Shortest Path between Cities
1 and 6
(20)
2
(39)
1
(53)
(58)
X = City Number
3
(25)
(19)
6
4
(13)
5
(13)
(Y) = Impedance in
Minutes
Shortest Path Example
Impedance in Minutes
(20)
2
(39)
1
(2) 20
(53)
(58)
3
(25)
(19)
6
4
(13)
5
(13)
(1) (2) (3) (4) (5) (6)
(1) 0 20 53 58 0 0
Cities
0
39
0
0
0
(3) 53 39
0
25
0
19
(4) 58
0
25
0
13
0
(5)
0
0
0
13
0
13
(6)
0
0
19
0
13
0
Cartographic Model
Formulation
Problem: Find a suitable site to store
nuclear waste
Criteria:
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Suitable geology
Away from high concentrations of
population
Away from major roads
Cannot be located in Conservation Area
Original
Data
QUERY
QUERY
G
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S
P
r
o
c
e
s
s
Final Map
Cartographic Model
Answer to
Problem
Summary
Data Analysis Operations – turning data
into information
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




Measurement Techniques
Attribute Queries
Proximity Analysis
Overlay Operations
Analysis of Models of Surfaces and
Networks
Cartographic Model
What’s Next
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Up to now – Data
Formation/Data Analysis
Next – Semester Project