@2007 Austin Troy

Lecture 4: An Introduction to the Vector Data Model and Map

Layout Techniques

Introduction to GIS

By Brian VoigtUniversity of Vermont

Thanks are due to Dr Troy and Dr Zhou, upon whose lecture much of this material is based.

@2007 Austin Troy

1. Vector Data Model

Introduction to GIS

@2007 Austin Troy

• Three basic “feature” or “object” types– Point

– Arc

– Polygon

• A layer holds a single feature type

Reviewing Vector Data Types

Introduction to GIS

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• Attribute table

• Attribute types– Nominal attributes: descriptive information– Ordinal attributes: rank order or scale– Interval/ratio attributes: numeric items, order,

magnitude of difference

Reviewing Vector Data Types

Introduction to GIS

@2007 Austin Troy

Point Feature• A point layer: a collection of records with (x,y) coordinates

Introduction to GIS

Image modified from ESRI Arc Info electronic help

0 1 2 3 4 5 60

1

2

3

4

5

6

2,2

6,3

5,5

3,6

1

2

3

4

ID X,Y Coordinat

es1 2,2

2 3,6

3 5,5

4 6,3

…

10 4,1

4,110

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Line (Arc) Feature• Feature has length but not area• Straight or curved• Lines connect a set of vertices and nodes• Feature is the ARC, not the line segments• Arcs meet at nodes

Introduction to GIS

Image modified from ESRI Arc Info electronic help

Line segment

Node

Vertices

Node

@2007 Austin Troy

Line (Arc) Feature• Each point has a unique location

Introduction to GIS

@2007 Austin Troy

Polygon Feature• Area of homogenous phenomena • In a polygon layer, lines (arcs) define areas• Closed region – first and last coordinate pairs are in the

same location• Line segments bound the polygon

Introduction to GIS

Lines (Arcs)

Points

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• Definition1: Explicit encoding of spatial relationships between objects: the spatial location of each point, line and polygon is defined in relation to each other

Introduction to GIS

Topology

• Definition2: Topology is a collection of rules and relationships that enables the geodatabase to more accurately model geometric relationships found in the world.

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• Two major purposes

Introduction to GIS

Why Topology

– Allows for powerful analysis tools

– Quality control mechanism

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• Arc-node topology

Introduction to GIS

Types of Vector Topology

• Polygon topology

• Route topology

• Region topology

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• Connectivity analysis

Introduction to GIS

Arc-node & Node Topology

Arc-node Topology Arc-node List

Image source: ESRI Arc Info electronic help

Direction

@2007 Austin Troy

Polygon-arc Topology

Introduction to GIS

Polygon-arc Topology

Polygon-arc List

The order does matter!

Image source: ESRI Arc Info electronic help

@2007 Austin Troy

• Adjacency

Introduction to GIS

Polygon-arc Topology

External polygon

Image source: ESRI Arc Info electronic help

@2007 Austin Troy

Introduction to GIS

Route Topology• Define paths based on series of arcs

Image source: ESRI Arc Info electronic help

@2007 Austin Troy

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• Ensuring “logical consistency”– Define complex and nuanced rules governing

spatial relationships of features

• Data quality– Single layer quality control– Mutli-Layer quality control

Introduction to GIS

Quality control and topology

@2007 Austin Troy

• Say we have the following layers: parcels, sidewalks, right of way boundaries, building footprints, zoning

• Rules for spatial relationships– Lots must be enclosed polygons

– Buildings must be entirely within a lot

– Sidewalks must be outside a parcel polygon and entirely within the public right of way

– Lots must fall entirely within a single zoning class

– All lots must have access to a right of way

Introduction to GIS

Topology rules: Example

@2007 Austin Troy

Introduction to GIS

sliver polygon

does not share a border

• Single layer quality control

Quality control and topology

Dangles

undershoot

overshoot

@2007 Austin Troy

Introduction to GIS

• Multi-Layer quality control: Defining spatial rules between layers

Quality control and topology

– Polygon rules: e.g. Must Be Covered by Feature Class of

• ArcCatalog includes new tools for defining and validating topology rules (Book: Building a geodatabase)

– Line rules: e.g. Must not Self Intersect

– Point rules: e.g. Must be Properly Inside Polygons

@2007 Austin Troy

Spaghetti Data Model• Non-topological data model

Introduction to GIS

• Collections of line segments and points– Only stores features’ coordinates

– No real connection, topology or relationships

• Not for spatial analysis

• Generally come from CAD files or digitizing

• Can “clean” these data, using user-defined tolerances

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2. Map Layouts and Cartographic Representation

Introduction to GIS

@2007 Austin Troy

Introduction to GIS

Map Composition

Map?X

Map Elements?

@2007 Austin Troy

Introduction to GIS

Title

Legend

Neatline

North arrow

Scale bar

Notes

Data frame

Map Composition

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Layouts• Create a map for layout in ArcMap Layout view

View>>Layout view.

Introduction to GIS

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Introduction to GIS

Map Compilation• Geographic features

• Other map elements– Legend

– Title

– North arrow

– Scale bar

– Author

– Neatline

– Source of data

– Other objects…

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Layouts

Introduction to GIS

Give a title, e.g. land use

Symbol editing

• Legends are edited in the Legends property window: Accessed by double clicking the legends.

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Layouts

Introduction to GIS

• Legends editing: Items

Item

Style

Symbol

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Layouts

Introduction to GIS

• Legends editing: Frame

Frame

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Layouts

Introduction to GIS

• Legends editing: Size and position

Size&Position

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ArcMap: data frame• More than one frame can be shown in layout view

Introduction to GIS

Frame 1

Frame 2

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Layouts: data frame• Create a new view or “data frame” in ArcMap

Introduction to GIS

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Layouts: data frame• Access and edit data frame properties

Introduction to GIS

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MXD Files

Introduction to GIS

• Mxd files are project files

– Save your layout

– All other preferences

– Data is not included

– With an extension .mxd

•File >> Save (As)

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Layer Files

Introduction to GIS

• Save symbology and setting

• Primarily for saving legend setting

• Opening a layer file will open the data layer with all the preferences saved

• With an extension .lyr

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Layer Files

Introduction to GIS

• Use layer files when you have lots of non-numeric categories

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Layer Files

Introduction to GIS

• Create a layer file in ArcCatalog

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Layer Files

Introduction to GIS

• Create a layer file in ArcMap

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Layer Files

Introduction to GIS

• Import a layer file’s symbology in properties

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Layer Package Files

Introduction to GIS

• Save symbology and settings AND the data!

• New at version 9.3.1

• With an extension .lpk

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Layer Package Files

Introduction to GIS

Double-click the file to open in ArcMap or ArcCatalog