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# Lecture 4: An Introduction to the Vector Data Model and Map Layout Techniques - PowerPoint PPT Presentation

Introduction to GIS. Lecture 4: An Introduction to the Vector Data Model and Map Layout Techniques. By Brian Voigt University of Vermont Thanks are due to Dr Troy and Dr Zhou, upon whose lecture much of this material is based. Introduction to GIS. 1. Vector Data Model. Introduction to GIS.

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

By Brian Voigt

University of Vermont

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

### 1. Vector Data Model

Reviewing Vector Data Types

• Three basic “feature” or “object” types

• Point

• Arc

• Polygon

• A layer holds a single feature type

Reviewing Vector Data Types

• Attribute table

• Attribute types

• Nominal attributes: descriptive information

• Ordinal attributes: rank order or scale

• Interval/ratio attributes: numeric items, order, magnitude of difference

Point Feature

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

6

2

3,6

5

3

5,5

4

3

4

6,3

2

1

2,2

1

10

4,1

0

0

1

2

3

4

5

6

Image modified from ESRI Arc Info electronic help

Line (Arc) Feature

• One or several line segments define an arc (straight or curved)

• 2 points define a line segment

• Line endpoints are nodes; angle points are vertices (sing. vertex)

• Arcs meet at nodes

• Feature is the ARC, not the line segments

• Feature has length but not area

Vertices

Line segment

Node

Node

Image modified from ESRI Arc Info electronic help

Line (Arc) Feature

• Each point has a unique location

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

Lines (Arcs)

Points

Topology

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

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

Why Topology

• Two major purposes

• Allows for powerful analysis tools

• Quality control mechanism

Types of Vector Topology

• Arc-node topology

• Polygon topology

• Route topology

• Region topology

Direction

Introduction to GIS

Arc-node & Node Topology

• Connectivity analysis

Arc-node Topology

Image source: ESRI Arc Info electronic help

The order does matter!

Introduction to GIS

Polygon-arcTopology

Polygon-arc Topology

Image source: ESRI Arc Info electronic help

Introduction to GIS

Polygon-arcTopology

Image source: ESRI Arc Info electronic help

Route Topology

• Define paths based on series of arcs

Image source: ESRI Arc Info electronic help

Quality control and topology

• Ensuring “logical consistency”

• Define complex and nuanced rules governing spatial relationships of features

• Data quality

• Single layer quality control

• Mutli-Layer quality control

undershoot

Introduction to GIS

Quality control and topology

• Single layer quality control

Dangles

sliver polygon

does not share a border

Quality control and topology

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

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

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

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

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

Topology rules: Example

• 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

### Spaghetti Data Model

• Collections of line segments and points

• Only stores features’ coordinates

• No real connection, topology or relationships

Non-topological data model

• Not for spatial analysis

• Generally come from CAD files or digitizing

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

### 2. Map Layouts and Cartographic Representation

Map Composition

X

Map?

Map Elements?

Legend

Neatline

Data frame

North arrow

Scale bar

Notes

Introduction to GIS

Map Composition

### Layouts

Create a map for layout in ArcMap Layout view View>>Layout view.

Map Compilation

• Geographic features

• Other map elements

• Legend

• Title

• North arrow

• Scale bar

• Author

• Neatline

• Source of data

• Other objects…

Insert Legend Title

Symbol editing

Introduction to GIS

Legends are edited in the Legends property window: Accessed by double clicking a legend.

### Layouts

Symbol

Introduction to GIS

Legend editing: Items

### Layouts

Items

Editing legend item style

Editing legend frame

### Layouts

Frame

Editing legend size and position

### Layouts

Size & Position

Layouts: data frame

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

ArcMap: data frame

• More than one frame can be shown in layout view

Frame 1

Frame 2

Data Frames: Inset maps

Layouts: data frame

Access and edit data frame properties

• Mxd files are project files

• All other preferences

• Data is not included

• With an extension .mxd

### MXD Files

• File >> Save (As)

• Save symbology and settings

• Primarily for saving legend settings

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

• With an extension .lyr

### Layer Files

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

### Layer Files

Create a layer file in ArcMap (also in ArcCatalog)

### Layer Files

Import a layer file’s symbology in properties

### Layer Files

• Save symbology and settings AND the data!

• With file extension .lpk

### Layer Package Files

Double-click the file to open in ArcMap or ArcCatalog