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# Linear Referencing An Introduction - PowerPoint PPT Presentation

Linear Referencing An Introduction. Heather McCracken & Derek Law ESRI Redlands. Outline. Fundamental concepts Terminology in ArcGIS Query & analysis operations Creating & maintaining routes Summary. Outline. Fundamental concepts Define linear referencing Application examples

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### Linear ReferencingAn Introduction

Heather McCracken & Derek LawESRI Redlands

UC 2009 Tech Sessions

• Fundamental concepts

• Terminology in ArcGIS

• Query & analysis operations

• Creating & maintaining routes

• Summary

UC 2007 Tech Sessions

• Fundamental concepts

• Define linear referencing

• Application examples

• Terminology in ArcGIS

• Query & analysis operations

• Creating & maintaining routes

• Summary

UC 2007 Tech Sessions

D23

F478

A307

D23

B7

A307

B7

A45

F478

What is linear referencing?

• Method of storing geographic features by usingrelative positions along a measured line feature

A307 is 100 miles long. Where is mile 60?

A

UC 2007 Tech Sessions

30o40’25’’N, 96o22’32’’W

Why use linear referencing?

• Intuitive way to model relative locations alonglinear features

• E.g., The concrete road surface starts at mile 5,NOT The concrete road surface starts at 30o40’25’’N, 96o22’32’’W

• Enables the association of multiple sets of attributes to portions of linear features without segmenting the underlying line each time attribute values change

A

UC 2007 Tech Sessions

Main St

15

95

20

40

60

80

Features using a linear system of measure

• Feature’s location determined using a linear system of measure values, instead of using x,y coordinates

UC 2007 Tech Sessions

45

35

45

55

Speed

0

40

80

20

60

100

Slow

Rapid

Coho/King

Coho

Salmon habitat

200

400

River

600

500

0

100

300

Features containing one-to-many relationships

• Two or more pieces of information associated with the same location on a line

Transportation

Natural resources

UC 2007 Tech Sessions

95

20

40

60

80

concrete

asphalt

Material

good

poor

fair

Quality

Main St.

Features containing frequently segmented data

• Some types of features have attributes that change frequently

UC 2007 Tech Sessions

• Fundamental concepts

• Terminology in ArcGIS

• Routes

• Measures

• Events

• Dynamic segmentation

• Query & analysis operations

• Creating & maintaining routes

• Summary

UC 2007 Tech Sessions

Route 711081

Linear feature

Unique identifier

Routes

• Linear features – in a polyline feature class

• Must have an identifier & measurement system

• Store in a geodatabase, shapefile, or coverage

UC 2007 Tech Sessions

Multi-part polyline

Looping

Branching

180-degree turns

Route geometry and what can they model

• Route geometry

• Routes can model

UC 2007 Tech Sessions

• Layer properties > Route tab

• Route Identifier

• Uniquely identifies each route

• Used by all other linear referencing dialogs in ArcGIS

UC 2007 Tech Sessions

1.2

3.7

4.8

NaN

0.0

M at every vertex

Measures

• The distance along a route from an origin

• Can be miles, meters, feet, time

• Do not have to be the same units as the x,y coordinates

• Can increase, remain constant, or decrease

• Route vertices store measure values (M)

• NaN (unknown) measures may exist

• Not a Number

UC 2007 Tech Sessions

Accident occurred at mile 23

Kenai River

Salmon found between mile 10 and mile 20

Route locations

• Use a route identifier to locate the appropriate route

• 2 types

• Point (uses a single measure value)

• Discrete location on a route

• Line (uses from- and to- measure values)

• Describe a portion of a route

UC 2007 Tech Sessions

• Route locations thematically stored in tables are called “route events” or simply “events”

• 2 types

• Point event table

• E.g., Accidents, Sample sites

• Line event table

• E.g., Pavement conditions, Riverbank composition

• An event can be any type of table supported by ArcGIS

UC 2007 Tech Sessions

53

45

Route location

Attributes

34

Route 1

14

4

0

Point event tables

• Route ID identifies route on which event is located

• Measure is the event’s location on the route

• Other attributes about the event

UC 2007 Tech Sessions

Route 48

Route location

Attributes

25

0

0

Line event tables

• Route ID identifies route on which event is located

• From Measure and To Measure define beginning and end of line event

• Other attributes about the event

A

UC 2007 Tech Sessions

D23

F478

OID

RKEY

MILE

ACCTYPE

A307

0

A307

10.2

1

1

A307

15.5

1

B7

2

A307

25.6

0

3

F478

2.5

3

4

F478

9.5

2

5

A45

3.2

4

6

A45

7.1

4

Dynamic segmentation

• Computing the location of events on routes

• Event locations can change dynamically

• Locations are interpolated

• Use the MakeRouteEventLayer GP tool

UC 2007 Tech Sessions

• Created by the dynamic segmentation process

• Underlying route is not fragmented

• Event layers behave just like other feature layers

• Display using custom symbology

• Perform GIS analysis

• Save as a layer file

• Export to feature class

UC 2007 Tech Sessions

### Routes, measures, events& dynamic segmentation

UC 2007 Tech Sessions

• Fundamental concepts

• Terminology in ArcGIS

• Query & analysis operations

• Route query

• Route symbolization options

• Route events analysis

• Creating & maintaining routes

• Summary

UC 2007 Tech Sessions

Find:Query a map using a route location

Identify Route Locations: Click on map to determine route locations

Route: 13000C00158

Measure: 0.5

A

UC 2007 Tech Sessions

Hatch

Hatching

• Line or point marker symbols placed at an interval along a route

• Distance

• E.g., meters, feet

• Non-distance

• E.g, sample sites

• Create & modify hatch styles via style manager

• Import hatches from a layer file (.lyr)

• Convert hatches to graphics

UC 2007 Tech Sessions

• Overlay events

• Dissolve/concatenate events

• Transform events

• Locate points & polygonsalong routes

UC 2007 Tech Sessions

35

45

55

25

Speed limit

35

65

45

Pavement type

Asphalt

Asphalt

Concrete

Skid values

34

30

32

Result

Overlay events

• Logical union or intersection of two input event tables

• Creates new event table with attributes from both tables

• Non-geometric way of performing

• Line-on-line, line-on-point, & point-on-point overlays

GIS Query:Accident count > 50 Speed limit = 65 Pavement = Concrete Skid value >= 30

A

UC 2007 Tech Sessions

• Concatenate:remove redundant information from a table

• Dissolve:split tables having more than one descriptive attribute

UC 2007 Tech Sessions

• Transforms event measures from one route feature class to another

• Route feature classes can be of different measure systems (e.g., time & length)

• Creates a new event table

• Can update events after road realignments

UC 2007 Tech Sessions

Pointattributes

Route location

Optional distance field

Locate points along routes

• Create a point events table by locating the points along a route

• Preserves point attributes

• Route-to-point distance can be created

UC 2007 Tech Sessions

Polygon attributes

Locate polygons along routes

• Creates a line events table from the intersection of routes with polygons

• Preserves polygon attributes

UC 2007 Tech Sessions

### Find & identify route locationsRoute event analysis

UC 2007 Tech Sessions

• Fundamental concepts

• Terminology in ArcGIS

• Query & analysis operations

• Creating & maintaining routes

• Creating routes

• Calibrating routes

• Editing routes

• Summary

UC 2007 Tech Sessions

• Routes are created by

• Merging linear features based on common identifiers

• E.g., route ID

• Setting measures based on one or two fields

• Create routes

• By creating a new route feature class from existing line features

• By converting an existing route feature class

• Methods

• ArcToolbox (CreateRoutes & CalibrateRoutes GP tools)

• ArcCatalog

• ArcMap

UC 2007 Tech Sessions

Set geometry type

Enable M storage

Create a Route Feature Class from Scratch

• Follow standard procedures for creating a feature class

UC 2007 Tech Sessions

Route ID field

Output features

Measure field(s) or

Geometric Length

Create a route feature class from existing lines

• CreateRoutes GP tool

UC 2007 Tech Sessions

10

5

15

30

55.6

10

25

0.0

28.4

Existing vertex

Extrapolation

Calibrate

10

35.2

Extrapolation

15

30

5

25

20

1.1

New vertices createdwith interpolated measures

Existing vertex’s measure is interpolated

Calibrate route feature class

• Setting a route’s measurement system

A

UC 2007 Tech Sessions

Route Editing toolbar

Define line portion

Calibrate Route

Make Route

Editing routes

• Edit routes just like any polyline

• Extend, delete, split, etc

Editing toolbar

A

UC 2007 Tech Sessions

### Create a route feature class,then calibrate its M values

UC 2007 Tech Sessions

• Fundamental concepts

• Defined linear referencing and its applications

• Terminology in ArcGIS

• Routes, measures, events, & dynamic segmentation

• Query & analysis operations

• Simple querying, symbology, & analysis tools

• Creating & maintaining routes

• How to create, calibration, & editing