1. LINEAR REFERENCING
In Arc GIS Version 9.3

2. Institute of Geology, University of the Punjab
Tuesday, January 28, 2014
Linear Referencing
Presented To:
Sir. Numan Ashraf
Submitted By:
Abdul Haseeb Ahson
Atiqa Ijaz Khan
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3. Institute of Geology, University of the Punjab
Table Of Contents
1. What is Linear Referencing?
2. Implementation in Arc GIS
3. Why Use Linear Referencing?
4. Route
5. Event Table
6. Dynamic Segmentation
7. Working with Arc GIS
8. Summary
9. References
Tuesday, January 28, 2014
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4. 4
What Is Linear Referencing?
1. “It is the method of storing geographic locations by using relative positions along a measured
linear feature.”
2. In linear referencing, location is given in terms of:
a. a known line feature and a position,
b. or measure, along the feature.
3. The method provides the ability to uniquely identify positions along lines without explicit x,y
coordinates.
Institute of Geology, University of the Punjab
Tuesday, January 28, 2014

5. 5
Modeling Of Data In Arc GIS
1. In Arc GIS, geographic data is stored in three ways:
a. As a collection of features in a Vector format.
b. As an array of cells in Raster format.
c. As a set of triangulated points in TIN.
Talking about the Vector Data Format Only… !
Institute of Geology, University of the Punjab
Tuesday, January 28, 2014

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Why Use Linear Referencing?
1. As we know that In the vector format, each feature has a geometry associated with it. Each
geometry is composed of two dimensional (x,y) or three dimensional (x,y,z) coordinates.
2. Many organizations collect data about the linear features as a point location along the line as
an alternative to expressing the location using xy-coordinates.
3. While the vector data is useful for the representation of the “Static Data”, like, water bodies,
parcel boundaries etc.
4. Also used to associate the multiple-attributes to a set of linear features, without splitting.
Institute of Geology, University of the Punjab
Tuesday, January 28, 2014

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
mile 5
30o40’25’’N, 96o22’32’’W

• E.g.,
The concrete road surface starts at mile
NOT The concrete road surface starts at 30o40’25’’N, 96o22’32’’W.
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Tuesday, January 28, 2014

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Accident
occurred 50
meters along
Main St.
Main St
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20
40
60
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• Features using a linear system of measure.
• Feature’s location determined using a linear system of measure values, instead of using
x,y coordinates.
Institute of Geology, University of the Punjab
Tuesday, January 28, 2014

9. 9
• Features containing frequently segmented data.
• Some types of features have attributes that change frequently.
Institute of Geology, University of the Punjab
Tuesday, January 28, 2014

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Implementation In Arc GIS
1.
Primary Data Types:
a. Route Feature Classes
b. Event Tables
2. Process: Dynamic Segmentation
a. Line feature from a route feature class
b. Events from event table are located in line feature
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Tuesday, January 28, 2014

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Route
2. “A Route is a path through a network.”
3. Routes are stored in a feature class whose geometry type is “Polyline”.
4. By definition: “A polyline is an ordered collection of paths.”
5. Polylines with measures are stored as polyline-M type.
6. Measure values are ONLY stored in Vertex (for Polyline also). Between
them, the data is interpolated.
Institute of Geology, University of the Punjab
Tuesday, January 28, 2014

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1.
“A route is a linear feature that has:
a. A unique identifier and
b. A measurement.”
Route
711081
Linear
feature
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Unique
identifier
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Measurements of Route
1. “Measures are the Distance along a Route from an Origin”
2. The measures are independent of the underlying feature geometry.
a. If the data is in UTM, then its measure values can be in feet or inches etc
3. They can, along a route, increase, decrease, or remain the same.
4. The measures are stored as long binary data (i.e. x,y,m) OR (i.e. x,y,z, and m)
5. By definition, the measures are common to all routes in the
feature class.
Institute of Geology, University of the Punjab
Tuesday, January 28, 2014

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Transportation
Accidents
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Speed
Railroad
0
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20
45
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60
55
80
100
• Features containing one-to-many relationships
• Two or more pieces of information associated with the same location on a line
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Tuesday, January 28, 2014

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Event Tables
1. Events are geographic location stored in “Tabular” rather than “Spatial” form.
2. Event types include address events, route events, xy events, and temporal events.
3. Specifically, route events can be linear, continuous, or point features occurring along a base
route system.
4. Route locations thematically stored in tables are called “Route Events” or simply “Events”.
5. Two types:
• Point Event Table
• E.g., Accidents, Sample sites
• Line Event Table
• E.g., Pavement conditions, Riverbank composition
Institute of Geology, University of the Punjab
Tuesday, January 28, 2014

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I10
Accident occurred at mile 23
Kenai River
Salmon found between
mile 10 and mile 20
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Tuesday, January 28, 2014

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Point Event Tables
1.
“A feature that occurs at a precise point location along a route and uses a single measure
value.”
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2. Two required fields:
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• Route ID identifies route on which event is located
• Measure is the event’s location on the route
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Route location
Attributes
3. Other attributes about the event.
Route 1
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4
0
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Tuesday, January 28, 2014

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Tuesday, January 28, 2014

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Line Event Tables
1. “Linear events are used to model portions of routes and are stored in tables.”
2. Three required fields
• Route ID identifies route on which event is located
• From Measure and To Measure define beginning and end of line event
3. Other attributes about the event
Route location
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Route 48
Attributes
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0
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Tuesday, January 28, 2014
0

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Tuesday, January 28, 2014

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1. A “Point event” describes a discrete location along a route (a point), whereas
2. A “Line event” describes a portion of a route (a line).
3. All of the data is important, but to segment the linear data (geometry) to create a “Break”
or “Segment” every time a change occurs is not an efficient way to store or manage the
dataset.
This Lead us to the Concept of “Dynamic Segmentation”
Institute of Geology, University of the Punjab
Tuesday, January 28, 2014

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Dynamic Segmentation
1.
There are Two requirements for dynamic segmentation:
a. A table of events that include a unique identifier and associated measures,
b. And a collection of linear features that include a unique identifier and a measurement
system.
2. Dynamic segmentation is the process of computing map location of events. Events are stored
and managed in an event table. The linear referencing measurement system is used to
display events on a map.
Institute of Geology, University of the Punjab
Tuesday, January 28, 2014

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Tuesday, January 28, 2014

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Benefits of Dynamic Segmentation
1. Multiple sets of attributes can be associated with any portion of an existing linear feature.
2. More importantly, attributes may be displayed, queried,
edited and analyzed without affecting the underlying linear feature geometry
3. The use of linear referencing permits you to dynamically locate a segment, without the
need to edit feature data geometry resulting in more efficient data management.
Institute of Geology, University of the Punjab
Tuesday, January 28, 2014

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Working with Arc GIS 9.3
1. Following are the sub-set tools in Arc GIS 9.3 Toolbox for Linear Referencing Tools:
a. Calibrate Routes
b. Create Routes
c. Dissolve Route Events
d. Locate Features along the Routes
e. Make Route Event Layer
f. Overlay Route Events
g. Transform Route Events
Institute of Geology, University of the Punjab
Tuesday, January 28, 2014

26. Institute of Geology, University of the Punjab
Tuesday, January 28, 2014
Data for Practice
1. Utah (USA) Road And Highway System
2. In Geo-database Fomrat
3. Coordinate System: NAD 1983
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Create Routes
* So to have
the options of
Route
Properties
Institute of Geology, University of the Punjab
Tuesday, January 28, 2014

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Tuesday, January 28, 2014

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Calibrate Routes
* For just to
have an
update
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Tuesday, January 28, 2014

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Tuesday, January 28, 2014

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Tuesday, January 28, 2014

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Institute of Geology, University of the Punjab
Tuesday, January 28, 2014

33. Dissolve Route Events
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* For
division of
event
table
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Tuesday, January 28, 2014

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Institute of Geology, University of the Punjab
Tuesday, January 28, 2014

35. Locate Feature Along Route
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* Pick those
points that
intersects
the linear
feature
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Tuesday, January 28, 2014

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Output
Input Points
Input Lines
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Tuesday, January 28, 2014

37. Make Route Event Layer
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Tuesday, January 28, 2014

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Institute of Geology, University of the Punjab
Tuesday, January 28, 2014

39. Overlay Events
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* Overlays
two event
table on
the basis of
their
unique ID
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Tuesday, January 28, 2014

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Input_1
Input_2
Overlay Output
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Tuesday, January 28, 2014

41. Transform Route Events
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Sample_Example
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Summary
Tool
Input_1
Input_2
Input_3
Output
Create Route
.shp / .dbf
-
-
Route .shp /.dbf
Calibrate Route
Route .shp /.dbf
Point/line .shp /.dbf
Dissolve Route
Events
Table
Unique ID
Dissolve Field
Event Table
Make Route
Event Layer
Route .shp /.dbf
Event Table
-
Table & .lyr
Locate Feature
Along the Route
.shp / .dbf
Route .shp /.dbf
Event Table OR
.dbf
Overlay Route
Event
Event Table
Event Table
Event Table
Transform
Route Events
Event Table
.shp / .dbf
Institute of Geology, University of the Punjab
.shp /.dbf
.sh / .dbf
Event table
Tuesday, January 28, 2014

44. Tuesday, January 28, 2014
Institute of Geology, University of the Punjab
References
1.
2.
3.
4.
5.
Linear Referencing in Arc GIS Tutorial PDF
Linear Referencing by: Christopher Grasteit, Technical Marketing
Working with Linear Referencing and Routes, by: www.junipergis.comlinks
www.help.arcgis.com
www.rnr/geog420/520 (Spring 2008)
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45. Institute of Geology, University of the Punjab
Tuesday, January 28, 2014
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