Working with Routes and Linear Referencing in ArcGIS

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Presentation Objectives
Working with Linear Referencing and Route Events
Data Clean-up for Linear Features
Creating and Editing Topology and Routes
Analysis with Routes
Copyright 2013 – John SchaefferJuniper GIS
Working with Linear Referencing and Routes
Developed and Presented by Juniper GIS
PowerPoint available at www.junipergis.comLinks

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Understanding Linear Referencing
Linear Referencing Basics
Allows us to store location as a one-dimensional measure relative to the
location along a linear feature
These locations are
referred to as “Events”
and the process of
displaying these events
is called
Dynamic Segmentation.


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These events can be linear, located using From and To measures,
or points, located with a single measure.
These events are stored
in a table; with a reference
to the linear feature being
measured and the
measure value or values.

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Linear Referencing allows us
to use multiple tables, locating
a variety of different types of
information, along the same
linear feature.

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Without linear referencing, we would need to split data into separate
feature classes for each activity we wanted to measure.
Any time you needed to edit an activity, you might need to edit several feature
classes, but with linear referencing, you would just edit one table.

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Another way to describe
these events is as
‘Virtual Layers’
displayed as needed,
within ArcMap.
These events can be used
in analysis similar to
other layers in ArcMap.
These events can be
exported as actual
feature classes.

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Creating Routes
Routes are a special type of linear feature class that contain direction
and measure values, with the measure value, such as feet, miles,
river kilometers, increasing in one direction.
Shape field shows
the geometry type
as PolylineM.
Routes can be
created as shapefiles
or geodatabase
feature classes.

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Creating Routes
Routes can be created from an
existing feature class with the
Create Routes tool.
This requires a field that identifies
all the segments that will be an
individual route.
Routes need to have a defined
measurement source.
This can be the geometric length
as calculated by ArcMap, or a
field with the measured length.

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Creating Routes
Routes need to have a
‘Starting Point’ and direction.
If there are existing measures
ArcMap can determine
start & direction of routes.
If not, you can use
Coordinate Priority - upper-left,
lower-left, etc. - to assign a
starting point and direction.

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Creating Routes
Coordinate Priority only works well if all features are going the same direction

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Creating Routes
Routes might need a measure factor if the
measurement value is different from the feature’s unit value.
For example, the units for a stream
feature class are in meters, but we want
the measurement value to be in kilometers.

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Creating Routes
Routes can deal with spatial gaps, or how you measure gaps in
segments.
The default is to ignore the gaps and to continue the measurement
values as if the gap did not exist. If unchecked, then a straight-line
distance is used to adjust the route measurements for the gap.

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Creating Routes
Routes can also be created from
individual line segments with the
Make Route tool.
This is done in an editing session
and requires an existing route
feature class as a template.
The route feature class can be
an empty feature class or could
be a feature class that already
contains routes.

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Creating Routes
After selecting the feature or
features, click on the Make
Route tool and you’ll be
prompted for a starting point,
a measure value and a
measure factor.
This can be used as a quick
way to ‘recreate’ routes that
were created going in the
wrong direction.

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Working with Route Layers
Routes are similar to other data layers and can be manipulated using
layer properties. Route layers have two additional tabs.
Routes Tab – used to
display route measure
anomalies or to see
where problems
might exist.

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Working with Route Layers
Hatches Tab – used to
display measurement
markers.

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Displaying Route Events
Once routes have been created,
information in event tables that
reference routes can be displayed.
Events can be either point
events, such as sign locations, or
linear events such as
change in ownership or
condition over a distance.

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Displaying Route Events
This creates ‘virtual layers’ that
exist in that map, that act like
regular data layers, and can
be exported as feature classes.
If the underlying data table or
routes change, the displayed data
changes accordingly.

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Displaying Route Events – Route Errors
In 10, the table for route events shows all
input records, even those that don’t display
because of location errors.
In 10.1, the table only shows “good”
points. To fix this quirk, right-click the Loc_Error
field; select Sort Ascending, and you will see all
records, including those with errors. This is
needed to find and repair errors.

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Data Clean-up for Routes
Very important to have clean linear features before you create routes.
If you have ArcEditor, you can create Geodatabase Topology to
check for common errors.
Dangles
Pseudos
Overlaps
Intersecting lines
Multipart lines

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Editing and Using Routes for Analysis
Editing Routes
The most common edit to route features will be to adjust route measures.
Route measures are usually based on the length calculated by GIS.
If there are more accurate measurements, these can be used to
adjust the measures along the entire route, or in just a small section.
Errors in measurement values can also be introduced when features
are extended, merged, intersected or unioned.

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Route Editing Tools
Route Editing Toolbar
Calibrate Route Tool
– works in conjunction with the Calibrate Route Feature
task. Select a route and then click on a point where you
need to adjust a measure.
The other measures in that route or portion of the route can
then be interpolated or extrapolated as needed.
Works best if you identify at least two points.

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Route Editing Tools
Identify Route Locations Tool – similar to the Identify Tool, but works with
routes and displays measurement values and other information on a route.
This tool is very helpful when checking route measures before or after
calibrating routes. This tool has to be added to the Route Editing Toolbar.

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Route Editing Tools
Linear Referencing Tools
The Calibrate Routes tool creates a
new route feature class by calibrating
an existing route feature class based
on points that contain more
accurate measurements.
For best results the points should be
on or very near the routes.

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Using Routes for Analysis
Most analysis is actually based on the ‘events’ located along the
route rather than the route itself.
Since the event layers act
as any other layer, the normal
analysis tools you might use apply,
as well as some of the tools in the
Linear Referencing Toolset.

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Dissolve Feature Events –
Creates a new event table that removes
redundant information or separates
event tables into separate tables when they
have more than one descriptive attribute.

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Overlay Route Events
Overlays two event tables to create an output
event table that represents the union
or intersection of the input.

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Transform Route Events
Creates a new event table by transforming
the measures of events from one route
reference to another route reference.
This is useful if you need to transfer measures
or route ids from one event table to another.

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Locate Features Along Routes
Creates a new event table with route and
measure information by intersecting input
features (point, line, or polygon) with routes.

http://www.junipergis.com/gis-links/presentations/
Linear Referencing
Editing Tips
Spatial Analyst and Raster Analysis
Geodatabase Topology
Suitability Modeling
ModelBuilder
Using the Query Builder
Projections on U Tube
Other Presentations
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Working with Routes and Linear Referencing in ArcGIS

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