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 Schaeffer\Juniper GIS

Working with Linear Referencing and Routes

Developed and Presented by Juniper GISPowerPoint available at www.junipergis.com\Links

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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 arereferred 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 referenceto the linear feature beingmeasured and themeasure value or values.

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Linear Referencing allows us to use multiple tables, locating a variety of different types ofinformation, along the samelinear feature.

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Without linear referencing, we would need to split data into separatefeature 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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Understanding Linear Referencing Working with Linear Referencing and Routes



Another way to describethese events is as‘Virtual Layers’ displayed as needed, within ArcMap.

These events can be used in analysis similar toother 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 theCreate 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 streamfeature class are in meters, but we wantthe 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 usinglayer 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 Working with Linear Referencing and Routes

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 removesredundant 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 transformingthe 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/

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ModelBuilder

Using the Query Builder

Projections on U Tube

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Working with Routes and Linear Referencing in ArcGIS

Technology

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