Linear Ref

1/18

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 2010 John Schaeffer

Working with Linear Referencing and Routes

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

2/18

Understanding Linear ReferencingWorking with Linear Referencing and Routes

Copyright 2010John Schaeffer\Juniper GIS

Linear Referencing Basics

Allows us to store location as a one-dimensional measure relative to the location along a linear feature

These locations are often referred to as Eventsand the process of displaying these events is sometimes called Dynamic Segmentation.

3/18




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.

4/18




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

Without linear referencing, we would need to splitdata into separatefeature classes foreach activity we wanted to measure.

5/18

Understanding Linear Referencing




One way to think about these events is that they are Virtual Layersdisplayed as needed, within ArcMap.

These events can then be used in analysis similar to any other layers in ArcMap.

These events can also be exported as actual feature layers

6/18




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.

7/18




Creating Routes

Routes can be created from an existing feature class using theCreate Routes tool.

Routes created from a feature class need a field that identifies all the segmentsthat will be an individual route.

Routes need to have a defined measurement source.

This can be the geometric length of the features as calculated by ArcMap, or a field that has the measured length.

8/18




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.

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

9/18




Creating Routes

Routes might need a measure factor if the measurement valueis different from the features unit value.

For example, the units for a streamfeature class are in meters, but we wantthe measurement value to be in kilometers.

10/18




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 this is unchecked, then astraight-line distance is used to adjust the route measurements for the gap.

11/18




Creating Routes

Routes can also be created from individual line segments using the Make Route tool.

This is done in an editing session and requires an existing route feature class, with that feature class being the Target layer.

The route feature class can be an empty feature class or could be an existing feature class that already contains routes.

12/18




Creating Routes

After selecting the feature or features feature class, click on the Make Route tool and youll 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.

13/18




Working with Route Layers

Routes are similar to other data layers and can be manipulated using thelayer properties. Route layers have two additional tabs in the Layer Properties dialog.

Routes Tab used to display route measure anomalies or to see where problems might exist.

14/18




Working with Route Layers

Hatches Tab used to display measurement markers.

15/18




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.

16/18




Displaying Route Events

This creates virtual layers that exist in that map session, 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.

17/18




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

18/18

DemonstrationCreating Topology & Routes

Using Linear Referencing to Locate Fish Observations



1/10

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 feature 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.


2/10



Route Editing Tools

Route Editing Toolbar

Calibrate Route Tool works in conjunction with the Calibrate Route Feature task. Select a route and then use the Sketch tool to 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.


3/10



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.


4/10



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 the more accurate measurements.

For best results the points should be on or very near the routes.


5/10



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.


6/10




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.


7/10




Overlay Route Events

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


8/10




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.


9/10




Locate Features Along Routes

Creates a new event table with route and measure information by intersecting input features (point, line, or polygon) with route features.


10/10-end

Demonstration: Editing and Using Routes for Analysis



Working with Linear Referencing and RoutesWorking with Linear Referencing and RoutesWorking with Linear Referencing and RoutesWorking with Linear Referencing and RoutesWorking with Linear Referencing and RoutesWorking with Linear Referencing and RoutesWorking with Linear Referencing and RoutesWorking with Linear Referencing and RoutesWorking with Linear Referencing and RoutesWorking with Linear Referencing and RoutesWorking with Linear Referencing and RoutesWorking with Linear Referencing and RoutesWorking with Linear Referencing and RoutesWorking with Linear Referencing and RoutesWorking with Linear Referencing and RoutesWorking with Linear Referencing and RoutesWorking with Linear Referencing and RoutesWorking with Linear Referencing and RoutesWorking with Linear Referencing and RoutesWorking with Linear Referencing and RoutesWorking with Linear Referencing and RoutesWorking with Linear Referencing and RoutesWorking with Linear Referencing and RoutesWorking with Linear Referencing and RoutesWorking with Linear Referencing and RoutesWorking with Linear Referencing and RoutesWorking with Linear Referencing and RoutesWorking with Linear Referencing and Routes

Documents

Linear Ref