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Linear Referencing An Introduction

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 Referencing An Introduction

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  1. Linear ReferencingAn Introduction Heather McCracken & Derek LawESRI Redlands UC 2009 Tech Sessions

  2. Outline • Fundamental concepts • Terminology in ArcGIS • Query & analysis operations • Creating & maintaining routes • Summary UC 2007 Tech Sessions

  3. Outline • Fundamental concepts • Define linear referencing • Application examples • Terminology in ArcGIS • Query & analysis operations • Creating & maintaining routes • Summary UC 2007 Tech Sessions

  4. A45 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

  5. mile 5 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

  6. Accident occurred 50 meters along Main St. 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

  7. Accidents 45 35 45 55 Speed Railroad 0 40 80 20 60 100 Slow Rapid Gradient 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

  8. 15 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

  9. Outline • Fundamental concepts • Terminology in ArcGIS • Routes • Measures • Events • Dynamic segmentation • Query & analysis operations • Creating & maintaining routes • Summary UC 2007 Tech Sessions

  10. 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

  11. Single part polyline Multi-part polyline Looping Branching 180-degree turns Route geometry and what can they model • Route geometry • Routes can model UC 2007 Tech Sessions

  12. Routes in ArcMap • Layer properties > Route tab • Route Identifier • Uniquely identifies each route • Used by all other linear referencing dialogs in ArcGIS UC 2007 Tech Sessions

  13. 4.2 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

  14. I10 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

  15. Event tables • 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

  16. 60 53 45 Route location Attributes 34 Route 1 14 4 0 Point event tables • Two required fields • 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

  17. 60 Route 48 Route location Attributes 25 0 0 Line event tables • Three required fields • 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

  18. A45 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

  19. Event layers are feature layers • 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

  20. Demo 1 Routes, measures, events& dynamic segmentation UC 2007 Tech Sessions

  21. Outline • Fundamental concepts • Terminology in ArcGIS • Query & analysis operations • Route query • Route symbolization options • Route events analysis • Creating & maintaining routes • Summary UC 2007 Tech Sessions

  22. Find and Identify route locations 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

  23. Seismic lines 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

  24. Route event analysis tools • Overlay events • Dissolve/concatenate events • Transform events • Locate points & polygonsalong routes UC 2007 Tech Sessions

  25. Accident count 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

  26. Dissolve/concatenate events • Concatenate:remove redundant information from a table • Dissolve:split tables having more than one descriptive attribute UC 2007 Tech Sessions

  27. Transform events • 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

  28. 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

  29. Route location 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

  30. Demo 2 Find & identify route locationsRoute event analysis UC 2007 Tech Sessions

  31. Outline • Fundamental concepts • Terminology in ArcGIS • Query & analysis operations • Creating & maintaining routes • Creating routes • Calibrating routes • Editing routes • Summary UC 2007 Tech Sessions

  32. Creating routes • 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 empty feature class & loading data • 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

  33. Define route identifier field 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

  34. Input features 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

  35. Points with measures 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

  36. Sketch Properties Route Editing toolbar Define line portion Calibrate Route Tasks for linear referencing Make Route Editing routes • Edit routes just like any polyline • Extend, delete, split, etc Editing toolbar A UC 2007 Tech Sessions

  37. Demo 3 Create a route feature class,then calibrate its M values UC 2007 Tech Sessions

  38. Summary • 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 • Please complete review surveys UC 2007 Tech Sessions

  39. Questions? UC 2007 Tech Sessions

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