an overview of the chester county local linear referencing system (lrs)
DESCRIPTION
An Overview of the Chester County Local Linear Referencing System (LRS). What is an LRS?. Most generally, a linear referencing system comprises: Selected linear features of an agency’s centerline aggregated into routes that represent distinct paths where travel can, does or will occur. - PowerPoint PPT PresentationTRANSCRIPT
![Page 1: An Overview of the Chester County Local Linear Referencing System (LRS)](https://reader035.vdocument.in/reader035/viewer/2022062518/5681491e550346895db6590c/html5/thumbnails/1.jpg)
An Overview of the Chester CountyLocal Linear Referencing System (LRS)
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What is an LRS?
Most generally, a linear referencing system comprises:
1) Selected linear features of an agency’s centerline aggregated into routes that represent distinct paths where travel can, does or will occur.
For the regional GIS-T the focus is existing street centerline
2) Measure values (in feet for the PA regional GIS-T) applied along these routes – consistently ascending from one end to the other and no redundancy.
3) Linear or point representations of Spatial and/or Attribute data related to these routes and measures; referenced by event tables.
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Evaluation and Preparation of thepre-local LRS Centerline File
Chester County non-local LRS transportation centerline (TCL):
1. “Native” County Centerline (CL) consists of street (and limited trail) segmented and attributed according to requirements of emergency services and addressing. Spatially accurate with a few known exceptions.
2. Digitized direction of segments runs with increasing addresses (or travel direction on dual-centerline freeway) Ramps generally not part of native ChesCo CL: added to TCL
3. TCL maintained as network – with Junctions feature class (FC) – in feature dataset.
4. Native ChesCo CL – and now TCL – verified as 100% topologically correct (according to rules elsewhere described).
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Chester County non-local LRS TCL Example # 1:PennDOT LRS supported on spatially accurate ChesCo CL, TCL includes all public roads and ties to County data.
Pre-local LRS File Evaluation and Preparation (cont.)
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Step 2: Assignment of segments to routes cont
Example of correct route definition (route color by local route ID)
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In contrast to the muni-line road illustrated on the previous slide, Berwyn Paoli Rd must change route ID because Tredyffrin has the higher PennDOT code.
Step 2: Assignment of segments to routes cont
Example of correct route definition (muni-line roads)
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Same name & muni, but not continuous
Directional Prefix change
Step 2: Assignment of segments to routes cont
Example of correct route definition: reasons for breaking routes
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Six segments named Esprit TC No more than four can be strung together to form a route Several options for route definition Best (?) solution leaves two single standalone segment routes (other “correct” options are possible)
Subjective Route Definition ChoiceWhen same-name/same muni streets intersect
Step 2: Assignment of segments to routes cont
Option 5
Option 2
Option 3
Option 4
Option 1(selected
)
There is no need to waste time analyzing the comparative merits of one route definition over another. Just make sure your method produces a result that is acceptable by the route-definition rules.
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Step 2: Assignment of segments to routes cont
Examples of route definition and Route Names/ID’s
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Step 2: Assignment of segments to routes cont
Example of route definition and measure for routes that begin and/or end with a loop segment.
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Route-data Table(s), ID’s and Attributes
A master route table(s) for all routes (local, PennDOT …)
1) Ensures that all route ID’s are unique and valid;
2) Maintains referential integrity with regard to segments’ route attributes;
3) Lets you join centerline segments to their route data.
The Transportation Centerline feature class table includes fields for all possible route ID’s
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Example of application of M-Values to Route Step 2: Assignment of segments to routes: suggested procedure
West Bradford’s Vermont Lane Route: Two segments – approx. 505’ Route runs EB, but Westernmost segment runs WB
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Multiple LRS optionsSupported by single underlying geometry
Single “Transportation
Centerline” Feature Class
PennDOT LRS Applied Local LRS Applied Other LRS Applied
• Rail station, mile marker, other agency measures, etc:
• All Linearly-referenced data transformable among LRS’s via common underlying geometry/ArcToolbox
Hybrid LRS Applied?
1) Fully-segmented, all inclusive FC (allows segment-specific event reference)
2) FC “dissolved” by applicable route ID’s after definition query is applied to extract only relevant segments (provides better performance)
OR
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Multiple LRS optionsSupported by single underlying geometry
Single “Transportation
Centerline” Feature Class
PennDOT LRS Applied Local LRS Applied
PennDOT measures by NLF
Local measures by local Route ID
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Local vs. PennDOT LRS on Same Centerline
• Routes Start in same place and run in same direction• M-values on both LRS’s are close through West Chester• New Local Route 52_0036 begins at municipal line, where as PennDOT NLF 2907 continues
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Local vs. PennDOT LRS ramps and divided highway
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Local Routes: Not just for streets• Rail (active, inactive, abandoned…)
• Non-motorized path (trail, multi-use path, etc)
• Waterway (navigable/for recreation)
• Inactive corridors (utility ROW’s, muni easements, railbanking …)
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Using the local LRSExample of route event source
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Using the local LRSExample of route event generation with custom application
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