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Linear referencing

Linear referencing, also called linear reference system or linear referencing system (LRS), is a method of spatial referencing in engineering and construction, in which the locations of physical features along a linear element are described in terms of measurements from a fixed point, such as a milestone along a road. Each feature is located by either a point (e.g. a signpost) or a line (e.g. a no-passing zone). If a segment of the linear element or route is changed, only those locations on the changed segment need to be updated. Linear referencing is suitable for management of data related to linear features like roads, railways, oil and gas transmission pipelines, power and data transmission lines, and rivers.

A station number written on a silt fence at a construction site

Motivation

A system for identifying the location of pipeline features and characteristics is by measuring distance from the start of the pipeline. An example linear reference address is: Engineering Station 1145 + 86 on pipeline Alpha = 114,586 feet from the start of the pipeline. With a reroute, cumulative stationing might not be the same as engineering stationing, because of the addition of the extra pipeline. Linear referencing systems compute the differences to resolve this dilemma.

Linear referencing is one of a family of methods of expressing location. Coordinates such as latitude and longitude are another member of the family, as are landmark references such as "5 km south of Ayers Rock." Linear referencing has traditionally been the expression of choice in engineering applications such as road and pipeline maintenance. One can more realistically dispatch a worker to a bridge 12.7 km along a road from a reference point, rather than to a pair of coordinates or a landmark. The road serves as the reference frame, just as the earth serves as the reference frame for latitude and longitude.

Benefits

Linear referencing can be used to define points along a linear feature with just a small amount of information such as the name of a road and the distance and bearing from a landmark along the road. This information can be communicated concisely via plaintext. For example: "State route 4, 20 feet east of mile marker 187." Giving a latitude and longitude coordinate to a work crew is not meaningful unless the coordinate is plotted on a map. Often work crews work in remote areas without wireless connectivity which makes on-line digital maps not practical, and the relatively higher effort of providing offline maps or printed maps is not as economical as simply stating locations as offsets, or ranges of offsets, along a linear feature.

Linear referencing systems can also be made to be both very precise and very accurate at a much lower cost than is needed to collect latitude and longitude coordinates with high accuracy, especially when the goal is sub-meter accuracy. This is highly dependent upon the width of the linear feature, its centerline, and the visibility of the landmarks and markers that are used to define linear reference offsets.

Often, roads are created by engineers using CAD tools that have no geospatial reference at all, and LRS is the preferred method of defining data for linear features.

Limitations

Consequently, a major limitation of linear referencing is that specifying points that are not on a linear feature is troublesome and error-prone, though not entirely impossible. Consider for example a ski lodge located 100 meters to the right of the road, traveling north. The linear referencing system can be extended by specifying a lateral offset, but the absolute location (i.e. coordinates) of the lodge cannot be determined unless coordinates are specified for the road; that process is prone to error particularly on curved roads.

Another major drawback of linear referencing is that a modification in the alignment of a road (e.g. constructing a bypass around a town) changes the measurements that reference all downstream points. The system requires an extensive network of reference stations, and constant maintenance. In an era of mobile maps and GPS, this maintenance overhead for linear referencing systems challenges its long-term viability. (But see below for US Federal Highway Administration requirement that all State DOTs use LRS.)

Nonetheless, travel along a road is a linear experience, and at the very least, linear referencing will continue to have a conversational role. Linear referencing systems are recognized by the US Federal government as a valuable tool for specifying right of way data, and are now actually required for the States. Therefore, it is not likely to see LRS usage decline any time soon.

Applications

ARNOLD: US Federal Requirements for Highways

The US Federal Highway Administration is pushing states to move closer to standardization of LRS data with the ARNOLD requirement. To wit:

"On August 7, 2012, FHWA announced that the HPMS is expanding the requirement for State

Departments of Transportation (DOTs) to submit their LRS to include all public roads. This requirement

will be referred to as the All Road Network of Linear Referenced Data (ARNOLD)".[1]

The ARNOLD requirement sets the stage for systems that utilize both LRS and coordinates. Both systems are useful in different contexts, and while using latitude and longitude is becoming very popular due to the availability of practical and affordable devices for capturing and displaying global coordinate data, the use of LRS has widely been adopted for planning, engineering, and maintenance.

Supported platforms

Linear referencing is supported for example by several Geographic Information System software, including:

See also

References

  1. ^ "All Road Network of Linear Referenced Data (ARNOLD) Reference Manual" (PDF). Federal Highway Administration. Retrieved 15 November 2016.
  2. ^ Intergraph. "An LRS Model Supporting Event Location Stability and Temporal Data Management" (PDF). {{cite journal}}: Cite journal requires |journal= (help)
  3. ^ Intergraph. "White Paper: An Automated Approach to Managing Components of a Linear Reference System Network and Event Data" (PDF). {{cite journal}}: Cite journal requires |journal= (help)
  4. ^ Benefits "Smallworld Global Transmission Office". {{cite web}}: Check |url= value (help)
  5. ^ Esri (24 February 2009). "ArcGIS 9.3: An overview of linear referencing". Esri. Retrieved 8 March 2011.
  6. ^ Geomap Services (6 June 2011). . Geomap Services. Archived from the original on 25 April 2012. Retrieved 11 November 2011.
  7. ^ Radim Blazek (March 2005). "Introducing the Linear Reference System in GRASS" (PDF). International Journal of Geoinformatics. 1 (3). Retrieved 2007-05-01.
  8. ^ PostGIS team (2010). "PostGIS 1.5.2 Manual". Retrieved 8 March 2011.
  9. ^ "LRS Plugin for QGIS".

Further reading

  • Noronha, Val; Church, Richard L. (2002), (PDF), Santa Barbara, California: Vehicle Intelligence and Transportation Analysis Laboratory, National Center for Geographic Information and Analysis, archived from the original (PDF) on 20 July 2011, retrieved 8 March 2011
  • Curtin, K; Arifin, R; Nicoara, G (2007), (PDF), URISA Journal 19 (2), 41-50, archived from the original (PDF) on 2010-06-23

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This article includes a list of general references but it lacks sufficient corresponding inline citations Please help to improve this article by introducing more precise citations May 2016 Learn how and when to remove this template message Linear referencing also called linear reference system or linear referencing system LRS is a method of spatial referencing in engineering and construction in which the locations of physical features along a linear element are described in terms of measurements from a fixed point such as a milestone along a road Each feature is located by either a point e g a signpost or a line e g a no passing zone If a segment of the linear element or route is changed only those locations on the changed segment need to be updated Linear referencing is suitable for management of data related to linear features like roads railways oil and gas transmission pipelines power and data transmission lines and rivers A station number written on a silt fence at a construction site Contents 1 Motivation 2 Benefits 3 Limitations 4 Applications 4 1 ARNOLD US Federal Requirements for Highways 5 Supported platforms 6 See also 7 References 8 Further readingMotivation EditA system for identifying the location of pipeline features and characteristics is by measuring distance from the start of the pipeline An example linear reference address is Engineering Station 1145 86 on pipeline Alpha 114 586 feet from the start of the pipeline With a reroute cumulative stationing might not be the same as engineering stationing because of the addition of the extra pipeline Linear referencing systems compute the differences to resolve this dilemma Linear referencing is one of a family of methods of expressing location Coordinates such as latitude and longitude are another member of the family as are landmark references such as 5 km south of Ayers Rock Linear referencing has traditionally been the expression of choice in engineering applications such as road and pipeline maintenance One can more realistically dispatch a worker to a bridge 12 7 km along a road from a reference point rather than to a pair of coordinates or a landmark The road serves as the reference frame just as the earth serves as the reference frame for latitude and longitude Benefits EditLinear referencing can be used to define points along a linear feature with just a small amount of information such as the name of a road and the distance and bearing from a landmark along the road This information can be communicated concisely via plaintext For example State route 4 20 feet east of mile marker 187 Giving a latitude and longitude coordinate to a work crew is not meaningful unless the coordinate is plotted on a map Often work crews work in remote areas without wireless connectivity which makes on line digital maps not practical and the relatively higher effort of providing offline maps or printed maps is not as economical as simply stating locations as offsets or ranges of offsets along a linear feature Linear referencing systems can also be made to be both very precise and very accurate at a much lower cost than is needed to collect latitude and longitude coordinates with high accuracy especially when the goal is sub meter accuracy This is highly dependent upon the width of the linear feature its centerline and the visibility of the landmarks and markers that are used to define linear reference offsets Often roads are created by engineers using CAD tools that have no geospatial reference at all and LRS is the preferred method of defining data for linear features Limitations EditConsequently a major limitation of linear referencing is that specifying points that are not on a linear feature is troublesome and error prone though not entirely impossible Consider for example a ski lodge located 100 meters to the right of the road traveling north The linear referencing system can be extended by specifying a lateral offset but the absolute location i e coordinates of the lodge cannot be determined unless coordinates are specified for the road that process is prone to error particularly on curved roads Another major drawback of linear referencing is that a modification in the alignment of a road e g constructing a bypass around a town changes the measurements that reference all downstream points The system requires an extensive network of reference stations and constant maintenance In an era of mobile maps and GPS this maintenance overhead for linear referencing systems challenges its long term viability But see below for US Federal Highway Administration requirement that all State DOTs use LRS Nonetheless travel along a road is a linear experience and at the very least linear referencing will continue to have a conversational role Linear referencing systems are recognized by the US Federal government as a valuable tool for specifying right of way data and are now actually required for the States Therefore it is not likely to see LRS usage decline any time soon Applications EditARNOLD US Federal Requirements for Highways Edit The US Federal Highway Administration is pushing states to move closer to standardization of LRS data with the ARNOLD requirement To wit On August 7 2012 FHWA announced that the HPMS is expanding the requirement for StateDepartments of Transportation DOTs to submit their LRS to include all public roads This requirementwill be referred to as the All Road Network of Linear Referenced Data ARNOLD 1 The ARNOLD requirement sets the stage for systems that utilize both LRS and coordinates Both systems are useful in different contexts and while using latitude and longitude is becoming very popular due to the availability of practical and affordable devices for capturing and displaying global coordinate data the use of LRS has widely been adopted for planning engineering and maintenance Supported platforms EditLinear referencing is supported for example by several Geographic Information System software including Intergraph 2 3 GE Global Transmission Office 4 ArcGIS 5 GEOMAP GIS 6 GRASS GIS 7 PostGIS 8 QGIS 9 See also EditChainage also known as station references in construction surveying Exit number Geocoding Geographic coordinate system Length measurement Milestone Road map Zero mileReferences Edit All Road Network of Linear Referenced Data ARNOLD Reference Manual PDF Federal Highway Administration Retrieved 15 November 2016 Intergraph An LRS Model Supporting Event Location Stability and Temporal Data Management PDF a href Template Cite journal html title Template Cite journal cite journal a Cite journal requires journal help Intergraph White Paper An Automated Approach to Managing Components of a Linear Reference System Network and Event Data PDF a href Template Cite journal html title Template Cite journal cite journal a Cite journal requires journal help Benefits Smallworld Global Transmission Office a href Template Cite web html title Template Cite web cite web a Check url value help Esri 24 February 2009 ArcGIS 9 3 An overview of linear referencing Esri Retrieved 8 March 2011 Geomap Services 6 June 2011 GEOMAP GIS 2012 Solution for linear referencing and dynamic segmentation over Autodesk ESRI or MapInfo products Geomap Services Archived from the original on 25 April 2012 Retrieved 11 November 2011 Radim Blazek March 2005 Introducing the Linear Reference System in GRASS PDF International Journal of Geoinformatics 1 3 Retrieved 2007 05 01 PostGIS team 2010 PostGIS 1 5 2 Manual Retrieved 8 March 2011 LRS Plugin for QGIS Further reading EditNoronha Val Church Richard L 2002 Linear Referencing and Alternate Expressions of Location for Transportation PDF Santa Barbara California Vehicle Intelligence and Transportation Analysis Laboratory National Center for Geographic Information and Analysis archived from the original PDF on 20 July 2011 retrieved 8 March 2011 Curtin K Arifin R Nicoara G 2007 A Comprehensive Process for Linear Referencing PDF URISA Journal 19 2 41 50 archived from the original PDF on 2010 06 23 Retrieved from https en wikipedia org w index php title Linear referencing amp oldid 1111486446, wikipedia, wiki, book, books, library,

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