Difference between revisions of "Coordinate positioning"

From wiki.railtopomodel.org
Jump to navigation Jump to search
m
(Review and adaption of section about coordinate reference systems)
Line 1: Line 1:
{{Overview|text=Lorem ipsum...}}<br />
+
{{Overview|text=This chapter introduces the concept of locating railway infrastructure elements by using coordinate reference systems.}}<br />
  
Systems of this kind are based on the concept of Geometrical coordinates.<br />
+
Besides the intrinsic and the linear track-referenced coordinate system the RailTopoModel also allows to locate railway infrastructure elements using geodetic and geometric coordinate systems. The most known example in this case is the World Geodetic System WGS84.<br />
 
<gallery>
 
<gallery>
 
File:GeometricCoordinates.png|Geometric Coordinates (© RFF/SNCF Réseau)
 
File:GeometricCoordinates.png|Geometric Coordinates (© RFF/SNCF Réseau)
 
</gallery>
 
</gallery>
  
It could either be a projected X, Y, Z coordinate, a λ, ϕ, h geodetic coordinate or even an X, Y(, Z) schematic plan coordinate.<br />
+
= General =
It could be read as “at coordinate X, Y, Z in the system [EPSG:xxxxx] [01/06/2014]4” [4: The exact content of the definition string of the geometric system is not yet definitve] <br />
+
A geometric coordinate system can either be a projected X, Y, Z coordinate, a λ, ϕ, h geodetic coordinate or even an X, Y(, Z) schematic plan coordinate.<br />
 +
It could be read as "at coordinate X, Y, Z in the system [EPSG:xxxxx] [01/06/2014]4" [4: The exact content of the definition string of the geometric system is not yet final] <br />
 
The model integrates a link between the linear positioning system and the intrinsic positioning system. It supports the "conversion" of an element position associated with a number between 0 and 1 to a kilometric point on its reference system.<br />
 
The model integrates a link between the linear positioning system and the intrinsic positioning system. It supports the "conversion" of an element position associated with a number between 0 and 1 to a kilometric point on its reference system.<br />
  
Line 14: Line 15:
 
</gallery>
 
</gallery>
  
'''Comment:'''<br />
+
= EPSG Code =
An example of an aggregation mechanism is depicted in Annex B.
+
As there are a number of different coordinate reference systems with different parameter sets available, it is important to identify the coordinate system without ambiguity. The International Association of Oil & Gas Producers set up the EPSG Geodetic Parameter Registry, which provides a unique code for every coordinate system. The websites http://spatialreference.org/ and http://www.epsg-registry.org/ can be used to obtain an overview about different coordinate systems by their EPSG code.
The classes, used to define the location and positioning systems, are:
+
 
* '''PositioningSystem''': This class defines the general concept of a Reference System.
+
== Examples ==
* '''LinearPositioningSystem''': This class defines a Linear Referencing System. It defines a starting and an ending coordinate.
+
* EPSG code for World Geodetic System WGS84: urn:ogc:def:crs:EPSG::4326
* '''LinearAnchorPoints''': this class describes the reference points in the linear reference system (Milestones, anomaly points…) and their characteristics.
+
* EPSG code for ETRS89 / ETRS-TM32: urn:ogc:def:crs:EPSG::3044
 +
* EPSG code for the height coordinate system DHHN92: urn:ogc:def:crs:EPSG::5783
 +
 
 +
= Relevant classes in the RTM =
 +
The classes, used to define the location and positioning systems and their coordinates, are:
 +
* '''PositioningSystem''': This class defines the general concept of a Coordinate Reference System used for positioning.
 +
* '''LinearPositioningSystem''': This class defines a Linear Referencing System. It defines a start and an end coordinate.
 +
* '''LinearAnchorPoints''': this class describes the reference points within the linear reference system (Milestones, anomaly points...) and their characteristics.
 
* '''LinearCoordinate''': This class defines the localization expressed in a Linear Reference System (LRS).
 
* '''LinearCoordinate''': This class defines the localization expressed in a Linear Reference System (LRS).
* '''GeometricPositioningSystem''': This class defines a Geometrical Reference System, so it allows to localise a resource with his geometrical coordinates (x, y, z or λ, ϕ, h).
+
* '''GeometricPositioningSystem''': This class defines a Geometrical Reference System, so it allows to locate a resource with its geometrical coordinates (x, y, z or λ, ϕ, h). The class provides the parameter ''crsDefinition'' to define the Coordinate Reference System. This parameter shall be used to name the EPSG code and thus define all the relevant parameters of the coordinate system.
 
* '''GeometricCoordinate''': This class defines the localization expressed in a geometrical (or geographical) Reference System, so it defines the coordinates (x, y, z or λ, ϕ, h).
 
* '''GeometricCoordinate''': This class defines the localization expressed in a geometrical (or geographical) Reference System, so it defines the coordinates (x, y, z or λ, ϕ, h).
* '''PositioningSystemCoordinate''': This class represent a coordinate in either a geometric or linear reference system.
+
* '''PositioningSystemCoordinate''': This class represents a coordinate in either a geometric or linear reference system.
* '''IntrinsicCoordinate''': This class allows associating an intrinsic coordinate to another coordinate, either geographic or linear.
+
* '''IntrinsicCoordinate''': This class allows associating an intrinsic coordinate coming from the topology network to another coordinate, either geographic or linear.
 
* '''AssociatedPositioningSystem''': This class allows to group couples of coordinates to define the translation parameters between an external (geometric or linear) coordinate system and the element’s intrinsic coordinate system.
 
* '''AssociatedPositioningSystem''': This class allows to group couples of coordinates to define the translation parameters between an external (geometric or linear) coordinate system and the element’s intrinsic coordinate system.
  
Line 31: Line 39:
 
|-
 
|-
 
| '''What you should have learned'''<br />
 
| '''What you should have learned'''<br />
Lorem ipsum...
+
* Coordinate reference systems are (besides intrinsic and linear referencing) the third option to define positions in the RailTopoModel.
*  
+
* All geodetic coordinate reference systems can be defined by a unique identifier: the EPSG code.
* Bulleted list item
+
* Coordinate reference systems can be also used to define schematic coordinates as they are used in terms of screen coordinates.
 
|}
 
|}
  

Revision as of 13:18, 6 June 2016

Overview
This chapter introduces the concept of locating railway infrastructure elements by using coordinate reference systems.


Besides the intrinsic and the linear track-referenced coordinate system the RailTopoModel also allows to locate railway infrastructure elements using geodetic and geometric coordinate systems. The most known example in this case is the World Geodetic System WGS84.

General

A geometric coordinate system can either be a projected X, Y, Z coordinate, a λ, ϕ, h geodetic coordinate or even an X, Y(, Z) schematic plan coordinate.
It could be read as "at coordinate X, Y, Z in the system [EPSG:xxxxx] [01/06/2014]4" [4: The exact content of the definition string of the geometric system is not yet final]
The model integrates a link between the linear positioning system and the intrinsic positioning system. It supports the "conversion" of an element position associated with a number between 0 and 1 to a kilometric point on its reference system.

EPSG Code

As there are a number of different coordinate reference systems with different parameter sets available, it is important to identify the coordinate system without ambiguity. The International Association of Oil & Gas Producers set up the EPSG Geodetic Parameter Registry, which provides a unique code for every coordinate system. The websites http://spatialreference.org/ and http://www.epsg-registry.org/ can be used to obtain an overview about different coordinate systems by their EPSG code.

Examples

Relevant classes in the RTM

The classes, used to define the location and positioning systems and their coordinates, are:

  • PositioningSystem: This class defines the general concept of a Coordinate Reference System used for positioning.
  • LinearPositioningSystem: This class defines a Linear Referencing System. It defines a start and an end coordinate.
  • LinearAnchorPoints: this class describes the reference points within the linear reference system (Milestones, anomaly points...) and their characteristics.
  • LinearCoordinate: This class defines the localization expressed in a Linear Reference System (LRS).
  • GeometricPositioningSystem: This class defines a Geometrical Reference System, so it allows to locate a resource with its geometrical coordinates (x, y, z or λ, ϕ, h). The class provides the parameter crsDefinition to define the Coordinate Reference System. This parameter shall be used to name the EPSG code and thus define all the relevant parameters of the coordinate system.
  • GeometricCoordinate: This class defines the localization expressed in a geometrical (or geographical) Reference System, so it defines the coordinates (x, y, z or λ, ϕ, h).
  • PositioningSystemCoordinate: This class represents a coordinate in either a geometric or linear reference system.
  • IntrinsicCoordinate: This class allows associating an intrinsic coordinate coming from the topology network to another coordinate, either geographic or linear.
  • AssociatedPositioningSystem: This class allows to group couples of coordinates to define the translation parameters between an external (geometric or linear) coordinate system and the element’s intrinsic coordinate system.


What you should have learned
  • Coordinate reference systems are (besides intrinsic and linear referencing) the third option to define positions in the RailTopoModel.
  • All geodetic coordinate reference systems can be defined by a unique identifier: the EPSG code.
  • Coordinate reference systems can be also used to define schematic coordinates as they are used in terms of screen coordinates.


Back To Previous Chapter Next Chapter
Positioning - Track-referred positioning