12.12 Junction CRG surface

In order to describe complex elevations within a junction on a very detailed level, a surface description for junctions can be specified. This is accomplished by describing the junction surface in correspondence with the descriptions used in ASAM OpenCRG. For junctions that are not flat but without a very detailed surface description, the <elevationGrid> should be used.

The CRG data may be applied to a given junction in different modes similar to a road, using the junction reference line specified by the <planview> element.

Table 81. Modes of connecting ASAM OpenCRG to ASAM OpenDRIVE
Mode	ASAM OpenCRG reference line	Total height	Typical use case
attached	discarded	ASAM OpenDRIVE junction height plus ASAM OpenCRG height	Relative road height to road surface (including interpolated elevation grid and lane height)
attached0	discarded	ASAM OpenCRG height only	Absolute height measurement
genuine	shifted and rotated so beginning of ASAM OpenCRG reference line matches position on junction reference line given in ASAM OpenDRIVE	ASAM OpenCRG height only	Combining complete ASAM OpenCRG tracks (for example, junction surface measurement) with ASAM OpenDRIVE data
global	taken unmodified	ASAM OpenCRG height only	On junctions

For a detailed explanation of the different modes, see Section 10.6, "Road CRG surface". Instead of a road reference line use the junction reference line to place CRG data on the junction surface.

Elements in UML model

<surface> element

In ASAM OpenDRIVE, surfaces in a junction are represented by the <surface> element within the <junction> element and use the same information as the <road> element.

UML class: t_road_surface
XML tag:   <surface> (Multiplicity: 0..1)

Contains a series of elements describing a surface.

<CRG> element

In ASAM OpenDRIVE, ASAM OpenCRG data of road surfaces is represented by the <CRG> element within the <surface> element.

UML class: t_road_surface_CRG
XML tag:   <CRG> (Multiplicity: 0..*)

Links road surface data defined according to ASAM OpenCRG format.

Table 82. Attributes of the <CRG> element
Name	Type	Use	Unit	Description
`file`	string	required		Name of the file containing the CRG data
`hOffset`	double	optional	rad	Heading offset between CRG center line and reference line of the road (only allowed for mode genuine, default = 0.0).
`mode`	e_road_surface_CRG_mode	required		Attachment mode for the surface data, see specification.
`orientation`	e_direction	required		Orientation of the CRG data set relative to the parent `<road>` element. Only allowed for mode attached and attached0.
`purpose`	e_road_surface_CRG_purpose	optional		Physical purpose of the data contained in the CRG file; if the attribute is missing, data will be interpreted as elevation data.
`sEnd`	t_grEqZero	required	m	End of the application of CRG (s-coordinate)
`sOffset`	double	optional	m	s-offset between CRG center line and reference line of the road (default = 0.0)
`sStart`	t_grEqZero	required	m	Start of the application of CRG data (s-coordinate)
`tOffset`	double	optional	m	t-offset between CRG center line and reference line of the road (default = 0.0)
`zOffset`	double	optional	m	z-offset between CRG center line and reference line of the road (default = 0.0). Only allowed for purpose elevation.
`zScale`	double	optional		z-scale factor for the surface description (default = 1.0). Only allowed for purpose elevation.

Rules

The following rules apply to junction CRG surfaces:

Junction CRG surfaces shall use the junction reference line.
When a <junction> element contains a <surface> element, the <surface> element supersedes all elevation data for connecting roads.

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