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w := width of Trackable h := height of Trackable calculated based on aspect ratio
3D Trackables tracked 3D models: origin: the origin of the model.
x, y and z axis are reused from the model Unit: As specified in the size property of the model or any implicit size detected in the model file
itself
Other Trackables: Trackables that do not fall into or cannot be mapped onto one of the above categories must specify
their local coordinate system on their own.
6.4.1.4 Advanced ARML: class RelativeTo
Inherits From ARAnchor. RelativeTo Anchors are defined relative to another ARAnchor except LineStrings, to the user or
relative to a Model. RelativeTo allows ARAnchors to be defined relative to other objects, regardless of where they are actually located. A Trackable, for example, defaults to a 0‐dimensional ARAnchor.
RelativeTo can be used to track the outline or any specific area in the Trackable without having to specify the Trackable again. The area can be specified using the local coordinate system of a
Trackable.
RelativeTo is specified using GMLGeometryElements. The coordinate system is calculated according to the rules set forth in Local Coordinate Systems of GMLGeometryElements, based on the
underlying ARAnchor or Model in which case the models xz plane serves as the surface plane for coordinate system calculations.
While it is technically possible to define RelativeTo anchors relative to another RelativeTo anchor, usage of this construct is discouraged due to complex local coordinate system handling. It is advised
to always base a RelativeTo‐Anchor directly on a non‐RelativeTo ARAnchor, a Model or the user.
Copyright © 2015 Open Geospatial Consortium 28
Properties: Name
Description Type
Multiplicity
ref The ARAnchor or Model the RelativeTo Anchor is
referencing string
1
GMLGeometry The geometry describing the RelativeTo ARAnchor
GMLGeometryElement 1
ref Specifies the URI to the object the Anchor is referencing. Either another ARAnchor except
LineStrings or Model, or user is allowed as reference. If an ARAnchor is specified as ref, the ARAnchors local coordinate system is used to calculate the relative location based on the
GMLGeometryElement of the RelativeTo Anchor. If a Model is used, the engineering coordinate system of the Model is used as coordinate system for the calculation of the relative location.
If user is provided as reference, the current location of the user is considered a Point‐Anchor with its local coordinate system set accordingly.
GMLGeometry The GMLGeometry describes the location relative to the object specified in ref. Thus, the resulting
RelativeTo‐Anchor can either be a gml:Point, gml:LineString or gml:Polygon, and the coordinates are given with respect to the underlying coordinate system of the ARAnchor or the coordinate system of
the Model. srsName and srsDimension for the GMLGeometryElement are ignored, srsDimension is implicitly set
to 3. The local coordinate system of the underlying ARAnchor or Model will be used.
Requirement
http:www.opengis.netspecarml2.0reqcoreRelativeToGMLGeometry_properties The GMLGeometry properties srsName and srsDimension are ignored when used within RelativeTo
anchors. srsDimension is implicitly set to 3.
6.4.2 class ScreenAnchor
