IFC 4.3.x development

8.18.3.5 IfcMapConversion

Change log

IFC4

added

IFC4X3_RC3

additionsattributesScaleY
additionsattributesScaleZ

8.18.3.5.1 Semantic definitions at the entity

The map conversion deals with transforming the local engineering coordinate system, often called world coordinate system, into the coordinate reference system of the underlying map.

NOTE  The IfcMapConversion does not handle the projection of a map from the geodetic coordinate reference system.

The map conversion allows to convert the local origin of the local engineering coordinate system to its place within a map (easting, northing, orthogonal height) and to rotate the x-axis of the local engineering coordinate system within the horizontal (easting/westing) plane of the map.

NOTE  The z axis of the local engineering coordinate system is always parallel to the z axis of the map coordinate system.

The scale factor can be used when the length unit for the 3 axes of the map coordinate system are not identical with the length unit established for this project (see IfcProject.UnitsInContext), if omitted, the scale factor 1.0 is assumed.

HISTORY  New entity in IFC4

8.18.3.5.1 Attributes

#Attribute Type Description
IfcCoordinateOperation
1SourceCRS IfcCoordinateReferenceSystemSelectSource coordinate reference system for the operation.
2TargetCRS IfcCoordinateReferenceSystem Target coordinate reference system for the operation.
IfcMapConversion
3Eastings IfcLengthMeasure Specifies the location along the easting of the coordinate system of the target map coordinate reference system.

> NOTE  for right-handed Cartesian coordinate systems this would establish the location along the x axis.
4Northings IfcLengthMeasure Specifies the location along the northing of the coordinate system of the target map coordinate reference system.

> NOTE  for right-handed Cartesian coordinate systems this would establish the location along the y axis
5OrthogonalHeightIfcLengthMeasure Orthogonal height relativ to the vertical datum specified.

> NOTE  for right-handed Cartesian coordinate systems this would establish the location along the z axis
6XAxisAbscissa OPTIONAL IfcReal Specifies the value along the easing axis of the end point of a vector indicating the position of the local x axis of the engineering coordinate reference system.

> NOTE 1 for right-handed Cartesian coordinate systems this would establish the location along the x axis

> NOTE 2 together with the XAxisOrdinate it provides the direction of the local x axis within the horizontal plane of the map coordinate system
7XAxisOrdinate OPTIONAL IfcReal Specifies the value along the northing axis of the end point of a vector indicating the position of the local x axis of the engineering coordinate reference system.

> NOTE 1 for right-handed Cartesian coordinate systems this would establish the location along the y axis

>

XAxisAbscissa it provides the direction of the local x axis within the horizontal plane of the map coordinate system.
8Scale OPTIONAL IfcReal Scale to be used, when the units of the CRS are not identical to the units of the engineering coordinate system. If omited, the value of 1.0 is assumed.
9ScaleY OPTIONAL IfcReal Scale Y by which the length measures in local engineering CS have to be multiplied to get map coordinates
10ScaleZ OPTIONAL IfcReal Scale Z by which the length measures in local engineering CS have to be multiplied to get map coordinates

8.18.3.5.2 Entity inheritance

dot_inheritance IfcMapConversion IfcMapConversion IfcCoordinateOperation IfcCoordinateOperation IfcMapConversion->IfcCoordinateOperation

8.18.3.5.3 Formal representations

ENTITY IfcMapConversion
 SUBTYPE OF (IfcCoordinateOperation);
	Eastings : IfcLengthMeasure;
	Northings : IfcLengthMeasure;
	OrthogonalHeight : IfcLengthMeasure;
	XAxisAbscissa : OPTIONAL IfcReal;
	XAxisOrdinate : OPTIONAL IfcReal;
	Scale : OPTIONAL IfcReal;
	ScaleY : OPTIONAL IfcReal;
	ScaleZ : OPTIONAL IfcReal;
END_ENTITY;