LateralOffsetExpressionType Linear Referencing Offset

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9.5.6 LateralOffsetExpressionType

complexType name=LateralOffsetExpressionType simpleContent extension base=double attribute name=uom type=gml:UomIdentifier attribute name=lateralOffsetReferent type=string attribute name=featureGeometry type=anyURI annotation documentation The featureGeometry attribute value should reference a Geometry object documentation appinfo gml:targetElement gmllr:AbstractGeometry gml:targetElement appinfo annotation attribute extension simpleContent complexType gmllr:LateralOffsetExpressionType implements ISO 19148 LRO_LateralOffsetExpression see ISODIS 19148, 6.4.6 and LRO_LateralOffsetReferent see ISODIS 19148, 6.4.7. gmllr:LateralOffsetExpressionType is used to describe the lateral offset for a linearly referenced location. The lateral offset distance is the measure of the lateral offset of the distance expression. This is the distance left or right of the lateral offset referent or left or right of the linear element being measured if no lateral offset referent is specified to the position being specified. A positive + value is measured in the direction specified by the positive lateral offset direction of the Linear Referencing Method. A value of 0 zero is to be interpreted as not having a lateral displacement from the lateral offset referent or the linear element being measured if no lateral offset referent is specified. The lateral offset distance is a double value extended with three attributes. The optional attribute gmllr:uom specifies the units of measure of the double value. It is of type gml:UomIdentifier. If none is provided, the uom value defaults to the offsetUnits value of the Linear Referencing Method. The optional attribute gmllr:lateralOffsetReferent indicates the base line for the lateral offset measure. gmllr:lateralOffsetReferent specifies the lateral offset referent as a character string. Having only a value of back of curb for example, allows a location to be specified as 5 feet behind the back of the curb. This aides in locating the position in the field without having to measure from the linear element. The value can be a conventional value, such as –L1 or RE from XSP see ISODIS 19148, C.5.2. If the curb is represented as a Feature with a spatial representation, the distance that the curb is from the linear element being measured is determinate and therefore the exact spatial position of the position expression can be calculated. Because the Feature can have multiple spatial representations, the gml:AbstractGeometry, rather than the Feature, is specified. 48 Copyright © 2012 Open Geospatial Consortium The optional attribute gmllr:featureGeometry is the geometry of a Feature. Though the type is anyURI, it is expected that the value will be a reference to an already defined gml:AbstractGeometry object. EXAMPLE The following Linear Referencing Method is Milepoint with lateral offsets measured in feet milepointWithLateralOffsetInFeet from Annex A. The distance expression: gmllr:distanceExpression gmllro:LateralOffsetDistanceExpression gml:id=DE002 gmllr:distanceAlong25gmllr:distanceAlong gmllro:lateralOffsetExpression lateralOffsetReferent=back of curb 5 gmllro:lateralOffsetExpression gmllro:LateralOffsetDistanceExpression gmllr:distanceExpression would specify a location that is 25 miles along the linear element then offset 5 feet behind the back of curb.

9.5.7 VerticalOffsetExpressionType