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
complexType name=VerticalOffsetExpressionType simpleContent
extension base=double attribute name=uom type=gml:UomIdentifier
attribute name=verticalOffsetReferent type=string attribute name=featureGeometry type=anyURI
annotation appinfo
gml:targetElement gmllr:AbstractGeometry
gml:targetElement appinfo
annotation attribute
extension simpleContent
complexType gmllr:VerticalOffsetExpressionType implements ISO 19148 LRO_VerticalOffsetExpression see
ISODIS 19148, 6.4.8 and LRO_VerticalOffsetReferent see ISODIS 19148, 6.4.9.
gmllr:VerticalOffsetExpressionType is used to describe the vertical offset for a linearly referenced location.
The vertical offset distance is the measure of the vertical offset of the distance expression. This is the distance above or below the vertical offset referent or above or below the linear element being measured if no
vertical offset referent is specified to the position being specified. A positive + value is measured in the direction specified by the positive vertical offset direction of the Linear Referencing Method. A value of 0
zero is to be interpreted as not having a vertical displacement from the vertical offset referent or the linear element being measured if no vertical offset referent is specified. The vertical 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.
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The optional attribute gmllr:verticalOffsetReferent indicates the base line for the vertical offset measure.
gmllr:verticalOffsetReferent specifies the vertical offset referent as a character string. Having only a value of existing ground at lateral offset for example, allows a location to be specified as 5 feet above the
existing ground at the lateral offset for example, back of the curb. This aides in locating the position in the field without having to measure from the linear element.
If the curb is represented as a Feature with a spatial representation, the height of the curb 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:Geometry, rather than the Feature, is specified.
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.
9.5.8 LateralOffsetDirectionType
