Linear referencing

The location (road network connection) is calculated by "projecting" the road object's geometry onto the nearest relevant road network at road route level. The prerequisite is therefore that the road objects have at least one geometry property.

NOTE
Some road object types do not have their own geometry. An example of this could be Speed limit (105). Here, anchoring must be added to the linear referencing to get the correct result. The Data catalogue will help you with the necessary management parameters.

It is important to note that road object types that have a single point linear referencing cannot be geolocated if they been registered with both a start and an end point linear reference. Therefore, the service will ignore end point linear reference in such cases. For best results, do not use anchoring for road object types with own geometry.

The location endpoint takes into account factors such as:

• The lifetime of the road object (limits the applicable road network for positioning)
• Whether the road object type allows linear referencing on connecting road links
• Minimum length for segment linear referencing
• Whether the road object type requires the location to be within the location of the parent object

Calculated segment linear referencing can consist of several linear referencing elements (several road link sequences). In such cases, it describes a continuous route along one and the same road. A road in this context is the combination of road category, road phase and road number.

The response from the endpoint, if a location could be calculated, is guaranteed to be valid for the road object in question at the time it was delivered. However, the road network can change over time and invalidate a previously valid linear referencing.

Received linear referencing data should therefore be used in a change set within a reasonable time.

Validation

Road objects sent to the linear referencing endpoint undergo a small validation sequence to ensure that sufficient correct information has been delivered for linear referencing to be carried out. The validation checks limitations against the Data catalogue and context within the linear referencing request.

Among other things, the validation checks that:

• The road object type is known in the Data catalogue.
• The property types are known in the Data catalogue and allowed for the relevant road object type.
• The road object type requires point or segment linear referencing.
• The road object type has at least one geometry property.
• The road object has set at least one geometry property.
• Geometry properties have a valid value.

If one or more irregularities are uncovered, the response will include a description of these. In addition to the notification codes that are common with change sets, the following codes may occur:

Notification code	Definition
UGYLDIG_GEOMETRI	The road object has no valid geometry properties.
STEDFESTING_MISLYKTES	Valid road network association for the road object was not found with the specified parameters.
UGYLDIG_VEGOBJEKTTYPE	The road object does not require point or segment linear referencing.
RUTE_ER_MINDRE_ENN_1_METER	Submitted parameters gave a route of less than 1 metre.
VEGOBJEKTET_KAN_IKKE_STEDFESTES_PÅ_KONNEKTERINGSLENKER	The road object type cannot be located on connection links.
UGYLDIG_ANKERPUNKT	A single point linear reference cannot be calculated with anchoring that has two anchor points.
UGYLDIG_MOR	Cannot find the parent object or the child object cannot be associated with the specified parent object.
MOROBJEKT_MANGLER_STEDFESTING	Cannot linear reference the child object when linear referencing the parent object failed.
MOR_DEKKER_IKKE_DATTEROBJEKT	The child object could not be linear referencing within the parent object.
STEDFESTING_FLYTTET	The child object was moved to the nearest endpoint of the parent object.

Geometry properties

Some road object types allow multiple geometry properties. For the most precise location, it is recommended that as many of the geometry properties as possible are included in the road objects, including road object types that are to have a single point linear reference.

The geometry property used to project to a single point linear reference is selected according to the following priority:

1. Item
2. Curve (using the centroid)
3. Surface (using the centroid)

The geometry property used to project to a segment linear referencing is selected according to the following priority:

1. Curve
2. Surface
3. Item

Parent and child relationships

If parent and child objects are delivered in the same request and the association between them is described, the location of the child object will take into account whether it is a road object type that requires the location to be within the location of the parent object.

As a result, the service will ensure that the order of the road objects you want to linear reference is sorted by parent - child association. If the child refers to the parent who is also to be linear referenced in the same request, this will take place before the child, which means that the child can adopt the location of the parent where this is relevant.

In cases where a child is associated with an existing parent, the service will retrieve the necessary information about the parent in order to linear reference the child in accordance with the management parameters in the Data catalogue.