When anchoring a wire at a structure, the wire heights are always measured vertically from the high rail level (HRL) of the structure. This ensures that a consistent datum-point is used regardless of the location of the anchored wire - i.e. the same datum-point is used whether the wire is anchored to a mast or along a gantry.
As anchored wires aren't registered to a specific track - they're attached to a mast or along a gantry - it isn't possible to define the heights from an individual track.
Using the consistent datum-point of HRL provides the following benefits:
- There's no ambiguity or confusion on where the wire height is measured from
- Equipment heights for multiple anchored wires will be predictable, regardless of where on the structure they’re attached to
Please note: Updating the tracks associated with the structure may update the HRL - in this case the wire heights will be measured from the new HRL datum-point. So for example, reassociating the tracks with a structure where the tracks have been raised by 50mm will mean that anchoring equipment will also be raised by 50mm to account for the change in datum-point.
The picture below shows how using a consistent datum-point for anchored wires means that the equipment will align regardless of which mast it is attached to.