Part 210: Relative Spatial Location (RSL)
| Document number | OPC 10000-210 |
|---|---|
| IEC designation | IEC 62541-210 - publication not confirmed |
| Colloquially | Part 210 |
| Group | Domain |
Part 210 defines how to express where something is relative to something else: spatial objects, the attach points that connect them, and the position and orientation between them. It is the geometric vocabulary for describing a cell, a line or a mobile machine inside an address space. Namespace http://opcfoundation.org/UA/RSL/.
What it defines
A spatial object is a thing with a position and orientation that other things can be located against. Attach points are the named places on it where relationships are anchored, so a location is expressed as a transformation between two identified points rather than as a bare triple of numbers. That indirection is the whole design: it means a relationship survives one of the objects moving, and it means a client reading a position knows what the position is relative to without out-of-band knowledge.
Why relative and not absolute
Most industrial geometry is relative. A gripper is positioned against a flange, the flange against a robot base, the base against a cell datum, the cell against the building. Modelling each link separately gives a chain a client can walk and a tool can recompute when one element is re-sited, and it avoids the trap of storing every coordinate against one global origin that nobody surveys accurately. Absolute geographic position is a separate concern, handled by Part 211, which builds on this part rather than replacing it.
Status and adoption
The released nodeset for this namespace is at version 1.00.1 - a first major version, and one of the newest additions to the standard. Its conformance units are named in the released material, with the spatial-object attach-point unit being the core one, and those names are the right thing to cite in a requirement. Expect early-adopter conditions: few servers publish this namespace today, and tool support for visualising it is thin.
The conventions you have to pin
A geometric model is only as good as the conventions around it. Rotation representation, axis ordering, handedness, angle units and length units all have to agree between the publisher and the consumer, and the model carries engineering units on its values for exactly that reason. Read them rather than assuming millimetres and degrees. On a project spanning a robot vendor, a machine vendor and a simulation tool, agreeing these in writing before integration is cheaper than discovering the mismatch from a collision.
What it defines
| Concept | What it is |
|---|---|
| Namespace URI | http://opcfoundation.org/UA/RSL/ - the identifier to check in NamespaceArray to find out whether a server implements the model at all. |
| Model version | The released nodeset is at version 1.00.1. A first major version, so pin it in your design and expect movement. |
| Spatial object | A thing with a position and orientation that other things can be located against. The unit of the model, and the anchor for attach points. |
| Attach point | A named place on a spatial object where a relationship is anchored, so a location is a transformation between two identified points rather than an unqualified coordinate. |
| Relative location chain | Locations compose - gripper to flange, flange to base, base to cell datum - giving a walkable chain that survives one element being re-sited. |
| SpatialObject AttachPoints conformance unit | The core named conformance unit of the model. Cite it in a requirement rather than citing the part in the abstract. |
| Engineering units on geometry | Length and angle values carry unit metadata. Read it rather than assuming millimetres and degrees, particularly across vendors. |
| Relationship to global positioning | Part 211 builds on this part to add absolute geographic position. Relative geometry is the foundation, not an alternative. |
Do you need to read it?
Robotics and mobile-equipment integrators, anyone building a digital twin or a simulation that has to consume real machine geometry, and modellers who need to express layout rather than just process values. For a conventional data-collection project this part is background reading.
Traps that trace back to this part
- A position without its reference is not a position. The value is only meaningful with the attach points it relates, so a client that reads coordinates and discards the relationship has captured numbers, not geometry. Store the chain, or store the resolved transformation together with what it was resolved against.
- Pin the geometric conventions in writing. Rotation representation, axis order, handedness and units have to match between publisher and consumer, and nothing in a successful read tells you they do. Read the engineering units on the values and agree the rest with every vendor in the chain before integration.
- This is a first-major-version model with thin deployment. Confirm the namespace is actually published by the specific device and firmware you are buying, and confirm your tooling can consume it, rather than inferring availability from the standard existing.
Last verified 7 September 2026 against OPC UA 1.05.07. The specification parts themselves are published by the OPC Foundation. OPC UA Connect is an educational resource and is not affiliated with the OPC Foundation.