- Watch out
- What it costs
- Experienced readers
- Remember
- In BIMpedia
A building sits on one site with one owner. A railway, a road or a pipeline runs for kilometres through fields, towns, rivers and protected land, past and under networks that belong to other companies. Most of what decides where it can go is managed in GIS by somebody else.
| Layer | Who usually holds it | Why the design needs it |
|---|---|---|
| Land parcels and ownership | Land registry, the client's land team | Who to negotiate with; where you may work |
| Consents and planning limits | Authorities | Where the scheme is allowed to go |
| Environmental constraints | Environmental agencies | Protected habitats, flood zones, heritage |
| Existing utilities | Utility owners | What must be avoided, diverted or protected |
| Terrain and imagery | Survey, mapping agencies | Ground levels, context |
Where BIM and GIS divide the work
| GIS | BIM |
|---|---|
| The whole corridor, at 1:1,000 to 1:50,000 | Bridges, stations, culverts, buildings, at 1:50 to 1:500 |
| Layers of features with attributes | Elements with geometry and properties |
| Real-world coordinates, always | A project origin linked to them |
| Many owners' data, of mixed quality | The design team's own models |
The two meet in three places: the alignment (the line everything is measured along), the coordinate reference system (shared by both) and identifiers (so a structure in the model is the same thing as a feature on the map).
The design team downloads the environmental constraints once, at the start. Fourteen months later a new protected site is designated across the route. Nobody re-checks the layer, and the design reaches the consent submission crossing it.
The information standard lists every corridor layer with its source, date and owner, and a monthly check for updates. The new designation appears in the next check; the alignment is moved while it is still a line on a plan.
You coordinate the design of a new 12 km water main between two towns. List six GIS layers the design team needs, and for each say who is likely to hold it and one thing you must know about it before using it.
Key takeaways
- Linear projects cross land, networks and constraints that are managed in GIS by many owners.
- GIS holds the corridor (land, consents, environment, utilities); BIM holds the structures and systems built in it.
- Each GIS layer needs a source, a date, a coordinate system and a stated accuracy.
- IFC 4.3 brings alignments and infrastructure into open BIM, so the two can meet on one reference.