Building Information Modelling is changing the way the engineering, architecture and construction industry is operating. The availability of BIM models provide a very rich source of data but due to the use of specific data models and standards integrating this data with GIS introduces challenges. In this presentation we introduce BIM and the major differences with GIS, we give an overview of the standards in the BIM end Geo domain, introduce the major open source BIM tools and demonstrate the integration of BIM models in a GIS environment.

1. www.gim.be
Open BIM:
bridging the gap
between BIM
and GIS
Brussels, 24 October 2019
Stijn Goedertier

2. BIMy – BIM in the city
• ITEA research project: 2018 –
2021
• Belgian and Turkish partners
• open platform
• for sharing, storing and
filtering BIMs among different
BIM owners/users
• integrating and visualizing
them in their built and natural
environment
Open BIM: open-source solutions for BIM-GIS integration 3

3. BIM versus GIS
GIS
• lower scale
• geospatial CRS
• surfacic (2D)
• Topological relations
• Surveying as source
• Standards: GML (OGC), …
• variety: vector data, coverages,
point clouds, orthoimagery,
elevation models, …BIM
• higher scale
• engineering CRS
• volumetric (3D)
• element composition
• human design as source
• standards: DWG, IFC
(BuildingSMART)
• vector data (documents)
Source: BuildingSmart, Thomas Liebich
Open BIM: open-source solutions for BIM-GIS integration 4

4. Standards – Industry Foundation
Classes (IFC)
IFC is an open, vendor-neutral data
standard
Standardised by the buildingSMART
consortium, also legal ISO standard
(ISO 16739)
IFC data model defined using
EXPRESS modelling language (ISO
10303)
IFC data in STEP or STEP-XML
format (ISO 10303)
IFC defines types like IfcSpace,
IfcBuildingStorey, IfcWall, etc.
Open BIM: open-source solutions for BIM-GIS integration 5
Source: buildingSMART

5. Standards – Industry Foundation
Classes (IFC)
IFC adopts the STEP geometry and
topology model from ISO 10303-42,
using
 Constructive Solid Geometry
(e.g. union operations)
 Boundary Representation (e.g.
extrusion operations)
See also: FME CSGBuilder,
CSGEvaluator
Open BIM: open-source solutions for BIM-GIS integration 6
Constructive Solid Geometry (Source: wikipedia)

6. Standards – CityGML
• CityGML is a data model for virtual 3D
city models
• GML 3 application schema
• OGC Standard
• Application Domain Extensions (ADEs)
• CityGML 3.0 in the making (with
CityJSON encoding)
BIM-naar-GIS dataverwerking - FLAGIS - 11 December 2018 7

7. Standards – CityGML
GML defines a 3D geometry model
used in application profiles like
CityGML, InfraGML, etc.
3D geometry types in GML:
 Surface: a planar area in 3D space
 Solid: a volume closed in 3D
space, defined by connected
surfaces
Open BIM: open-source solutions for BIM-GIS integration 8
Source: FME SurfaceBuilder Source: FME TinGenerator
source:
http://en.wiki.quality.sig3d.o
rg

8. CityGML 3.0 – Geometry model
Open BIM: open-source solutions for BIM-GIS integration 9
class Core - Geometry and LoD concept
«type»
Geometry root::GM_Object
GM_Primitive
«type»
Geometric primitive::
GM_Point
AbstractCityObject
«FeatureType»
AbstractSpace
AbstractCityObject
«FeatureType»
AbstractThematicSurface
«FeatureType»
AbstractPhysicalSpace
«FeatureType»
AbstractOccupiedSpace
GM_Primitive
«type»
Geometric primitive::
GM_Solid
GM_MultiPrimitive
«type»
Geometric aggregates::
GM_MultiSurface
GM_MultiPrimitive
«type»
Geometric aggregates::
GM_MultiCurve
Core module -
Geometry and LoD concept
«FeatureType»
ImplicitGeometry
«Property»
+ libraryObject: URI [0..1]
+ mimeType: Code [0..1]
+ transformationMatrix: TransformationMatrix4x4 [0..1]
*
+lod1MultiSurface
«Property»
0..1
*
+lod3TerrainIntersectionCurve
«Property»
0..1
*
+lod3MultiSurface
«Property»
0..1
*
+lod2TerrainIntersectionCurve
«Property»
0..1
*
+referencePoint
«Property» 1
*
+lod2MultiSurface
«Property»
0..1
*
+lod3Solid
«Property»
0..1
*
+lod0MultiSurface
«Property»
0..1
*
+lod3MultiCurve
«Property»
0..1
+bounds
«Property»*
+boundary
«Property» *
*
+lod3ImplicitRepresentation
«Property»
0..1
*
+relativeGMLGeometry
«Property»
0..1
*
+lod1ImplicitRepresentation
«Property»0..1
*
+lod1TerrainIntersectionCurve
«Property»
0..1
*
+lod2ImplicitRepresentation
«Property»
0..1
*
+lod1Solid
«Property»
0..1
*
+lod2MultiCurve
«Property»
0..1
*
+lod0Point
«Property»0..1
*
+lod3MultiSurface
«Property»
0..1
*
+lod2Solid
«Property»
0..1
*
+lod2MultiSurface
«Property»
0..1
*
+lod0MultiCurve
«Property»
0..1

9. Open issues
• Tool support for IFC
• Information delivery specifications for georeferencing
BIMs
• Inevitable information loss when converting IFC to
CityGML
Open BIM: open-source solutions for BIM-GIS integration 10

10. Storage – Postgres/PostGIS
3D geometries in PostGIS: POINT,
LINE, POLYGON, TIN, POLYHEDRAL
surface
3D functions in PostGIS:
ST_3DClosestPoint, ST_3DDistance,
ST_3DDWithin, ST_3DDFullyWithin,
ST_3DIntersects, ST_3DLongestLine,
ST_3DMaxDistance,
ST_3DShortestLine
3DCityDB: CityGML data model for
PostGIS, 3DCityDB importer-
exporter
Open BIM: open-source solutions for BIM-GIS integration 11

11. Storage – BIMServer
IFC data store: (IFC2x3, IFC4) based
on BerkleyDB
Stores: native geometry ánd
triangular meshes
ReST API
Plugins for visualisation,
management, model merging, model
checking, etc: BIMviews, BIMSurfer,
etc.…
http://bimserver.org/
Open BIM: open-source solutions for BIM-GIS integration 12

12. Storage – GeoRocket
GeoRocket is a "high-performance
data store for geospatial vector
data".
GeoRocket splits any XML or
GeoJSON file up in chunks, indexes
them using ElasticSearch, and is
capable of responding to (spatial)
queries by merging those chunks
back together.
https://georocket.io/
Open BIM: open-source solutions for BIM-GIS integration 13

13. Transformation – IfcOpenShell
Geometry engine: uses Open
CASCADE to convert IFC B-Rep
geometry into triangulated meshes.
Plug-ins for Blender, BIMserver, 3DS
Max, etc.
Open BIM: open-source solutions for BIM-GIS integration 14

14. Transformation – CGAL
Geometry types: point, line, 3D
polyhedral surfaces, TINs
Operations:
• Afine transformations
• 3D mesh generation,
• mesh approximation
(simplification)
• …
Qt5 visualisation
Open BIM: open-source solutions for BIM-GIS integration 15

15. Transformation - SFCGAL
geometry types aligned with OGC Simple Features Access standards:
Points, LineStrings, Polygons, TriangulatedSurfaces, PolyhedralSurfaces,
GeometryCollections, Solids
Operations: WKT reading and writing, Intersection operations and
predicates, Convex hull computation, Tessellation, Extrusion, Area and
distance computation, Minkovski sums, Contour offsets, Straight skeleton
generation
Available for PostGIS
http://www.sfcgal.org/
Open BIM: open-source solutions for BIM-GIS integration 16

16. Desktop – FreeCAD
3D parametric modeller via Arch
Workbench module
Open CASCADE
Built-in support for STEP (ifc)
Import/export: ifc, dae, obj,
https://www.freecadweb.org
Open BIM: open-source solutions for BIM-GIS integration 17

17. Visualisation - BIMSurfer
Requires BIMserver backend
WebGL 2.0
Focus on performance
https://github.com/opensourceBIM
/BIMsurfer
Open BIM: open-source solutions for BIM-GIS integration 18

18. Visualisation – CesiumJS
• An open specification by AGI that
allows for efficiently streaming 3D
geospatial data on the Web
• OGC Community Standard
• 3d syntax based on glTF
• Each tile desribed by one JSON file
with CRS, attribute, and
refinement information
Open BIM: open-source solutions for BIM-GIS integration 19

19. Conclusion
Open-source building blocks
available.
Let’s build!
Open BIM: open-source solutions for BIM-GIS integration 20