# 5.4.3.35 IfcGrid

## 5.4.3.35.1 Semantic definition

IfcGrid ia a planar design grid defined in 3D space used as an aid in locating structural and design elements. The position of the grid (ObjectPlacement) is defined by a 3D coordinate system (and thereby the design grid can be used in plan, section or in any position relative to the world coordinate system). The position can be relative to the object placement of other products or grids. The XY plane of the 3D coordinate system is used to place the grid axes, which are 2D curves (for example, line, circle, arc, polyline).

The inherited attributes Name and Description can be used to define a descriptive name of the grid and to indicate the grid's purpose. A grid is defined by (normally) two, or (in case of a triangular grid) three lists of grid axes. The following figures/ shows some examples.

A grid may support a rectangular layout as shown in Figure 5.4.3.35.A, a radial layout as shown in Figure 5.4.3.35.B, or a triangular layout as shown in Figure 5.4.3.35.C.

Informal Propositions:

1. Grid axes, which are referenced in different lists of axes (UAxes, VAxes, WAxes) shall not be parallel.
2. Grid axes should be defined such as there are no two grid axes which intersect twice (see Figure 5.4.3.35.D).

## 5.4.3.35.4 Property sets

• Pset_Risk
• RiskName
• RiskType
• NatureOfRisk
• RiskAssessmentMethodology
• UnmitigatedRiskLikelihood
• UnmitigatedRiskConsequence
• UnmitigatedRiskSignificance
• MitigationPlanned
• MitigatedRiskLikelihood
• MitigatedRiskConsequence
• MitigatedRiskSignificance
• MitigationProposed
• AssociatedProduct
• AssociatedActivity
• AssociatedLocation
• Pset_Tolerance
• ToleranceDescription
• ToleranceBasis
• OverallTolerance
• HorizontalTolerance
• OrthogonalTolerance
• VerticalTolerance
• PlanarFlatness
• HorizontalFlatness
• ElevationalFlatness
• SideFlatness
• OverallOrthogonality
• HorizontalOrthogonality
• OrthogonalOrthogonality
• VerticalOrthogonality
• OverallStraightness
• HorizontalStraightness
• OrthogonalStraightness
• VerticalStraightness
• Pset_Uncertainty
• UncertaintyBasis
• UncertaintyDescription
• HorizontalUncertainty
• LinearUncertainty
• OrthogonalUncertainty
• VerticalUncertainty
• Qto_BodyGeometryValidation
• GrossSurfaceArea
• NetSurfaceArea
• GrossVolume
• NetVolume
• SurfaceGenusBeforeFeatures
• SurfaceGenusAfterFeatures

## 5.4.3.35.6 Formal representation

ENTITY IfcGrid
SUBTYPE OF (IfcPositioningElement);
UAxes : LIST [1:?] OF UNIQUE IfcGridAxis;
VAxes : LIST [1:?] OF UNIQUE IfcGridAxis;
WAxes : OPTIONAL LIST [1:?] OF UNIQUE IfcGridAxis;
PredefinedType : OPTIONAL IfcGridTypeEnum;
END_ENTITY;

## 5.4.3.35.7 References

### 5.4.3.35.8 Changelog

#### 5.4.3.35.8.1 IFC4

• attribute, PredefinedType
• where rule, HasPlacement
• where rule, WR41