Schema Central > NIEM 3.0 > geometryPrimitives.xsd > gml:patches

# gml:patches

`The patches property element contains the sequence of surface patches. The order of the elements is significant and shall be preserved when processing the array.`

## Element information

Properties: Global, Qualified

## Content

• Choice [0..*]
from subst. group gml:AbstractSurfacePatch
• gml:PolygonPatchA gml:PolygonPatch is a surface patch that is defined by a set of boundary curves and an underlying surface to which these curves adhere. The curves shall be coplanar and the polygon uses planar interpolation in its interior. interpolation is fixed to "planar", i.e. an interpolation shall return points on a single plane. The boundary of the patch shall be contained within that plane.
• gml:Trianglegml:Triangle represents a triangle as a surface patch with an outer boundary consisting of a linear ring. Note that this is a polygon (subtype) with no inner boundaries. The number of points in the linear ring shall be four. The ring (element exterior) shall be a gml:LinearRing and shall form a triangle, the first and the last position shall be coincident. interpolation is fixed to "planar", i.e. an interpolation shall return points on a single plane. The boundary of the patch shall be contained within that plane.
• gml:Rectanglegml:Rectangle represents a rectangle as a surface patch with an outer boundary consisting of a linear ring. Note that this is a polygon (subtype) with no inner boundaries. The number of points in the linear ring shall be five. The ring (element exterior) shall be a gml:LinearRing and shall form a rectangle; the first and the last position shall be coincident. interpolation is fixed to "planar", i.e. an interpolation shall return points on a single plane. The boundary of the patch shall be contained within that plane.
• from subst. group gml:AbstractGriddedSurface

None

## Sample instance

```<gml:patches>
<gml:PolygonPatch>
<gml:exterior>
<gml:LinearRing>...
</gml:LinearRing>
</gml:exterior>
<gml:interior>
<gml:LinearRing>...
</gml:LinearRing>
</gml:interior>
</gml:PolygonPatch>
</gml:patches>```

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