# ISurface.GetProjectedArea Method

Returns the projected area of the surface above or below an input z value.

[Visual Basic .NET]
**Public Function GetProjectedArea ( _**
**ByVal** *referenceHeight*** As **Double, _
**ByVal** *Type*** As **esriPlaneReferenceType _
**) As** Double

[C#]
**public **double** GetProjectedArea (**
double *referenceHeight,*
esriPlaneReferenceType *Type*
**);**

[C++]
**HRESULT GetProjectedArea(**
**double** referenceHeight,
**esriPlaneReferenceType** Type
**);**

[C++]
**Parameters**
*referenceHeight* [in]

* referenceHeight* is a parameter of type **double**
*Type* [in]

* Type* is a parameter of type **esriPlaneReferenceType**

#### Product Availability

Available with ArcGIS Engine, ArcGIS Desktop, and ArcGIS Server.

#### Description

Returns the 2D projected/planar area of the surface relative to a specified reference plane.

The plane used in the calculation is horizontal and is therefore defined simply by height. You indicate the height and whether the area is to be calculated above or below it.

Note, the area is not the 3D volume between the plane and the surface. Rather, think of the intersection between the plane and the surface. If you outline the intersection you end up with one or more polygons. If you want the projected area above the plane, it's the summed area of these polygons. If you want the area below the plane the polygons represent holes inside an outer polygon, the interpolation zone. The area below the plane is that of the interpolation zone minus the holes.

#### See Also

ISurface Interface