ISpatialReferenceResolution.ConstructFromHorizon Method

Defines the XY resolution and domain extent of this spatial reference based on the extent of its horizon. Low precision SRs will have minimum resolution of 1/10mm in current units.

[Visual Basic .NET]
Public Sub ConstructFromHorizon ( _
)

[C#]
public void ConstructFromHorizon (
);

[C++]
HRESULT ConstructFromHorizon(
void
);

Product Availability

Remarks

ConstructFromHorizon defines a domain extent and resolution sufficient to cover the horizon of a given coordinate system for high precision spatial references.  For low-precision spatial references the domain extent is centered on the horizon center. It does not define an extent for the Z- or M-domains; for these use methods available on ISpatialReference.

Projected Coordinate Systems

For a high precision ProjectedCoordinateSystem (PCS), ConstructFromHorizon defines the domain extent to be a square completely covering, and slightly larger than, the horizon extent of the PCS (which is an arbitrary rectangle). The scale factor (1/precision) is chosen to fit this domain.

For a low precision PCS, the center of the domain extent is aligned with the center of the horizon extent and expanded to achieve a target resolution of 1mm.

The example below lists high and low precision extents for WGS 1984 UTM Zone 11N.

Geographic Coordinate Systems

For a high precision GeographicCoordinateSystem (GCS), ConstructFromHorizon produces the square domain (-400, -400, 400, 400) (expressed in the units of the SR).  

For a low precision GCS the upper right hand corner is adjusted to achieve a default resolution of 1/500 of an arc-second.

Unknown Coordinate Systems

For an UnknownCoordinateSystem (UCS), the "horizon" is defined to be a square that produces a resolution of 1 millimeter for a low precision UCS or 1/10 mm for a high precision UCS.

The example below lists high and low precision extents for an UnknownCoordinateSystem.

See Also