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.

Name	Low Precision ProjectedCoordinateSystem	High Precision ProjectedCoordinateSystem
MinX	-573,741.824	-5,120,900.0
MinY	-1,073,741.824	-9,998,100.0
MaxX	1,573,741.823	14,875,300.0
MaxY	1,073,741.823	9,998,100.0
Resolution	0.001	2.2 x 10^-9

 

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.

Name	Low Precision GeographicCoordinateSystem	High Precision GeographicCoordinateSystem
MinX	-400	-400
MinY	-400	-400
MaxX	793.046469444444	400
MaxY	793.046469444444	400
Resolution	5.55555555555556E-07 (1/500 arc-second)	8.8 x 10^-14

 

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

ISpatialReferenceResolution Interface

.NET Snippets

Create High Precision Spatial Reference | Make Spatial Reference |

.NET Samples

Creating a toolbar of globe tools (Code Files: SpatialReference) |

.NET Related Topics

Constructing a high- or low-precision spatial reference | Creating feature classes | How to import or export a spatial reference | Working with GeometryEnvironment |