ArcObjects Library Reference (Geometry)  

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 ( _
public void ConstructFromHorizon (
HRESULT ConstructFromHorizon(

Product Availability

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


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.

Name Low Precision UnknownCoordinateSystem High Precision UnknownCoordinateSystem
MinX -1,073,741.8245 -450,359,962,737.05
MinY -1,073,741.8245 -450,359,962,737.05
MaxX 1,073,741.8225 450,359,962,737.049
MaxY 1,073,741.8225 450,359,962,737.049
Resolution 0.001 0.0001


See Also

ISpatialReferenceResolution Interface

.NET Snippets

Make Spatial Reference | Create High Precision Spatial Reference

.NET Samples

Create a custom raster type from the ground up for DMCII data (Code Files: DMCIIRasterType) | 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