ISpatialReference3.ProjectionHint Method

Projection hint for speeding up projections.

[Visual Basic .NET]
Public Sub ProjectionHint ( _
    ByVal Geometry As IGeometry, _
    ByVal targetSR As ISpatialReference, _
    ByRef direction As esriTransformDirection, _
    ByRef pXForm As ITransformation, _
    ByRef ProjectionHint As Integer _
)

[C#]
public void ProjectionHint (
    IGeometry Geometry,
    ISpatialReference targetSR,
    ref esriTransformDirection direction,
    ref ITransformation pXForm,
    ref int ProjectionHint
);

[C++]
HRESULT ProjectionHint(
  IGeometry* Geometry,
  ISpatialReference* targetSR,
  esriTransformDirection* direction,
  ITransformation** pXForm,
  long* ProjectionHint
);

[C++]
Parameters
Geometry 
  Geometry is a parameter of type IGeometry
targetSR 
  targetSR is a parameter of type ISpatialReference
direction [in, out]
  direction is a parameter of type esriTransformDirection
pXForm [in, out]
  pXForm is a parameter of type ITransformation
ProjectionHint [in, out]
  ProjectionHint is a parameter of type long

Product Availability

Description

Each geographic or projected coordinate system has a horizon. The horizon defines the mathematical limits of the coordinate system. As an example, transverse Mercator is limited to longitude values that are within +/-45 degrees of the central meridian. Most projection workflows are local. That is, all geometries of a feature class are within the horizons of the input and output coordinate systems. The process of checking whether a geometry is within, crosses, or is outside a horizon takes time. You can use the projectionhint method to calculate whether the envelope or bounding geometry of a feature class is within the applicable horizons. If it is, you can add a flag to the ProjectEx5 method to omit horizon checking.

You can also have the projectionhint method check for a geographic (datum) transformation. In the SpatialReferenceEnvironment, the GeoTransformationOperationSet stores active transformations. Normally, none are loaded by default, but if you've loaded several transformations previously, you can use projection hint to return the appropriate one and in which direction to apply it for this projection operation.

The projectionhint values are:

  esriProjectionHintNoHorizonCheck        =  0,
  esriProjectionHintCheckPCSHorizon       =  1,
  esriProjectionHintCheckGCSHorizon       =  2,
  esriProjectionHintFindGeoTransformation =  4,
  esriProjectionHintDefault               =  7,
  esriProjectionHintExplore               =  8,
  esriProjectionHintDoNotProject          = 16  // useful for isEqualNoName

See Also