IHorizontalDatum Interface Reference

A way to convert a geographical position between a local horizontal datum and WGS84. More...

import "_encxcom_encx.idl";

Inheritance diagram for IHorizontalDatum:

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List of all members.

Public Member Functions
HRESULT	LocalToWGS84 ([out] DOUBLE *LatWGS84,[out] DOUBLE *LonWGS84,[in] DOUBLE LatLocal,[in] DOUBLE LonLocal,[out, retval] VARIANT_BOOL *bRes)
	Convert a geopgraphical position on the local datum to WGS84.
HRESULT	WGS84ToLocal ([out] DOUBLE *LatLocal,[out] DOUBLE *LonLocal,[in] DOUBLE LatWGS84,[in] DOUBLE LonWGS84,[out, retval] VARIANT_BOOL *bRes)
	Convert a geopgraphical position on WGS84 to the local datum.
Properties
DOUBLE *	ErrorDistanceMetres [get]
	The accuracy of the transformation. Units are metres.
VARIANT_BOOL *	HasLocalDatum [get]
	Returns true if the chart has a local datum which is not WGS84.
BSTR *	LocalDatumShortName [get]
	The local datum name in either long or short form. See HCRF 2.0 A.4 HORIZONTAL DATUM CODES.
BSTR *	LocalDatumLongName [get]
	The local datum name in either long or short form. See HCRF 2.0 A.4 HORIZONTAL DATUM CODES.

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Detailed Description

A way to convert a geographical position between a local horizontal datum and WGS84.

A horizontal datum may be provided for each panel on a raster chart.

Definition at line 664 of file _encxcom_encx.idl.

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Member Function Documentation

HRESULT IHorizontalDatum::LocalToWGS84	(	[out] DOUBLE *	LatWGS84,
		[out] DOUBLE *	LonWGS84,
		[in] DOUBLE	LatLocal,
		[in] DOUBLE	LonLocal,
		[out, retval] VARIANT_BOOL *	bRes
	)

Convert a geopgraphical position on the local datum to WGS84.

Returns false if the position is outside the area of the datum - the conversion will still be performed but will be less accurate.

HRESULT IHorizontalDatum::WGS84ToLocal	(	[out] DOUBLE *	LatLocal,
		[out] DOUBLE *	LonLocal,
		[in] DOUBLE	LatWGS84,
		[in] DOUBLE	LonWGS84,
		[out, retval] VARIANT_BOOL *	bRes
	)

Convert a geopgraphical position on WGS84 to the local datum.

Returns false if the position is outside the area of the datum - the conversion will still be performed but will be less accurate.

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Property Documentation

DOUBLE* IHorizontalDatum::ErrorDistanceMetres [get]

The accuracy of the transformation. Units are metres.

VARIANT_BOOL* IHorizontalDatum::HasLocalDatum [get]

Returns true if the chart has a local datum which is not WGS84.

Some ARCS charts use a local datum other than WGS84. ARCS polynomials support non-linear datum shifts (see Admiralty List of Radio Signals Volume 8 NP288 for an explanation).

Raster charts which do not have accurate WGS84 transformation polynomials behave as charts with a local datum. In this case the offset (between local and WGS84) is linear and determined by CRasPanelInfo::ManualWGS84Shift(). The default is zero.

Typically local datum conversions are only needed when dealing with external position information which is in the same local datum as the chart.

BSTR* IHorizontalDatum::LocalDatumShortName [get]

The local datum name in either long or short form. See HCRF 2.0 A.4 HORIZONTAL DATUM CODES.

BSTR* IHorizontalDatum::LocalDatumLongName [get]

The local datum name in either long or short form. See HCRF 2.0 A.4 HORIZONTAL DATUM CODES.