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NgaDigitalTerrainElevationData Class

A terrain provider for reading terrain from National Geospatial-Intelligence Agency (NGA) Digital Terrain Elevation Data (DTED) files.
Inheritance Hierarchy
SystemObject
  AGI.Foundation.TerrainTerrainProvider
    AGI.Foundation.TerrainNgaDigitalTerrainElevationData

Namespace:  AGI.Foundation.Terrain
Assembly:  AGI.Foundation.TerrainReaders (in AGI.Foundation.TerrainReaders.dll) Version: 24.2.419.0 (24.2.419.0)
Syntax
public class NgaDigitalTerrainElevationData : TerrainProvider

The NgaDigitalTerrainElevationData type exposes the following members.

Constructors
  NameDescription
Public methodNgaDigitalTerrainElevationData(FileStreamFactory)
Initializes a new instance with the specified file stream factory for a DMED file.
Public methodNgaDigitalTerrainElevationData(String)
Initializes a new instance using the specified DMED filename.
Public methodNgaDigitalTerrainElevationData(FileStreamFactory, TerrainCacheGroup)
Initializes a new instance with the specified file stream factory for a DMED file.
Public methodNgaDigitalTerrainElevationData(String, TerrainCacheGroup)
Initializes a new instance using the specified DMED filename.
Public methodNgaDigitalTerrainElevationData(String, Int32, Int32, Int32, Int32)
Initializes a new instance with the specified information. If a DMED file is available for this data set, the constructor taking that file should be used instead.
Public methodNgaDigitalTerrainElevationData(String, Int32, Int32, Int32, Int32, TerrainCacheGroup)
Initializes a new instance with the specified information. If a DMED file is available for this data set, the constructor taking that file should be used instead.
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Properties
  NameDescription
Public propertyBoundingExtent
Gets or sets the smallest rectangular extent that bounds the terrain provided by this terrain provider. The returned extent's edges are expressed in radians.
(Inherited from TerrainProvider.)
Public propertyBoundingExtentNativeUnits
Gets or sets the smallest rectangular extent that bounds the terrain provided by this terrain provider. The returned extent's edges are expressed in the native units of the terrain provider.
(Inherited from TerrainProvider.)
Public propertyCacheGroup
Gets the TerrainCacheGroup that contains this provider.
Public propertyHeightReference
Gets or sets an enumeration indicating whether the heights returned by the GetHeight(Double, Double) method are relative to the Shape or to the ReferenceSurface.
(Inherited from TerrainProvider.)
Public propertyMinimumSampleSpacing
Gets the smallest distance between the successive height samples of the terrain data, in radians. If the return value is 0.0, then the minimum sample spacing is unknown.
(Overrides TerrainProviderMinimumSampleSpacing.)
Public propertyNativeToMeters
Gets or sets the value to multiply a height in the native units of the terrain provider to convert it to meters.
(Inherited from TerrainProvider.)
Public propertyRadiansToNative
Gets or sets the value to multiply an angle in radians by in order to convert it to the internal units of the terrain provider.
(Inherited from TerrainProvider.)
Public propertyReferenceSurface
Gets or sets the reference surface. The GetHeight(Double, Double) method returns heights relative to this reference surface. If this property is , the heights are relative to the surface of the Shape ellipsoid instead.
(Inherited from TerrainProvider.)
Public propertyShape
Gets or sets the shape on which the longitude and latitude are defined. If ReferenceSurface is , the heights returned by GetHeight(Double, Double) are relative to this ellipsoid as well.
(Inherited from TerrainProvider.)
Public propertyShapeFixedFrame
Gets or sets the reference frame fixed to the Shape in which the longitude and latitude are defined.
(Inherited from TerrainProvider.)
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Methods
  NameDescription
Public methodEquals
Determines whether the specified object is equal to the current object.
(Inherited from Object.)
Protected methodFinalize
Allows an object to try to free resources and perform other cleanup operations before it is reclaimed by garbage collection.
(Inherited from Object.)
Public methodGetFirstPartials
Get the partial derivatives of height with respect to the specified longitude and latitude relative to the provider's Shape.
(Overrides TerrainProviderGetFirstPartials(Double, Double).)
Public methodGetGradient

Get the interpolated gradient of height with respect to the terrain at the specified longitude and latitude relative to the provider's Shape. This method produces a vector representing the gradient of height in the ShapeFixedFrame.

Note: The direction for the gradient is defined for use as the outward facing surface normal direction. To obtain the directional derivative for the height (rate of change of height with respect to time), take the negative gradient and dot it with a unit vector along the desired azimuth (change in height with respect to distance), times the speed along that direction in meters/second.

The gradient, as defined above, is parallel to the upward facing terrain surface normal, but its magnitude indicates the rate of change in the height at that location.

(Inherited from TerrainProvider.)
Public methodGetHashCode
Serves as the default hash function.
(Inherited from Object.)
Public methodGetHeight
Gets the interpolated height of the terrain at the specified longitude and latitude using the default interpolator for this terrain provider.
(Overrides TerrainProviderGetHeight(Double, Double).)
Public methodGetHeightNativeUnits
Gets the interpolated height of the terrain at the specified longitude and latitude.
(Overrides TerrainProviderGetHeightNativeUnits(Double, Double).)
Public methodGetHeightRelativeToShape
Gets the interpolated height of the terrain at the specified longitude and latitude relative to the provider's Shape. This method takes into account the heights of any reference surfaces.
(Inherited from TerrainProvider.)
Public methodGetHessian

Get the interpolated hessian matrix based on the function of height with respect to the specified longitude and latitude relative to the provider's Shape. This method produces a matrix representing the mixed second order partial derivatives of height in the ShapeFixedFrame.

Note: The direction for the gradient and hessian is defined for use with the directional derivative on the surface. The gradient is defined to be orthogonal to the terrain surface with its surface projection in the direction of the greatest increase in the height. To obtain the second directional derivative for the height (acceleration of height along a particular azimuth), take the negative of the hessian then pre and post multiply it by the velocity vector along the desired azimuth. Then add the negative gradient dotted with the derivative of the velocity vector along the surface.

(Inherited from TerrainProvider.)
Public methodGetLocalMinimumSampleSpacing
Gets the smallest distance between the successive height samples of the terrain data, in radians, at the specified coordinates. If the return value is 0.0, then the minimum sample spacing is unknown.
(Inherited from TerrainProvider.)
Public methodGetNormal
Get the normal vector to the terrain surface at the specified location.
(Inherited from TerrainProvider.)
Public methodGetSecondPartials
Get the second order (mixed) partial derivatives of height with respect to the specified longitude and latitude relative to the provider's Shape.
(Overrides TerrainProviderGetSecondPartials(Double, Double).)
Public methodGetType
Gets the Type of the current instance.
(Inherited from Object.)
Protected methodInGlobalBounds
Returns if the coordinates are in global bounds which is: [-π, π] for longitude and [-π/2, π/2] for latitude.
(Inherited from TerrainProvider.)
Protected methodMemberwiseClone
Creates a shallow copy of the current Object.
(Inherited from Object.)
Public methodPreloadExtent
Loads the terrain data in a given CartographicExtent into the terrain cache. This method does not return until the terrain data is fully loaded. All terrain data within the extent is loaded into memory, even if doing so would exceed the TerrainCacheGroup'sMaximumSize. Furthermore, the loaded terrain data is locked in memory (meaning it will not be unloaded) until the user calls UnloadExtent(CartographicExtent). This method is safe to call from any thread.
(Overrides TerrainProviderPreloadExtent(CartographicExtent).)
Public methodToString
Returns a string that represents the current object.
(Inherited from Object.)
Public methodUnloadExtent
Unloads the cached terrain data for a given CartographicExtent. This method unloads all cached regions where any part of the region falls within the extent. It does not return until the regions have been unloaded. However, if a region within the extent is being used in another thread while this method is executing, the region may be reloaded immediately after this method unloads it. This method is safe to call from any thread.
(Overrides TerrainProviderUnloadExtent(CartographicExtent).)
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See Also