ElevationMaskFromTerrain Method (TerrainProvider, Double, Double, Cartographic, Double, Double, Double, Boolean, ITrackCalculationProgress)

public static List<ElevationMask> FromTerrain(
	TerrainProvider provider,
	double minimumTerrainHeight,
	double maximumTerrainHeight,
	Cartographic observerPosition,
	double stepSize,
	double maximumSearchAngle,
	double[] azimuths,
	bool multithreadComputations,
	ITrackCalculationProgress tracker
)

Public Shared Function FromTerrain ( 
	provider As TerrainProvider,
	minimumTerrainHeight As Double,
	maximumTerrainHeight As Double,
	observerPosition As Cartographic,
	stepSize As Double,
	maximumSearchAngle As Double,
	azimuths As Double(),
	multithreadComputations As Boolean,
	tracker As ITrackCalculationProgress
) As List(Of ElevationMask)

public:
static List<ElevationMask^>^ FromTerrain(
	TerrainProvider^ provider, 
	double minimumTerrainHeight, 
	double maximumTerrainHeight, 
	Cartographic observerPosition, 
	double stepSize, 
	double maximumSearchAngle, 
	array<double>^ azimuths, 
	bool multithreadComputations, 
	ITrackCalculationProgress^ tracker
)

static member FromTerrain : 
        provider : TerrainProvider * 
        minimumTerrainHeight : float * 
        maximumTerrainHeight : float * 
        observerPosition : Cartographic * 
        stepSize : float * 
        maximumSearchAngle : float * 
        azimuths : float[] * 
        multithreadComputations : bool * 
        tracker : ITrackCalculationProgress -> List<ElevationMask> 

Parameters

provider

Type: AGI.Foundation.TerrainTerrainProvider
The source of terrain from which to compute the masks.

minimumTerrainHeight

Type: SystemDouble
The minimum height in meters that can be returned by the TerrainProvider's GetHeightRelativeToShape(Double, Double) method. Setting this value lower than necessary will not affect the results, but it will decrease performance. Setting it too high can cause incorrect results.

maximumTerrainHeight

Type: SystemDouble
The maximum height in meters that can be returned by the TerrainProvider's GetHeightRelativeToShape(Double, Double) method. Setting this value higher than necessary will not affect the results, but it will decrease performance. Setting it too low can cause incorrect results.

observerPosition

Type: AGI.Foundation.CoordinatesCartographic
The planetodetic position of the stationary observer at which the masks are computed.

stepSize

Type: SystemDouble
The size of the step along each azimuth ray, in radians.

maximumSearchAngle

Type: SystemDouble
The maximum angle, in radians, to move along each azimuth ray in constructing the masks.

azimuths

Type: SystemDouble
The azimuths, in radians, along which to compute the elevation masks.

multithreadComputations

Type: SystemBoolean
Indicates whether the computations should be multithreaded.

tracker

Type: AGI.FoundationITrackCalculationProgress
The object to which progress is reported and that is able to cancel this operation before it is complete, or . When reporting progress, the 'additionalInformation' parameter to ReportProgress(Int32, Object) will be .

Return Value

This method works by casting a ray out from the observerPosition along a specified direction to determine the minimum elevation angle that is visible above the terrain in that direction. More specifically, the various distances at which the minimum elevation angle increases in that direction are determined.

stepSize is the distance between steps along the ray, in radians. A reasonable value for this parameter would sample approximately three times per terrain grid cell.

maximumSearchAngle is the maximum angle, in radians, to move along each ray. In other words, this parameter indicates the stopping point for sampling along the ray. A reasonable value will take into account the difference between the maximum and minimum heights of terrain provided by provider and potentially how close together the minimum and maximum heights are located.

Examples

double approximateHeightOfMtEverest = 8850.0;
double semimajorAxisLength = WorldGeodeticSystem1984.Shape.SemimajorAxisLength;
double maximumSearchAngle = Math.Acos(semimajorAxisLength / (semimajorAxisLength + approximateHeightOfMtEverest));

Reference