VisibilityOperator.TreeHeightInput Property
Gets or sets an input operator that provides tree heights above ground.
Syntax
public Operator TreeHeightInput { get; set; }Property Value
Default: null
An Operator that provides rasters containing tree heights above ground, in the VerticalUnit.
Remarks
The operator should give rasters with tree heights above ground. The heights must be expressed in the VerticalUnit. If the operator is Nil, or if it does not give any raster, the tree heights are assumed to be zero. The rasters do not have to be expressed in the same Coordinate Reference System as those from ElevationInput, since the tree-height rasters will be reprojected if necessary.
The rasters of tree heights may contain integers or floats.
If they contain integers, they may have any bit depth, but computations are done in 16 bits internally, and if a ground elevation plus a tree height is greater than 32767 (the greatest 16-bit integer, or 2^15 - 1), then it will be silently replaced by 32767.
If they contain floats, there are no such restrictions.
To gain speed, it is possible to compute in multiple resolutions; see the property FirstResolutionChange (not available for an AirspaceCoverageOperator). Ideally, the resolution levels available for tree heights should match those available for ground elevations, in both number and resolution. But this is not necessary, since the resolutions levels of elevations will control the computation, and the tree height input will be resampled accordingly.
If you have geodata of forest types but not of tree heights, you may use a RasterReclassificationOperator to convert the forest type to an estimated tree height. The following table of typical tree heights is collected from Nationalencyklopedin, http://www.ne.se.
tree | height |
|---|---|
Norway spruce | up to 60 m (seems to be a world record rather than a typical value) |
beech and elm | 30 - 40 m |
ash, pine, and lime-tree | up to 30 m |
birch, maple and hornbeam | up to 25 m |
oak | up to 25 m in Sweden, but up to 45 m in south Europe |
The derived operator VisibilityIndexOperator cannot distinguish the height of a tree as a sight obstacle from its height as a flight obstacle.
The derived operator TargetLineOfSightOperator uses trees only as sight obstacles, since its target positions are given explicitly, with altitudes above sea level.
The derived operator LineOfSightOperator expects that TreeHeightInput gives the heights of trees as sight obstacles, and its output will, by default, give the minimal visibility height above these treetops. However, if you want the minimal visibility heights above trees as flight obstacles, then you can postprocess the output from the LineOfSightOperator, although it is complicated. (Contact support.)
Example
// Set TreeHeightInput an configure the LineOfSightOperator for it
public static void ConfigureTreeHeightInput(
LineOfSightOperator lineOfSightOperator, Operator treeHeightInput)
{
// This property is a member of a type that might be referred to by a View
// or a GlobeView, either directly or indirectly through other objects, which means
// that you must use the Guard class to take the global configuration lock when it
// is modified to synchronize access with any running Carmenta Engine threads.
using (Guard guard = new Guard())
{
// Set the given TreeHeightInput
lineOfSightOperator.TreeHeightInput = treeHeightInput;
// Set the MinVisibilityHeightType to AbpoveTreetops
lineOfSightOperator.MinVisibilityHeightType = HeightType.AboveTreetops;
}
}
Platforms
Windows, Linux, Android