AirspaceCoverageOperator Class
Computes and merges viewsheds of multiple observers according to customizable settings.
NuGet/Assembly: Carmenta.Engine.5.16.2.nupkg (in the CEOperators assembly)
Syntax
public class AirspaceCoverageOperator : LineOfSightOperatorRemarks
There is an introductory Visibility Guide, which you can read in parallel with this reference manual. There is also a sample configuration airspace_coverage.px that you can try out in Carmenta Explorer.
AirspaceCoverageOperator is a variation of LineOfSightOperator that, in addition to calculating viewsheds, also merges the generated viewsheds according to a customizable condition. The most basic use case, which is also the default behavior for this operator, is to provide the union of all viewsheds. More complicated analysis is also possible, such as finding areas covered by at least two viewsheds of one type and one of another type; see MinObservers and ObserverTypeConditions for information on how to customize the merging behavior.
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AirspaceCoverageOperator internally works with a three-dimensional volume representation of the viewsheds and can hence handle arbitrary vertical overlaps of viewsheds (including partial overlaps).
All output types supported by LineOfSightOperator are also supported by this operator. In addition, this operator provides OutputCoverageRaster.
Internally, the operator represents altitudes above sea level in meters as signed 16-bit integers, and the two largest such integers have special meanings, so the highest representable altitude is 32 765 meters above sea level.
This operator uses the global cache to store its calculated output features, so it can often reuse a cached result instead of recomputing it. Note that changing any properties of the operator, any ObserverInput features or the AreaOfInterestInput will automatically invalidate the cached features.
To be able to cache and reuse its merged results well, the operator is very greedy when requesting features from ObserverInput and AreaOfInterestInput: it will always request data from these inputs from the whole world, regardless of the current View.Area. So, to avoid overwhelming the operator, your application must ensure that the memory dataset of observers contains only a limited number of point features that are all near the area of interest, or near each other if no area of interest is given.
Using a layer with a dynamic cache mode
The operator also supports the OrdinaryLayer cache modes Dynamic and DynamicAsync, which is unique since the operator will merge several input features into one output feature: such merging is normally impossible under a dynamic cache mode. When a dynamic cache mode is used, the ID-giving input will be the ObserverInput. If all features coming from the ObserverInput originate in the same MemoryDataSet, your application can ask for a refreshed presentation in one of two ways: either call
MemoryDataSet.RefreshFeaturePresentation(feature, false)
for a specific feature that has been edited, or call
MemoryDataSet.RefreshAllFeaturePresentation(false).
The OrdinaryLayer will understand that even if just one feature is asked to be refreshed, the entire dynamic cache must be flushed since any single feature may affect the whole result from this operator. This means that if a configuration with an AirspaceCoverageOperator is opened in Carmenta Explorer, the usual editing tool will ensure that the dynamic cache is updated when observers are edited. However, if the observer features originate in two or more memory datasets, then the application must call
MemoryDataSet.RefreshAllFeaturePresentation(false).
The AreaOfInterestInput, if any, will usually get data from another memory dataset, but note that this is not the ID-giving input, which means that the dynamic cache will assume that these data are static. So, special application logic is needed to handle modifications of the area of interest; see OrdinaryLayerCacheMode for details. Unfortunately, this is not something that Carmenta Explorer will do automatically. So when trying out configurations in Carmenta Explorer, it is best to let the area-of-interest polygon be displayed in a non-selectable layer, so that it cannot be edited.
Inheritance Hierarchy
System.Object (not available in C#)
EngineObject
Operator
VisibilityOperator
LineOfSightOperator
AirspaceCoverageOperator
Platforms
Windows, Linux, Android
AirspaceCoverageOperator Members
The AirspaceCoverageOperator type has the following members.
Constructors
| Name | Description |
|---|---|
| AirspaceCoverageOperator | Initializes a new instance of the AirspaceCoverageOperator class. |
Properties
| Name | Description |
|---|---|
| AreaOfInterestBottomElevation | Gets or sets the bottom elevation of the area of interest, in meters above sea level. |
| AreaOfInterestInput | Gets or sets the input operator that provides a polygon feature that defines the area of interest. |
| AreaOfInterestTopElevation | Gets or sets the top elevation of the area of interest, in meters above sea level. |
| AuxiliaryRasterInput | Gets or sets an input operator that provides additional raster data for CustomPropagation. Inherited from LineOfSightOperator |
| CarrierType | Gets or sets an enumeration value, telling if the observer is ground-based or airborne. Inherited from LineOfSightOperator |
| CustomPropagation | Gets or sets a custom propagation proxy object that refers to custom-written code for propagation. Inherited from LineOfSightOperator |
| Description | Gets or sets a short description of the operator. Inherited from Operator |
| DesiredInputResolution | Gets or sets the desired resolution for the calculation nearest the observers, in meters. Inherited from VisibilityOperator |
| DisplayName | Gets or sets a display name for the operator. Inherited from Operator |
| DistanceVariation | Gets or sets a value that tells how the range of the observer varies with the direction (Constant or PhasedArray). Inherited from VisibilityOperator |
| ElevationInput | Gets or sets the operator that provides elevation data. Inherited from VisibilityOperator |
| EnableEvents | Gets or sets a flag that determines whether the operator shall fire events for a progress bar. Inherited from VisibilityOperator |
| InterpolatedCells | Gets or sets a value, telling how far away from the observer elevations should be interpolated. Inherited from LineOfSightOperator |
| IsDisposed | Gets a value that tells whether the current AirspaceCoverageOperator has been disposed. Inherited from EngineObject |
| IsoMetadataDocument | Gets or sets the path to an ISO 19139 metadata document for the operator. Inherited from Operator |
| MaxDistance | Gets or sets the maximal range of the observer, in meters. Inherited from VisibilityOperator |
| MaxDistanceType | Gets or sets the type of maximal distance (horizontal or three-dimensional). Inherited from LineOfSightOperator |
| MaxUpDistance | Gets or sets the maximal straight-up range of the observer. Inherited from LineOfSightOperator |
| MinDistance | Gets or sets the minimal range of the observer. Inherited from LineOfSightOperator |
| MinObservers | Gets or sets the minimum number of observers that are sufficient to cover a point, regardless of observer type. |
| MinVisibilityHeightType | Gets or sets the type of visibility heights in the output (above sea-level, ground or treetops). Inherited from LineOfSightOperator |
| Mode | Whether to output the merged volume, its complement, or both. |
| Name | Gets or sets the name of the operator. Inherited from Operator |
| NativeHandle | Gets the native Carmenta Engine kernel object the current AirspaceCoverageOperator represents. Inherited from EngineObject |
| ObserverHeightType | Gets or sets the type of height used for an observer (above sea-level, ground or treetops). Inherited from VisibilityOperator |
| ObserverInput | Gets or sets the input operator that gives features that represent observers. Inherited from LineOfSightOperator |
| ObserverTypeAttribute | Gets or sets the observer-type attribute name. |
| ObserverTypeConditions | Gets a collection of alternative instances of ObserverTypeCondition. |
| OutputCoverageRaster | Gets or sets whether to output coverage-raster features. |
| OutputMinVisibilityHeights | Gets or sets whether the operator shall output rasters containing in each cell the minimum height that is visible to the observer. Inherited from LineOfSightOperator |
| OutputVolumeEncodingRaster | Gets or sets whether the operator should output volume-encoding rasters. Inherited from LineOfSightOperator |
| OutputVolumeMesh | Gets or sets whether the operator should output mesh features that represent volumes. Inherited from LineOfSightOperator |
| PictureDirection | Gets or sets the main direction of observation. Inherited from VisibilityOperator |
| PictureElevation | Gets or sets the elevation angle of the observer. Inherited from VisibilityOperator |
| PictureHeight | Gets or sets the height of the picture that the observer sees. Inherited from VisibilityOperator |
| PictureWidth | Gets or sets the width of the picture that the observer sees. Inherited from VisibilityOperator |
| Refraction | Gets or sets a value that models the effects of refraction in the atmosphere. Inherited from VisibilityOperator |
| SampleInterval | Gets or sets the distance between sample points, when the observer feature is a line. Inherited from LineOfSightOperator |
| SecondPictureBackwards | Gets or sets a flag, telling if the observer looks in two opposite directions at once. Inherited from VisibilityOperator |
| SensorHeight | Gets or sets the sensor height. Inherited from VisibilityOperator |
| TreeHeightInput | Gets or sets an input operator that provides tree heights above ground. Inherited from VisibilityOperator |
| UndefinedElevationInterpretation | Gets or sets the interpretation of the undefined elevation. Inherited from LineOfSightOperator |
| IUserProperties.UserProperties | Gets the AttributeSet that contains the user properties. Inherited from IUserProperties |
| VerticalRotationAxis | Gets or sets a flag that determines the exact shape of the rectangular cross-section of the lobe. Use True for a radar system with a vertical rotation axis; use False for a camera with fixed orientation. Inherited from VisibilityOperator |
| VerticalUnit | Gets or sets the unit for elevations and vertical distances except maxUpDistance. Inherited from VisibilityOperator |
Methods
| Name | Description |
|---|---|
| Clone | Creates a copy of an object. Inherited from EngineObject |
| Dispose | Releases the reference to the native Carmenta Engine kernel instance the EngineObject represents. Inherited from EngineObject |
| Equals | Determines whether this instance is equal to another. Inherited from EngineObject |
| FindChildObject | Overloaded. Finds the child object with the specified name. Inherited from Operator |
| FlushCache | Marks the layer as flushed which will release cached resources during the next update. Inherited from Operator |
| GetChildObjects | Overloaded. Gets the child objects of the current object. Inherited from Operator |
| GetFeatures | Overloaded. Gets features from the operator chain. Inherited from Operator |
| GetLocalizedDescription | Gets a localized version of the operator description in a specific language. Inherited from Operator |
| GetLocalizedDisplayName | Gets a localized version of the operator display name in a specific language. Inherited from Operator |
| GetLocalizedIsoMetadataDocument | Gets the path to an ISO 19139 metadata document for a specific language. Inherited from Operator |
| GetRasterFeature | Overloaded. Gets raster features from the operator chain and merges them into a single raster. Inherited from Operator |
| HasLocalizedDescription | Checks if a localized version of the operator description is available in a specific language. Inherited from Operator |
| HasLocalizedDisplayName | Checks if a localized version of the operator display name is available in a specific language. Inherited from Operator |
| HasLocalizedIsoMetadataDocument | Checks if an ISO 19139 metadata document is available for a specific language. Inherited from Operator |
| SetLocalizedDescription | Sets a operator description in a specific language. Inherited from Operator |
| SetLocalizedDisplayName | Sets a operator display name in a specific language. Inherited from Operator |
| SetLocalizedIsoMetadataDocument | Sets the path to an ISO 19139 metadata document for the operator, for a specific language. Inherited from Operator |