Create No Target LoS

Creates a line-of-sight between each point in the observers layer and the targets layer, where the Observer ID field value from the observer matches the Target and Observer agreement ID field of the target. This ensures that each point in the targets layer is linked to one point in the observers layer. Each line-of-sight starts at the observer and ends at the edge of the DEM raster behind the target.

The target points can be and usually should be created by tools Create points around and Create points in direction.

This variant of the algorithm allows elevation extraction from multiple rasters. The rasters are ordered from smallest cell size to the biggest. Elevation is always obtained from raster with smallest cell size that has valid elevation value (no data is not considered as valid value). This allows utilization of DEM with large cells as addition to DEM with smaller cells. For example DEM with cell size 1 meter can be used within city for areas close to observers and SRTM data (30 meter cell size) in areas around the city, far from the observer.

This variant of the tool specifies sampling and length of LoS by table Sampling distance - distance table. This a special kind of table, which can be output of tools Calculate Object Distances and Calculate Object Sizes, that specifies sampling distance and distance limits. Each row in the table specifies sampling distance (size) on LoS for distances lower then distance. Two rows with values of sizes 1 and 5 and distance 1000 and 3000 mean that LoS will be sampled every 1 meter for distance lower then 1000 meters and then each 5 meters for distances lower then 3000 meter from observer. The length of LoS will be limited to 3000 meters. To specify unlimited LoS length a row with distance value -1 and sampling distance must be present (this is interpreted as maximal possible length with respect to raster data).

Parameters

Label Name Type Description
Raster Layer DEM DemRasters [raster][list] List of DEM rasters on which the LoS is calculated. The rasters are ordered from smallest spatial resolution to highest. Elevation for the LoS is taken from the raster with the smallest spatial resolution that has a value.
Sampling distance - distance table LineSettingsTable [vector: nogeometry] Distance table specifying the sampling size on the LoS by distance.
Observers point layer ObserverPoints [vector: point] Point layer representing the observers.
Observer ID field ObserverIdField [tablefield: numeric] Field containing IDs for observer points.
Observer offset field ObserverOffset [tablefield: numeric] Field containing the offset above DEM for observer points.
Targets point layer TargetPoints [vector: point] Point layer representing the targets.
Target ID field TargetIdField [tablefield: numeric] Field containing IDs for target points.
Target and Observer agreement ID field TargetDefinitionIdField [tablefield: numeric] Field that specifies which target point is linked to which observer point. Values in this field are compared to the ObserverIdField.
Output layer OutputLayer [vector: line] Output layer containing the LoS.

Outputs

Label Name Type Description
Output layer OutputLayer [vector: line] Output layer containing the LoS.

Fields in the output layer

  • los_type - string - for this tool the values is always without target
  • id_observer - integer - value from field specified in Observer ID field
  • id_target - integer - value from field specified in Target ID field
  • observer_offset - double - value from the field specified in Observer offset field
  • azimuth - double - value from the field specified in Target offset field
  • target_x - double - X coordinate of point in Targets point layer, used later in analyses
  • target_y - double - Y coordinate of point in Targets point layer, used later in analyses
  • angle_step_between_los - double - difference between LoS from one viewpoint as angle (degrees)

Tool screenshot

Create no target LoS