![]() The greatest distance at which lights in the vicinity of 1000 candelas can be seen and identified against an unlit black background. The greatest safe distance at which a black object of suitable dimensions, situated near the ground, can be seen and recognised when observed against a bright background Visibility for aeronautical purposes is the greater of: Visibility ( inRaster, inObserverFeatures, algOutput, analysisType, nonVisibleValue, zFactor, useEarthCurvature, refractivit圜oefficient, surfaceOffset, observerElevation, observerOffset, innerRadius, outerRadius, horizStartAngle, horizEndAngle, vertUpperAngle, vertLowerAngle ) # Save the output outvis. checkOutExtension ( "Spatial" ) # Execute Visibility outvis = arcpy. workspace = "c:/sapyexamples/data" # set local variables inRaster = "elevation" inObserverFeatures = "observers.shp" aglOutput = "c:/sapyexamples/output/aglout1" analysisType = "OBSERVERS" nonVisibleValue = "ZERO" zFactor = 1 useEarthCurvature = "CURVED_EARTH" refractivit圜oefficient = 0.13 surfaceOffset = 500 observerElevation = 2000 observerOffset = 500 innerRadius = 20000 outerRadius = 100000 horizStartAngle = 45 horizEndAngle = 215 vertUpperAngle = 5 vertLowerAngle = - 5 # Check out the ArcGIS Spatial Analyst extension license arcpy. # Requirements: Spatial Analyst Extension # Import system modules import arcpy from arcpy import env from arcpy.sa import * # Set environment settings env. # Name: Visibility_Ex_02.py # Description: Determines the raster surface locations visible to a set of # observer features. The output will either record the number of times that each cell location in the input surface raster can be seen by the input observation locations (the frequency analysis type), or record which observer locations are visible from each cell in the raster surface (the observers type). If this parameter is unspecified and the default field does not exist in the input observer features attribute table, it defaults to -90. You may overwrite it by specifying another numerical field or a value. ![]() You can select a field in the input observers dataset, or you can specify a numerical value.īy default, a numerical field VERT2 is used if it exists in the input observer features attribute table. The value for this parameter must be less than the Vertical Upper Angle parameter. The allowed range is from -90 up to (but not including) 90. The value is specified in degrees, and can be integer or floating point. This value defines the lower vertical angle limit of the scan relative to the horizontal plane. Syntax Visibility(in_raster, in_observer_features, ) Parameter See Analysis environments and Spatial Analyst for additional details on the geoprocessing environments that apply to this tool. ![]() An example of when an input raster may be resampled is when the output coordinate system, extent, or cell size is different from that of the input. When the input raster needs to be resampled, the bilinear technique will be used. For example, through the observer offset parameter, you may specify an offset to the observer elevation in the visibility analysis. Use the observer parameters to gain more control over the visibility analysis process. When the input observer features contain multiple observers, the output value is the minimum of the AGL values from all of the individual observers. Each cell on the AGL output raster records the minimum height that needs to be added to that cell to make it visible by at least one observer. If the point lies above the local horizon, it is considered visible.Īn optional above-ground-level (AGL) output raster is provided by the tool. The local horizon is computed by considering the intervening terrain between the point of observation and the current cell center. The visibility of each cell center is determined by comparing the altitude angle to the cell center with the altitude angle to the local horizon. If the input raster contains undesirable noise caused by sampling errors, you can smooth the raster with a low-pass filter, such as the Mean option of Focal Statistics, before running this tool. For the other, it identifies which observers are visible from each raster surface location. ![]() For the first type, the tool determines which raster surface locations are visible to a set of observers. This tool supports two visibility analysis types, Frequency and Observers, which is controlled by the Analysis type tool parameter. Illustration Visibility output with the Frequency option, displayed on a hillshaded elevation surface Visibility output with the Observers option, displayed on a hillshaded elevation surface Usage Determines the raster surface locations visible to a set of observer features, or identifies which observer points are visible from each raster surface location.
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