Observer Points (Spatial Analyst)

License Level:BasicStandardAdvanced

Summary

Identifies which observer points are visible from each raster surface location.

Learn more about how Observer Points works

Usage

Syntax

ObserverPoints (in_raster, in_observer_point_features, {z_factor}, {curvature_correction}, {refractivity_coefficient}, {out_agl_raster})
ParameterExplanationData Type
in_raster

The input surface raster.

Raster Layer
in_observer_point_features

The point feature class that identifies the observer locations.

The maximum number of points allowed is 16.

Feature Layer
z_factor
(Optional)

Number of ground x,y units in one surface z unit.

The z-factor adjusts the units of measure for the z units when they are different from the x,y units of the input surface. The z-values of the input surface are multiplied by the z-factor when calculating the final output surface.

If the x,y units and z units are in the same units of measure, the z-factor is 1. This is the default.

If the x,y units and z units are in different units of measure, the z-factor must be set to the appropriate factor, or the results will be incorrect. For example, if your z units are feet and your x,y units are meters, you would use a z-factor of 0.3048 to convert your z units from feet to meters (1 foot = 0.3048 meter).

Double
curvature_correction
(Optional)

Allows correction for the earth's curvature.

  • FLAT_EARTH No curvature correction will be applied. This is the default.
  • CURVED_EARTH Curvature correction will be applied.
Boolean
refractivity_coefficient
(Optional)

Coefficient of the refraction of visible light in air.

The default value is 0.13.

Double
out_agl_raster
(Optional)

The output above ground level (AGL) raster.

The AGL result is a raster where each cell value is the minimum height that must be added to an otherwise nonvisible cell to make it visible by at least one observer.

Cells that were already visible will have a value of 0 in this output raster.

Raster

Return Value

NameExplanationData Type
out_raster

The output raster.

The output identifies exactly which observer points are visible from each raster surface location.

Raster

Code Sample

ObserverPoints example 1 (Python window)

This example identifies exactly which observer points are visible from each raster surface location.

import arcpy
from arcpy import env
from arcpy.sa import *
env.workspace = "C:/sapyexamples/data"
outObsPoints = ObserverPoints("elevation","observers.shp", 1, "CURVED_EARTH", 0.13)
outObsPoints.save("C:/sapyexamples/output/outobspnt01")
ObserverPoints example 2 (stand-alone script)

This example identifies exactly which observer points are visible from each raster surface location.

# Name: ObserverPoints_Ex_02.py
# Description: Identifies exactly which observer points are visible 
#              from each raster surface location.
# Requirements: Spatial Analyst Extension

# Import system modules
import arcpy
from arcpy import env
from arcpy.sa import *

# Set environment settings
env.workspace = "C:/sapyexamples/data"

# Set local variables
inRaster = "elevation"
inObsPoints = "observers.shp"
zFactor = 1
useEarthCurv = "CURVED_EARTH"
refractionVal = 0.13

# Check out the ArcGIS Spatial Analyst extension license
arcpy.CheckOutExtension("Spatial")

# Execute ObserverPoints
outObsPoints = ObserverPoints(inRaster, inObsPoints, zFactor, 
                              useEarthCurv, refractionVal)

# Save the output 
outObsPoints.save("C:/sapyexamples/output/outobspnt02")

Environments

Related Topics

Licensing Information

ArcGIS for Desktop Basic: Requires Spatial Analyst or 3D Analyst
ArcGIS for Desktop Standard: Requires Spatial Analyst or 3D Analyst
ArcGIS for Desktop Advanced: Requires Spatial Analyst or 3D Analyst
4/10/2014