Line of Sight Tools

The following line of sight tools are available:

§  Line of Sight Analysis Tool

§  Viewshed Tool

§  Viewshed on Route Tool

§  Threat Dome Tool

§  Buffer Query Tool

Line of Sight Tool

The Line of Sight tool provides a visual indication of whether specific locations in the 3D World can be seen from a selected position. The tool displays a visual marker for the existence of a line of sight from a single observer position to multiple positions in the world.

This feature takes into account the observer’s viewpoint, direction of sight and distance of sight, to portray which locations can be viewed from the viewpoint, and which locations cannot be viewed. The observer and target positions can be set at any altitude above the terrain.

Using the Line of Sight Analysis Tool

To use the Line of Sight Analysis tool:

1.      On the Analysis tab, in the Line of Sight group, click Line of Sight.

2.      In the Line of Sight Analysis property sheet, enter the following parameters:

a.      In the Analysis section, in the Sampling Interval field, enter the desired value for the sample resolution of your measurement. This value represents the distance between terrain samples for the measurement along each line. A smaller sample size is more accurate but slower to calculate.

b.      In the Observer section, in the Height field, enter the desired value for the altitude of the observer.

Note: The X and Y observer position fields in the Observer section are derived from the point you select in the 3D Window (see below). They only become enabled after you place the Observer point, so you can modify the values as required in the property sheet.

c.      In the Targets section, in the Height field, enter the desired value for the altitude of the target point or points.

3.      Once you have set the necessary parameters, click the cursor to define your viewpoint for the observer.

4.      Click in the 3D Window to place the target points. You must place at least one point in the 3D Window.

5.      Right-click to finish the operation. At this point, TerraExplorer Pro begins to calculate the line of sight. This process can take a few seconds.

6.      Once the Line of Sight Analysis has been completed, you can edit the parameters and recalculate, or close the property sheet to finish the operation.

Once completed, a single line, or group of lines, marked on the terrain appear between the viewpoint and the endpoint. Target points that are visible from the observer viewpoint are colored green, whereas points that are not visible from the observer viewpoint are colored red.

Note:    To perform another line of sight measurement, you must first close the property sheet either by clicking Close  on the property sheet, or by clicking again the Line of Sight command on the Analysis tab.

Line of Sight Property Sheet Parameters

Object Parameter

Activity

Observer

All the fields in this section except Height are only enabled after the Observer viewpoint is selected in the 3D Window.

X

Enter the X-coordinate for the observer position.

Change this value to move the observer position.

Y

Enter the Y-coordinate for the observer position.

Change this value to move the observer position.

MGRS

The coordinates of the observer position in Military Grid Reference System (MGRS) coordinates. This field is only available if Show MGRS Coordinates was selected in the Options dialog box. SeeView” in the “Using TerraExplorer Options” chapter for more information.

Height

Enter the desired value for the observer altitude.

Targets

All the fields in this section except Height are only enabled after the Target points are selected in the 3D Window.

Selected Point

Select which target point’s position you want to edit.

Target X

The X-coordinate for the target position.

Target Y

The Y-coordinate for the target position.

Target MGRS

The coordinates of the target position in Military Grid Reference System (MGRS) coordinates. This field is only available if Show MGRS Coordinates was selected in the Options dialog box. SeeView” in the “Using TerraExplorer Options” chapter for more information.

Target Height

Enter the desired value for the altitude of the target point (or points).

Analysis

Sampling Interval

Enter the desired value for the resolution of the measurement.

This value represents the distance between sample points along each line. The smaller the sample interval, the more accurate the measurement, but the longer it takes to calculate.

Recalculate

Click this button to perform the calculation again with the updated parameters.

Appearance

Name

Type the description or name of the Line of Sight.

This text appears in the Project Tree as the name of the object.

Activation Action

Select the action to perform when the object is selected from the Project Tree.

Timespan

Start Time

Click Edit and select the date and time when the Line of Sight should first become visible.

End Time

Click Edit and select the date and time when the Line of Sight should stop being visible. 

Visibility

Default Viewing Distance

Determines the viewing distance of the camera from the Line of Sight observer position.

This distance is used as a stop mark for any “Fly-to” or “View Object” operation. It is also used when editing the object from the Project Tree.

When this value is set to the default of -1, TerraExplorer calculates and sets the ideal viewing distance based on its size.

Max. Visibility Distance

Sets the maximal distance from the camera above which the Line of Sight disappears.

Min. Visibility Distance

Sets the minimal distance from the camera below which the Line of Sight disappears.

General

Show in Viewer

Determines if the Line of Sight appears in the Project Tree when the file is viewed with the TerraExplorer Basic viewer.

Message

The message associated with the object. The number displayed is the number of the message.

To create a new message, or update an existing message, open the Create Message dialog box by clicking in this field and selecting Edit. SeeUsing the Create Message Dialog Box” in the “Working with Objects” chapter for more information.

Tooltip

Type a tool tip to appear when the mouse cursor is placed over the Line of Sight in the 3D Window.

Viewshed Tool

The Viewshed tools enable you to calculate the view from a selected observer point or multiple observer viewpoints:

§  3D Viewshed – Calculate and mark all areas on the terrain and on 3D models and objects that are visible from a selected point on the terrain.

§  2D Viewshed - Calculate and mark all areas on the terrain that are visible from a selected point on the terrain.

§  Viewshed Query - Analyzes the visibility of a selected area from multiple viewshed observer viewpoints.

Note:   To display a viewshed analysis from a series of points along a route, use the Viewshed on Route tools. See "Viewshed on Route" in this chapter for information.

The viewshed tool takes into account the viewpoint, direction of sight and distance of sight, when calculating which areas of the terrain are visible from the viewpoint, and which areas cannot be viewed. The viewpoint can be set at any altitude above the terrain.

Creating a 3D Viewshed

The 3D viewshed calculates and marks all areas on the terrain and on 3D models and objects that are visible from a selected point on the terrain.

To create a 3D viewshed:

1.      On the Analysis tab, in the Line of Sight group, click Viewshed. The 3D Viewshed property sheet is displayed.

2.      In the 3D Window, click to define your viewpoint for the 3D viewshed, and then click again to define your desired endpoint (defining the distance of sight).

3.      In the 3D Viewshed property sheet, set the required parameters:

Object Parameter

Activity

Appearance

Name

Type the description or name of the 3D viewshed.

This text appears in the Project Tree as the name of the object.

Visible Area Color

Select the fill color of the areas that are visible from the viewpoint.

Click the Edit button to open the Color dialog box, or type the color code in hexadecimal BBGGRR format (B = Blue channel 00-ff, G = Green channel 00-ff, R = Red channel 00-ff).

Visible Area Opacity

Enter the opacity for the visible area fill.

The opacity is defined as a percentage, where 100% is opaque and 0% is transparent.

Hidden Area Color

Select the fill color of the areas that are not visible from the viewpoint.

Click the Edit button to open the Color dialog box, or type the color code in hexadecimal BBGGRR format (B = Blue channel 00-ff, G = Green channel 00-ff, R = Red channel 00-ff).

Hidden Area Opacity

Enter the opacity for the hidden area fill.

The opacity is defined as a percentage, where 100% is opaque and 0% is transparent.

Border Color

Select the color of the lines that define the boundaries of the viewshed area. Click the Edit button to open the Color dialog box, or type the color code in hexadecimal BBGGRR format (B = Blue channel 00-ff, G = Green channel 00-ff, R = Red channel 00-ff).

Border Opacity

Enter the opacity of the lines that define the boundaries of the viewshed area.

The opacity is defined as a percentage, where 100% is opaque and 0% is transparent.

Viewer Position

Altitude Method

Set the altitude method to be used for the viewer location:

§  Select Relative to Terrain to place the location point at a specified altitude above the ground.

§  Select Absolute to place the location point at a specified altitude above the terrain database vertical datum base ellipsoid.

Altitude

Enter the altitude above the ground for the viewer location.

X

Enter the X-coordinate of the viewer location.

Y

Enter the Y-coordinate of the viewer location.

MGRS

The coordinates of the viewer location in Military Grid Reference System (MGRS) coordinates. This field is only available if Show MGRS Coordinates was selected in the Options dialog box. SeeView” in the “Using TerraExplorer Options” chapter for more information.

Direction

Enter the horizontal angle of the camera when viewing the viewer location.

Pitch

Enter the tilt angle of the viewer position along its lateral axis relative to the horizon.

Settings

Spherical Viewshed

Select Yes to create a full 360 degree sphere.

Horizontal FOV

Enter the horizontal angle limits, in degrees, of the viewshed.

This field is unavailable when the Spherical Viewshed field is set to Yes.

Vertical FOV

Enter the vertical angle limits, in degrees, of the viewshed.

This field is unavailable when the Spherical Viewshed field is set to Yes.

Distance

Enter the length of the viewshed analysis from the viewer in meters.

Quality

Accuracy level of the viewshed calculation.

Refresh Rate

Rate at which the viewshed is recalculated.

Timespan

Start Time

Click Edit and select the date and time when the viewshed should start being visible. 

End Time

Click Edit and select the date and time when the viewshed should stop being visible. 

Visibility

Default Viewing Distance

Determines the viewing distance of the camera from the viewshed.

This distance is used as a stop mark for any “Fly-to” or “View Object” operation. It is also used when selecting to edit the object from the Project Tree.

When this value is set to the default of -1, TerraExplorer calculates and sets the ideal viewing distance for the viewshed based on its size.

Max. Visibility Distance

Sets the distance from the camera at which the viewshed disappears.

Min. Visibility Distance

Sets the minimal distance from the camera below which the viewshed disappears.

General

Show in Viewer

Determines if the viewshed appears in the Project Tree when the file is viewed with the TerraExplorer Basic Viewer.

Message

The message associated with the object. The number displayed is the number of the message.

To create a new message, or update an existing message, open the Create Message dialog box by clicking in this field and selecting Edit. SeeUsing the Create Message Dialog Box” in the “Working with Objects” chapter for more information.

Note:   The message is triggered when the user double-clicks the Project Tree entry that represents the viewshed or clicks the viewshed’s rays in the 3D Window (clicking the hidden/visible areas does not trigger the message).

 

Once completed, the viewshed appears on the terrain as a sector of a circle, where the center point is the viewpoint and the arc is the endpoint (marking the end of the distance of sight analysis), and the 3D Viewshed object appears in the Project Tree. Within the sector, areas that are visible from the viewpoint are colored green (default color), whereas areas that are not visible from the viewpoint are colored red (default color).

 

Creating a 2D Viewshed

The 2D viewshed calculates and marks all areas on the terrain that are visible from a selected point on the terrain.

To create a viewshed:

1.      On the Analysis tab, in the Line of Sight group, click the arrow next to Viewshed, and then click 2D Viewshed.

2.      In the Viewshed Analysis property sheet, set the required parameters:

Table Description automatically generated

Viewshed Analysis Property Sheet

 

Object Parameter

Activity

Settings

Name

Type the description or name of the viewshed.

This text appears in the Project Tree as the name of the object.

Field Of View

Enter a value representing the field of view (the default is 53°).

Ray Spacing

TerraExplorer samples several rays (lines of sight) in the area sector. Type the space between each ray (in degrees). The smaller the ray spacing, the more accurate the measurement, but the longer it takes to calculate.

Max. Sample Interval

Enter the desired value for the sample resolution of your measurement. This value represents the distance between terrain samples for the measurement along each ray. A smaller sample size is more accurate but slower to calculate.

Save Results

Select Yes to create a group in the Project Tree under which the measurement results are saved.

Target Altitude

Enter the required value for the target height.

Viewer Position

Altitude

Enter the altitude above the ground for the viewer location.

X

Enter the X-coordinate of the viewer location (Read-only, derived from the points selected in the 3D Window).

Y

Enter the Y-coordinate of the viewer location (Read-only, derived from the points selected in the 3D Window).

MGRS

The coordinates of the viewer location in Military Grid Reference System (MGRS) coordinates. This field is only available if Show MGRS Coordinates was selected in the Options dialog box. SeeView” in the “Using TerraExplorer Options” chapter for more information.

Direction

Enter the horizontal angle of the camera when viewing the viewer location (Read-only, derived from the points selected in the 3D Window).

Distance

Distance of the viewshed (in meters) (Read-only, derived from the points selected in the 3D Window).

Timespan

Start Time

Click Edit and select the date and time when the viewshed should start being visible. 

End Time

Click Edit and select the date and time when the viewshed should stop being visible. 

 

3.      In the 3D Window, click to define your viewpoint for the measurement, and then click again to define your desired endpoint (defining the distance of sight). The created group is locked and appears as a Viewshed icon in the Project Tree.

Once completed, the viewshed appears on the terrain as a sector of a circle, where the center point is the viewpoint and the arc is the endpoint (marking the end of the distance of sight), and the 2D Viewshed object appears in the Project Tree. Within the sector, areas that are visible from the viewpoint are colored green, whereas areas that are not visible from the viewpoint are colored red.

Viewshed Query

The Viewshed Query tool enables you to analyze the visibility from multiple viewshed observer viewpoints to a selected area. Based on the 3D viewshed analysis object, the tool computes the overall visibility of different points in the designated area. The output of the analysis is exported to a point shapefile that graphically represents the visibility of the different points. Two color schemes are available; one scheme only distinguishes between visible (green) and invisible (red), while the other one color codes the points according to their visibility percentage:

§  Green = More than 80% of the selected viewsheds’ observer viewpoints are visible from this point.

§  Yellow = 50 - 80% of the selected viewsheds’ observer viewpoints are visible from this point.

§  Orange = 0-50% of the selected viewsheds’ observer viewpoints are visible from this point.

§  Red = 0% of the selected viewsheds’ observer viewpoints are visible from this point.

 

To use the Viewshed Query tool:

1.      On the Analysis tab, in the Line of Sight group, click the arrow next to Viewshed, and then click 3D Viewshed Query. The Viewshed Query dialog box is displayed.

Graphical user interface, application Description automatically generated 

Viewshed Query

2.      Select one of the Create as options:

Option

Description

Layer (Entire)

Create a feature layer under the application’s AppData.

Layer (Streaming)

Create a streaming feature layer under the application’s AppData.

3.       Enter the following parameters:

Parameter

Description

Query

The list displays all 3D viewsheds in the project. Only selected 3D viewsheds are taken into account when calculating the ratio between visible and invisible viewsheds. Click the required viewshed(s). Use CTRL-click or SHIFT-click to multi-select.

Click Refresh list to update this list to the current project status.

Out of Range

Defines how to handle query points that are outside of the calculated areas of all selected 3D viewsheds. Select either:

§  Ignore Point - Do not add points outside of the range of any selected 3D viewshed.

§  Add Point - Add points outside of the range of any selected 3D viewshed. These query points are considered to have 0% visibility and color coded in red.

Color Scheme

Defines the color coding scheme of the output points. Select either red | green or red | orange | yellow | green.

Spacing

Determines the horizontal and vertical spacing (in meters) between query points in the area for which the viewshed query is being calculated. The spacing property also defines the scale of the output points.

Min Altitude

Defines the altitude above ground level of the closest point to the ground.

Max Altitude

Defines the maximum altitude above ground level. If the Max Altitude is higher than the Min Altitude, the 3D Viewshed Query tool generates a matrix of points according to the Spacing value.

4.      Select one of the following methods of designating the area for which the viewshed should be calculated:

§  Follow Line – Query points are created along the drawn line. In the 3D Window, left-click to place the line waypoints, and right-click to complete the line.

§  Fill Area – Query points are created inside the drawn polygon.

§  Selected Group – Query points are created at all points, along all lines, or inside all polygons, in the selected feature layer. Select the required layer from the Project Tree, and then click Selected Group.

§  From Clipboard - Query points are created at all clipboard objects.  

§  Viewshed Area - Query points are created exactly in the area of the selected 3D viewsheds.

Viewshed on Route Tool

The Viewshed on Route tools provide you with a graphical representation of the view on the terrain from a series of points (route):

§  3D Viewshed on Route by Speed – Provides an animated representation of the terrain and objects that are visible as a dynamic object progresses along a defined route according to a set speed.

§  3D Viewshed on Route by Time – Provides an animated representation of the terrain and objects that are visible as a dynamic object progresses along a defined route over a defined time frame.

§  3D Viewshed on Route Query– Analyzes the visibility of a selected area from multiple viewshed observer viewpoints along a route.

§  2D Viewshed on Route - Provides an animated representation of the terrain that is visible as a dynamic object progresses along a defined route

Note:    When calculating the viewshed from a route, the field of view is automatically set to 360°.

Creating a 3D Viewshed on Route – By Speed

The 3D viewshed on route – by speed provides an animated representation of the terrain and objects that are visible as a dynamic object progresses along a defined route according to a set speed. 

To create a viewshed from a route – by speed:

1.      On the Analysis tab, in the Line of Sight group, click the arrow next to Viewshed on Route, and then click 3D Viewshed on Route – By Speed.

The 3D Viewshed on Route property sheet is displayed.

3dviewshedonroutebyspeed.gif

Viewshed on Route – By Speed Dialog Box

2.      In the Viewshed on Route dialog box, set the required parameters:

Property

Description

Model Type

Graphic representation of the dynamic object. Select one of the 3D models: Car, Humvee or Tank, Icon for a 2D image icon, or Empty for no graphic representation.

Speed

Speed of the dynamic object in mph or km/h.

Loop

Defines whether the dynamic object stops at the end of the path or loops back to the beginning.

Viewer Height

Altitude of your viewpoints.

Viewshed Distance

Distance of the 3D viewshed (in meters).

Spherical Viewshed

Select Yes to create a full 360 degree sphere.

Color Scheme

Select the colors that will represent the visible and non-visible areas from the viewshed.

Clipboard

Viewpoints are created at all clipboard objects.

3.      Once you have set the necessary parameters, click in the 3D Window to define the first waypoint on your route. Drag and click the mouse to define the route’s other waypoints. Right-click to finish. The Dynamic 3D Viewshed group appears in the Project Tree. As the dynamic object moves along the defined route according to the set speed, the viewshed dynamically changes providing an animated representation of the terrain and objects that are visible from each point on the route.

Creating a 3D Viewshed on Route – By Time

The 3D viewshed on route – by time calculates and dynamically marks the terrain and objects that are visible from an object as it moves along a defined route over the course of a set time frame. 

To create a viewshed from a route – by time:

1.      On the Analysis tab, in the Line of Sight group, click the arrow next to Viewshed on Route, and then click 3D Viewshed on Route – By Time. The 3D Viewshed on Route property sheet is displayed.

3dviewshedonroutebytime.gif 

Viewshed on Route – By Time Dialog Box

2.      In the Viewshed on Route dialog box, set the required parameters:

Property

Description

Model Type

Graphic representation of the dynamic object. Select one of the 3D models: Car, Humvee or Tank, Icon for a 2D image icon, or Empty for no graphic representation.

Start Time

The time the dynamic object begins moving along the defined route.

The date and time slider automatically adjusts to correspond to the timespan defined by the Start Time and End Time.

End Time

The time the dynamic object reaches the end of the defined route.

Viewer Height

Altitude of your viewpoints.

Viewshed Distance

Distance of the 3D viewshed (in meters).

Spherical Viewshed

Select Yes to create a full 360 degree sphere.

Color Scheme

Select the colors that will represent the visible and non-visible areas from the viewshed.

Clipboard

Viewpoints are created at all clipboard objects.

3.      Once you have set the necessary parameters, click in the 3D Window to define the first waypoint on your route. Drag and click the mouse to define the route’s other waypoints. Right-click to finish. The created 3D Viewshed on Route group appears in the Project Tree. When the time and date are adjusted in the Time and Date slider and the dynamic object moves along the defined route, the viewshed dynamically changes, providing a representation of the terrain and objects that are visible from each point on the route.

Querying a 3D Viewshed on Route

The Viewshed Query tool enables you to analyze the visibility from multiple viewshed observer viewpoints along a route to a selected area. Based on the 3D viewshed analysis object, the tool computes the overall visibility of different points in the designated area. The output of the analysis is exported to a point shapefile that graphically represents the visibility of the different points. Two color schemes are available; one scheme only distinguishes between visible (green) and invisible (red), while the other one color codes the points according to their visibility percentage:

§  Green = More than 80% of the route’s viewpoints are visible from this point.

§  Yellow = 50 - 80% of the route’s viewpoints are visible from this point.

§  Orange = 0-50% of the route’s viewpoints are visible from this point.

§  Red = 0% of the route’s viewpoints are visible from this point.

 

To create a 3D viewshed on route – query:

1.      On the Analysis tab, in the Line of Sight group, click the arrow next to Viewshed on Route, and then click 3D Viewshed on Route – Query. The 3D Viewshed on Route property sheet is displayed.

 

3dviewshedonroutebyquery.gif

Viewshed on Route – Query Dialog Box

2.      In the Viewshed on Route dialog box, set the required parameters:

Property

Description

Viewshed Interval

The distance between terrain samples for the measurement along each ray. A smaller sample size is more accurate but slower to calculate.

Viewer Height

Altitude of your viewpoints.

Viewshed Distance

Distance of the 3D viewshed (in meters).

Spherical Viewshed

Select Yes to create a full 360 degree sphere.

Quality

Accuracy level of the viewshed calculation.

Min Altitude

Defines the altitude above ground level of the closest point to the ground.

Max Altitude

Defines the maximum altitude above ground level. If the Max Altitude is higher than the Min Altitude, the 3D Viewshed Query tool generates a matrix of points according to the Spacing value.

Spacing

Determines the horizontal and vertical spacing (in meters) between query points in the area for which the viewshed query is being calculated. The spacing property also defines the scale of the output points.

Clipboard

Viewpoints are created at all clipboard objects.

3.      Once you have set the necessary parameters, click in the 3D Window to define the first waypoint on your route. Drag and click the mouse to define the route’s other waypoints. Right-click to finish. The output of the analysis is exported to a point feature layer that graphically represents the visibility of the different points.

4.      In the 3D Window, click any of the route’s Indicator  icons to toggle display of the viewshed from that individual point.

Creating a 2D Viewshed on Route

The 2D Viewshed on Route calculates the terrain that is visible as a dynamic object progresses along a defined route.

There are three options for displaying the calculated route viewshed: 

§  Individual viewshed results for each selected point along the route

§  A series of individual viewshed results that display according to a set timespan

§  A single composite viewshed showing visible area from any of the route’s waypoints

Note:    When calculating the viewshed from a route, the field of view is automatically set to 360°.

To create a viewshed from a route:

1.      On the Analysis tab, in the Line of Sight group, click the arrow next to Viewshed on Route, and then click 2D Viewshed on Route:

The Viewshed on Route property sheet is displayed.

Table Description automatically generated

Viewshed on Route Property Sheet

2.      In the Viewshed Analysis property sheet, set the required parameters:

Property

Description

Name

Type the description or name of the viewshed.

This text appears in the Project Tree as the name of the object.

Ray Spacing

Determines the horizontal and vertical spacing (in meters) between each ray (in degrees). The smaller the ray spacing, the more accurate the measurement, but the longer it takes to calculate.

Max. Sample Interval

The distance between terrain samples for the measurement along each ray. A smaller sample size is more accurate but slower to calculate.

Distance

Length of the 3D viewshed from the viewer (in meters).

Viewer Height

Altitude of your viewpoints.

Analysis Type

Select one of the options for displaying the viewshed:

§  Viewshed on Route: Individual viewshed results for each selected point along the route. Each circle has a radius equal to the Distance of Sight.

§  Timespan Viewshed on Route: A series of individual viewshed results that display according to a set timespan

§  Cumulative Viewshed on Route: A single composite viewshed showing visible area from any of the route’s waypoints

Start Time

The time the dynamic object begins moving along the defined route.

The date and time slider automatically adjusts to correspond to the timespan defined by the Start Time and End Time.

End Time

The time the dynamic object reaches the end of the defined route.

Dist. Between Waypoints

Distance between sample route waypoints.

 

3.      Once you have set the necessary parameters, click in the 3D Window to define the first waypoint on your route. Drag and click the mouse to define the route’s other waypoints. Right-click to finish.

Note:       While creating the route, the Dist. Between Waypoints property is still editable.

4.      Click Calculate. The created Viewshed on Route locked group appears in the Project Tree.

5.      Once you establish the endpoint, all the parameters become read-only. At this point, TerraExplorer Pro begins to calculate the viewshed measurement. This process can take some time if the route has a considerable number of waypoints.

Threat Dome Tool

The threat dome tool analyzes and displays the area that is visible from a given point on the terrain within a 360° horizontal field of view. Several display options for the threat dome are available so that the particular information required can be easily visualized. The threat dome can be generated as a dome that defines the outer boundaries of the volume that is visible from the viewpoint, as a dome base that divides between visible and non-visible areas, or alternatively as a skyline that highlights obstructions to the field of view. After generating the threat dome, results can be further analyzed by creating a profile graph.

Using the Threat Dome Tool

To use the threat dome tool:

1.      On the Analysis tab, in the Terrain Analysis group, click Threat Dome. The Threat Dome dialog box is displayed.

A screenshot of a cell phone Description generated with very high confidence

Threat Dome

2.      Set the Threat Dome properties:

Property

Description

Type

Output of the tool. Select one of the options for representing the visible area from the threat point:

§  Dome – A spherical dome is generated that encloses all points that can be viewed from the dome’s viewpoint.

§  Dome base – A 2D circular surface is generated defining the area below which all points are not visible from the dome's viewpoint. 

§  Skyline – An outline of the visible terrain and objects is generated, highlighting any objects (e.g., buildings or mountains) that block the viewpoint's field of view. 

Quality

Determines the distance between sample points by which the threat dome is being calculated. High Quality will yield a more accurate result, but take longer to calculate.

Radius

Radius of the threat dome.

Viewer Altitude

Altitude above the ground for the viewer location.

Elevation Angle

Enter the angle, from the ground, below which the viewpoint cannot see. For example, an elevation angle of zero creates a complete half sphere (or base of a half sphere if Type is set to Dome base), whereas an angle of 30 degrees creates an inverted cone, topped by a section of a sphere (or just an inverted cone if Type is set to Dome base).

Note:    This field is not available if Type is set to Skyline.

3.      Select one of the following methods of designating the area for which the threat dome should be calculated. If the input group contains multiple points, then individual threat domes are generated for each of the points

§  Set Position – Click in the desired location for the threat dome query. A marker marker2.gif is created at the drawn point.

§  Selected Group - Query points are created at all point elements (point features or point objects) in the selected group. Select the required group from the Project Tree, and then click Selected Group. A separate threat dome is created for each of the point elements, with the center of each threat dome indicated by a different color marker.

§  From Clipboard - Query points are created for all point elements in the clipboard. Copy the required elements to the clipboard, and click From Clipboard.

The created Threat Dome group appears in the Threat Dome group in the Project Tree. The created group includes a Dome polygon object, a Viewer image label representing the viewpoint, and a Ring polyline representing the perimeter of the volume that is visible from the viewpoint. You can open any of their property sheets to further control the way the threat dome object is displayed. See "Polygon Property Sheet Parameters", "Polyline Property Sheet Parameters", and "Image Label Property Sheet Parameters" in the "Objects and Labels" chapter for more information.

4.      If you want to display a graph of the threat dome profile for the last created threat dome, click Show Profile. Note that if the input group contains multiple points, the color of each profile line on the Dome Ring Profile graph matches the color of the corresponding threat dome's query point marker in the 3D Window.

Note:       The Show Profile button is only displayed after a threat dome is created.

A threat dome profile graph opens, displaying the terrain elevation profile.

domeprofile.gif

Threat Dome Profile Graph

5.      Use the Zoom in zoomin.gif, Zoom out zoomout.gif, and Zoom to full extent of data zoomextent.gif buttons to adjust the zoom as required.

6.      Determine what information is indicated on the graph by selecting any of the following display options:

Waypoint

Select the check box to mark the waypoints on the graph with a .

Min/Max Elevation

Select the check box to mark the maximum and minimum points with a .

Min/Max Slope

Select the check box to mark the maximum and minimum slope with a .

7.      If you want to export the threat dome profile to a shapefile layer, click Export to Layer.

Note:       When a threat dome profile is exported to a layer, the line color on the graph corresponds to the color of the points that make up the line in the layer.

8.      Point to any point on the graph to display the following values. If you want to display the values and also jump to the point on the terrain, then click instead of pointing.

Value

Description

X

X-coordinate of the selected point.

Y

Y-coordinate of the selected point.

Elevation

Elevation value of the point above the terrain database vertical datum base ellipsoid.

Slope

Slope of the curve at the selected point

 

Buffer Query Tool

The Buffer Query tool detects all penetrations by 3D elements (e.g., 3D object or 3DML) to a set buffer zone of a selected polyline. This can be used, for example, in implementing safety requirements related to safe distances from a power line. The tool scans the buffer zone of each of the polyline's query points, and colors in red all query points with breached buffer zones. Clicking this query point highlights in red the 3D element that was found.

The output of the analysis is a point feature layer that graphically represents the locations along the line where a penetration to the buffer zone was found.

To use the Buffer Query tool:

1.      On the Analysis tab, in the Line of Sight group, click Buffer Query. The Buffer Query dialog box is displayed.

A screenshot of a cell phone Description generated with very high confidence

Buffer Query

2.      Set the scan properties:

Buffer Radius

Radius of the buffer zone (in meters) from each of the polyline's query points

Min Distance

Minimum distance (in meters) from the polyline for inclusion in the buffer zone.

Scanning Area

The area to be scanned. Select Above query point (180°) to limit the scan to the FOV above the query point. Select Above & sides below (270°) to skip only the FOV directly below the query point.

3.      Select one of the following methods for selecting the polylines for the buffer query. If the input group contains multiple polylines, each one is scanned, and the results collected in a in a single result layer

§  Selected Group - Buffer scans are performed for all polylines in the selected group or layer. The required Project Tree group must be selected before selecting this option.

§  From Clipboard - Buffer scans are performed for all polylines on the clipboard. The polylines must be on the clipboard before selecting this option.

4.      Review the buffer query results. All query points in whose buffer zone one or more 3D elements were found are colored in red. Click a red query point to highlight in red the 3D elements that were found. Click the point again to toggle off that query point's highlighting. Click the Clear button to clear all highlighting from any query point.

5.      The buffer query results are automatically exported to a point shapefile that is listed in the Project Tree and saved under the application AppData. You can find the full path to this shapefile in the layer's property sheet, in the File Name property under the Layer tab.