Sensor Placement and Coverage

If you check Options, Menus tab, Show labs:


 This gives you a DEM and the NLCD for a location on the Arizona border, in the region where DHS had a large demonstration project called P28 which was part of the Secure Border Initiative (SBInet)

The diagonal green line is the border which we want to cover with sensors, represented by a thin shapefile.

The locations of 6 sensors and their Viewsheds are also shown.

We will calculate the sensor coverage by the percentage of  the border shapefile that is in the the visible portion of the viewsheds  for the sensors.

Turn in:


You will use sensors with the following characteristics, set on the Viewshed Parameters window.  The size of the towers matches news reports, but the characteristics of the sensors (radar, infrared and other according to the news reports) are hypothetical.

  • Range 500-10,000 meter.  Sensors cannot operate close to the tower.
  • Height 30 m above the ground
  • Target height 2 m above the ground
  • Horizontal field of view: 60˚.  The coverage starts with the left boundary, and goes to the right boundary.  Note that the left and right boundaries are adjusted to get this width, and the sensors are aimed to the SW because of the orientation of the border.  This could be adjusted.
  • Vertical field of view: 20˚.  Note that the Max and min inclination are adjusted, and the aiming point is at -5˚ since the towers are tall and will be placed on high terrain.

By default, the program will save the viewsheds in c:\mapdata\temp, which will be cleaned out when you close the program.  You might want to change that location, with the Path button on the bottom of the form, to the directory you are using for the lab.  The program can regenerate the fans if you save the sensor locations, but you can can save some time by saving the viewsheds in a safe location.

New DEM and load the DEM and NLCD.  Locate the international border.  You can note this as an artefact in the DEM, or overlay the state or county borders on the map.  You can also look at the NLCD, and note the change in coverage at the border.  You probably want a grayscale reflectance map.

Annotate Map, Create shapefiles, to create an area shapefile for the international border.  You are creating a small area that covers the border so that you can determine the effectiveness of  sensor placement.   Insure that the shape file plots with a solid fill pattern (Symbol and color selection).  Fan coverage computations will do an intersection of this region with the fan coverage.

1:1 map view (best resolution view of the data, and best chance to get optimal sensor placement)

Go to the Coordinates  tab on the Options form, and pick Reasonable for "Verify graphical selection", and "Graphical blowup" for the Verify option.   Graphical selection might not be very precise, and could place sensors in holes from which they might not see very much.  If you know coordinates, perhaps from a GPS field survey, you could pick the option to type them in from the keyboard.

Weapons fan/viewshed.  Place at least 10 sensors to attempt to cover the border.  Insure that you correctly:

Map Overlays  Adjust the order of overlays, plotting the Sensor fans after the Database with the border. 
Check the opacity, set with the slider on the Sensor panel; Pick a midrange opacity for the fans, which will let you see the terrain behind the fans..

After you have entered the sensors,

The key options:

last revision 4/18/2017