Sensor Placement and Coverage

If you check Options, Menus tab, Show labs:

• Go to Files, GIS Labs, Sensor coverage

Otherwise

• Download data files for Sensor Placement Exercise at http://www.usna.edu/Users/oceano/pguth/downloads/sensor_placement_lab.zip. 

 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:

• Word document with maps showing your coverage, and a printout of the results, for three different arrangements of 5 sensors selected from your 10.  Include a discussing of:

  • Which part of the area is causing you the most problems, and why.
  • How hard you think it will be to get multiple coverage of the border with this sensor density.
  • Do you think the landcover categories along the border will impact the ability of the sensors to work.  You have an NLCD landcover data set to go with the DEM.
  • We are using a 1" DEM.  What would change if we used the 1/3" DEM which is also available?
  • What principles you think you should use to place sensors.
• The dBase table with your sensor locations.  This will be the "unfiltered" version, with all 10 locations, with the 5 used in your best solution indicated in the USE field.

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:

• Set the parameters given above for each sensor in the Viewshed parameters window.   This is especially important for the first sensor, since the settings will be remembered for the others. Set the horizontal viewport with the left and right boundaries, and the vertical viewport with the min and max inclinations, and minimum and maximum ranges.

• If you fans are not showing check:

  • That the vertical viewport is reasonable.  If you place sensors on tall platforms on hilltops, they might have to be aimed downward.
  • That the Opacity of the fans is not set to 0.

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,

• Right click on the map and pick "Edit fans", which brings up a fan edit window which gives some analysis options.
• Save the sensor locations with Report, DBF on the fan edit window.  The default location will be cleared when you close the program.
• Restore the sensor locations with File, Load Weapons with the map window active.  This allows the locations and any changes to be saved between times you run the program.

The key options:

• Compute fan coverage  gives the location and characteristics of the sensors, and the coverage computations of the target shapefile.
• Pick sensors:  turns individual sensors on and off.

last revision 4/18/2017

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