TomSym CCTV Surveillance

This page is part of the TomSym Manual. See TomSym Manual.

Problem description

In the course of the last few months, the industrial zone of Billston has suffered from a series of break-ins and thefts during the night. The zone is watched by security men but there are too few of them. The town council in charge of security in this zone decides to install surveillance cameras to aid the security men with their task. These cameras can be directed and pivot through 360 degrees. By installing a camera at the intersection of several streets, it is possible to survey all adjoining streets. The map in the figure below shows the industrial zone with the limits of the zone to be covered by closed circuit TV (CCTV) surveillance and the 49 possible locations where to install the cameras. What is the minimum number of cameras that have to be installed to survey all the streets of this zone and where should they be placed?

The industrial zone in Billston

13 -- 14 -- 18 -- 17    28 -- 29    35 -- 36

|     |     |           |           |
 |     |     |           |           |
 |
 |    15 -- 19          26 -- 27    34    48
 |
 |  /  |     |           |           |     |
 | /   |     |           |           |     |

12    16 -- 20    24 -- 25 -- 30    33    47 -- 45 -- 46

|  /        |        /        |  /  |           |
 | /         |       /         | /   |           |

3 -- 11 -- 21 -- 22          31    37 -- 43 -- 44 -- 49

| \                 \         |     |
 |  \                 \        |     |
 |
 |    4 -- 9 -- 10      23 -- 32 -- 38
 |
 |    | \                      |     |
 |    |  \                     |     |
 |
 |    6     5                 39 -- 40 -- 41 -- 42
 |
 |    | \                      |        /
 |    |  \                     |       /
 |                             |      /
 |    8     7                  |     /
 |                             |    /
 |                             |   /
 |                             |  /
 |                             | /

1 --------------------------- 2

Variables

arcs_out/in                These variables describe the network
                           of streets

Reference

Applications of optimization... Gueret, Prins, Seveaux

% Marcus Edvall, Tomlab Optimization Inc, E-mail: tomlab@tomopt.com
% Copyright (c) 2005-2009 by Tomlab Optimization Inc., $Release: 7.2.0$
% Written Oct 7, 2005.   Last modified Mar 24, 2009.

Problem setup

arcs_in =  [1 1 2 2 3 3 3 3 4 4 4 6 6 9 11 12 12 13 14 14 15 15 16 ...
    17 18 19 20 21 22 22 23 24 25 25 26 26 28 30 31 31 32 32 ...
    33 33 34 35 37 37 38 39 40 41 43 44 44 45 45 47]';

arcs_out = [2 3 39 41 4 11 12 16 5 6 9 7 8 10 21 13 15 14 15 18 16 ...
    19 20 18 19 20 21 22 23 25 32 25 26 30 27 28 29 31 32 33 ...
    38 39 34 37 35 36 38 43 40 40 41 42 44 49 45 46 47 48]';

n = length(arcs_in);  %arcs
arcs = tom('arcs',n,1,'int');

% All variables are binary
bnds = {0 <= arcs <= 1};

% All streets need to be covered
con = {arcs(arcs_in) + arcs(arcs_out) >= 1};

% Objective
objective = sum(arcs);
constraints = {bnds, con};
options = struct;
options.solver = 'cplex';
options.name   = 'CCTV Surveillance';
sol = ezsolve(objective,constraints,[],options);

PriLev = 1;
if PriLev > 0
    disp('Put cameras in nodes ')
    disp(num2str(find(sol.arcs)'))
end

% MODIFICATION LOG
%
% 051205 med   Created
% 060118 per   Added documentation
% 060125 per   Moved disp to end
% 090325 med   Converted to tomSym

Problem type appears to be: mip
Time for symbolic processing: 0.0099015 seconds
Starting numeric solver
===== * * * =================================================================== * * *
TOMLAB - TOMLAB Development license  999007. Valid to 2011-12-31
=====================================================================================
Problem: ---  1: CCTV Surveillance              f_k      24.000000000000000000
                                              f(x_0)      0.000000000000000000

Solver: CPLEX.  EXIT=0.  INFORM=101.
CPLEX Branch-and-Cut MIP solver
Optimal integer solution found

FuncEv   23 
Elapsed time: 0.002000 sec. 
Put cameras in nodes 
2   3   4   6   9  13  15  18  20  21  23  25  26  28  31  33  35  37  38  39  41  44  45  47