Introduction
Constraint Based Geolocation (CBG) technique takes multiple landmarks as input to plot circles and identify possible regions of intersection of these circles. CBG technique uses its algorithm to convert delay to distance before plotting the circles. We modified CBG to produce a separate output file in the following format for each target. Each line indicates a different landmark with its latitude, longitude and distance from target. These values are separated by white-space. It is important to mention here that landmarks for each target were sorted beforehand on the basis of delay. Moreover landmarks with erroneous delay measurements were eliminated. This is done to consider those landmarks that are closer to a target in order to calculate a better estimate position for a target.
landmark1-latitude landmark1-longitude distance1 landmark2-latitude landmark2-longitude distance2 landmark3-latitude landmark3-longitude distance3
We then feed the above file as input to Apollonius algorithm. This format is compatible to Apollonius since it requires the input in the following format for three circles per target. The pair (x, y) indicates the center of a circle, therefore a (lat, long) pair translates into an (x, y) pair. Similarly distance from a CBG .lnd file is same as radius.
x1 y1 radius1 x2 y2 radius2 x3 y3 radius3
Apollonius algorithm performs calculations and outputs the following for each target. Each line indicates estimations for each target.
target-IP actual-lat actual-long estimated-lat estimated-long error-distance