Due to space limitations the method to compute the routes can only be sketched here. The full method has been
published in (Kretz, Lehmann, & Hofsäss, 2014). We also refer to that paper for an extensive overview and discussion
of previous relevant work.
As a first step a map of distances to destination is computed. In this map certain ranges of distance (for example
each 2 meters) are combined to areas. The extent of this combination (2 or 5 or 10 meters) is a parameter of the
method. The larger the value of this parameter is, the less alternatives will be found. A routing alternative is then
found if there are two or more unconnected areas which have the same distance to destination. Figure 5 visualizes this
idea. Once a routing alternative has been found one intermediate destination is created for each alternative. This
process has to be repeated iteratively for each newly found intermediate destination until the entire walking area or at
least all input areas are covered in an iteration step which does not bring up another routing alternative