In order to make more realistic simulations, the length and elevation
profile of a BRouter route can be imported. For this, the URL parameter
"brouter" is set to a BRouter URL; its parameters are extracted, and
during startup the corresponding route data is downloaded from
brouter.de.

Because Javascript code cannot exchange data from arbitrary servers, the
relevant code is written in PHP; thus, the Javascript remains the same,
with or without BRouter data.