Sure there are lots of little tools on the net for measuring the driving distance using asphalt roads, but sitting here trying to figure out if I can make a walk from Ans to Kongensbro along Tange sø and Gudenåen and if I shold take the bus back to Ans when I get to Kongensbro or walk back again, these tools were pretty useless.
That is when I realized that google maps is perfect for this, someone must have build something to measure distances along a chosen path. I am sure there are other tools out there but this one solved my need.
The distance from Ans to Kongensbro should be something like 7 km. along the water so I should be able to walk out and back home before the sun sets if I get out the door now. ... which means I should stop writing and get moving :)