Geographically challenged

Melbourne is dead easy to navigate.  Unlike Sydney, it's built on a grid system, with all roads going North to South or East to West.  It's because it's dead flat, which adds to the ease of lifestyle.  Check it out here:

So apart from the Nepean Highway cutting a swathe across the middle, it's dead straight forward.  So this morning I decided to run from McKinnon to the beach (due West), along the bay a bit (I can't call it a beach being from Manly) and then back home.  All went well, running parallel to North Rd and reaching the bay in perfect early morning weather.  Then I ran back, heading due East.  Except, after an hour, I find myself in a suburb I didn't recognise (Hampton - which was very nice).  So I panicked a bit and ran more directly home, except I then end up in Sandringham. Which is by the Bay even further away.  So having been out for 1 hour and 15 and miles from home with no idea how to get back, I did a Rob Costello and caught a taxi.

Take a look at the map again.  It's all NSWE grid lines apart from a random section in Brighton which looks like a fault line or earthquake has hit it.  That was my problem.

15km, probably.