G'day Bidgee and Dlinth, firstly let me reveal my interests and just say I am a sandgroper, but I am also a Wikipedian with a commitment to order and integrity.  I had earlier thought that Perth was the most isolated city in the world with a population over a million (with the closest city of comparable size being Surabaya or Jakarta).  In fact neither fact was true, which I confirmed by using the online GIS application Mapcrow.  I believe that using the same GIS application should confirm distances and any comparisions between different pairs of cities.