Without a clear purpose, your map runs the risk of confusing people who you'd like to communicate with. Paul Farrell and Richard Bentley discuss why a map needs a purpose and how you know you've got one. They also give examples of their favourite purposeful maps. http://stuffin.space (Stuff in Space - 3D map of space junk) http://www.coastalrisk.com.au (Coastal Risk Australia) https://itunes.apple.com/au/app/skyview-explore-the-universe/id404990064?mt=8 (Skyview app iOS) https://play.google.com/store/apps/details?id=com.t11.skyview (Skyview app Android)