As you can see, I’m just skipping along from product to product and topic to topic. I know it may seem inefficient, but for me, it’s important to get a feeling of what ideas and technologies are the ones that connect these products and services together. To me, it’s too early to hunker down and start working too deeply… not until I can get a better sense of what my learning path should be.
So today I’m working through the introductory chapters of Mapping With Drupal. And in these chapters I learned about Tile Compare : a tool by the author that gives a side-by-side comparison of the tiles of Google, Bing, Yahoo (man, if I sometimes forget about Bing, I *always* forget about Yahoo), and Open StreetMap.
Speaking of introductory chapters to mapping, I really enjoyed MapBox’s How Web Maps Work, which explains the concepts behind tiles and zooming their naming conventions and how they related to each other:
Zoom levels are related to each other by powers of four – z0 contains 1 tile, z1 contains 4 tiles, z2 contains 16, and so on. Because of this exponential relationship the amount of detail increases at every zoom level but so does the amount of bandwidth and storage required to serve up tiles. For example, a map at z15 – about when city building footprints first become visible – requires about 1.1 billion tiles to cover the entire world. At z17, just two zoom levels greater, the world requires 17 billion tiles.
I’d recommend firing up Tile Compare and zoom out until you reach z0 (you can see the entire world) and then continue to zoom in. Here are some of the observations I made as I did this:
- Google and Yahoo default to coloured themes that express elevation, whereas Bing and OpenStreetMap opt for a whiter background (although Bing does express some elevation differences with grey shading)
- rivers seem over exaggerated in Yahoo maps – you can see them appear prominently at zoom level 3
- at level 4, the highways seems appear and in the case of Yahoo especially, they bring to mind an image of varicose veins
- I love the typography of the Bing Maps the best. I’ve noticed that unlike the others, they’ve opted to mark state borders with straight lines, for a cleaner visual appears, I’d suspect.
- OpenStreetMaps labels are disappointingly pale and emerge at later levels than its peers. At level 5, the labels of Windsor and Warren are visible but not Detroit
The more I compare the appearance of these maps, the more I like Bing Maps!