Google introduced Google Maps 5.0 for Android with two significant new features: 3D interaction and offline reliability. In order to create these features, Google rebuilt Maps using vector graphics to dynamically draw the map as you use it.
How maps were created before?
Previously, Google Maps downloaded the map as sets of individual 256×256 pixel “image tiles.” Each pre-rendered image tile was downloaded with its own section of map imagery, roads, labels and other features baked right in. Google Maps would download each tile as you needed it and then stitch sets together to form the map you see. It takes more than 360 billion tiles to cover the whole world at 20 zoom levels!
Now, Google uses vector graphics to dynamically draw the map. Maps will download “vector tiles” that describe the underlying geometry of the map. You can think of them as the blueprints needed to draw a map, instead of static map images. Because you only need to download the blueprints, the amount of data needed to draw maps from vector tiles is drastically less than when downloading pre-rendered image tiles.
Vector graphics also enable another significant new feature: the ability to continue viewing maps even when you have poor—or no—network connections. Because each vector tile works across multiple zoom levels, it requires more than 100 times less data to view maps across all zoom levels than before, allowing Maps to cache much larger areas of the map on your device.