Our next rev of the mapping software included tiling and progressive tile loading. We started with a commercial backend for creating the tiles (ESRI ArcIMS), and eventually switched to an open source solution (UWM's MapServer). Last I heard they had an entirely open source stack (MapServer, OpenLayers, gdal, etc).
Anyways, when I realized that Google had cached each and every one of these tiles - at every zoom level - I was simply confounded. It was the first time I actually contemplated the scale of a company like Google.
The problem back then was storage. Even for the US-only trail maps we were doing, there was no way we were going to store all those tiles at the $$$/GB that hard-drive space went for at the time. The plan was to cache only the most popular areas, and rebuild outlying tiles as necessary.
http://mathworld.wolfram.com/MillerCylindricalProjection.htm...
Here's an excerpt (given that Google tiles are 256x256 and at zoom 0 one tile covers the whole world):
"Intuitively its easy to see why the scale changes. Let's think about Google Maps zoom level 0. At zoom level 0 the world is fit into a 256 pixel wide image. But we know that the earth's circumference is the largest at the equator and dwindles down to zero at the poles. So as you move north or south away from the equator, the Earth has to be "stretched" to fit into the 256 wide bitmap. Thus as you move north or south the scale gets larger and larger because the same number of pixels on the screen are showing you a larger and larger percentage of the Earth's surface."
The Google LatLong blog (http://google-latlong.blogspot.com/) is packed with information related to Google Maps, and the maps API Google Group also is.
There's lots of talk about the Mercator projection on the list, tradeoffs, pros, cons, etc. So there really was no need to read the obfuscated code. Also, I'm not sure if "ease of implementation" was really what had them choose this projection, so it wouldn't hurt to dig around a little bit more before saying stuff like that, I think.
Still, pretty good stuff for people that want to know a bit more about how Google Maps work.
I don't know how much information was available at that time but it shouldn't be much.
If you have a garmin GPS you can download the garmin map files based on OSM for your gps from this site http://download.geofabrik.de/osm/ . You can also get navit files from OSM which works on the open source navit satnav programme. Neither of those are browser based tiles though.
In other words if you look through the details of projection and coordinate systems the spacial partitioning scheme used is the familiar BSP tree.
I'm going to remember this the next time someone tries to tell me they can't handle large open areas effectively... "what, you mean like THE WHOLE PLANET!!111 lolz"
:D
If you've ever done any OpenGL programming, you know that the bottom left of the screen is considered the origin
