OpenStreetMap, an open source compeditor to Google Maps does a similar 'split the word into tiles'. This is how they do it:
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.
How did you come up with that number? The sum loop that follows reports 524287 tiles total.
#include <stdio.h> #include <math.h> int main(void) { int i; double tot = 0; for(i = 0; i <= 18; ++i) tot += exp2(i); printf("tot %f\n", tot); return 0; }
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.