The Google Map system is based on the World Mercator projection which makes latitude and longitude lines parallel and perpendicular to each other. This is just one of a number of flawed ways to depict a sphere as a flat surface. It falls apart when looking at latitudes above about 85 degrees (plus or minus) as the distance between longitude lines converge.
As for a grid, the latitude and longitude lines themselves form a grid due to the way World Mercator is projected. You can use straight coordinates to form your grid. The zoom system is based on the idea that the entire world fits in one 256x256 pixel image at zoom level zero, then divides that into 4 cells at zoom 1, 16 at zoom 2, etc. Each successive zoom multiplies the number of tiles (or cells) by 4. Following this presentation should give you a pretty good idea on how the system functions exactly: http://www.usnaviguide.com/ws-2008-02/presentation.pdf -John Coryat http://maps.huge.info http://www.usnaviguide.com --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "Google Maps API" group. To post to this group, send email to [email protected] To unsubscribe from this group, send email to [EMAIL PROTECTED] For more options, visit this group at http://groups.google.com/group/Google-Maps-API?hl=en -~----------~----~----~----~------~----~------~--~---
