Converting long/lat to pixel x/y, given a zoom-level

Question

I\'m trying to develop a page in ASP.NET that will act as a tile-server for a Google Map

It will pull a collection of latitude/longitude points from the database, th

Answer 1

Here's some code I'm currently using. It's in PHP.

// Returns longitude in pixels at a certain zoom level
function lonToX($lon, $zoom) {
    $offset = 256 << ($zoom-1);
    return round($offset + ($offset * $lon / 180));
}
// Returns latitude in pixels at a certain zoom level
function latToY($lat, $zoom) {
    $offset = 256 << ($zoom-1);
    return round($offset - $offset/pi() * log((1 + sin($lat * pi() / 180)) / (1 - sin($lat * pi() / 180))) / 2);
}

Based on code from this page, written by this guy.

Good luck!

Update: This map is a great way to help understand how tiles work in Google Maps

Edit: Here's an equivalent set of functions in VB.NET:

Public Function LonToX(Lon As Double, Zoom as UInteger) As UInteger
    Dim Offset = 256 << (Zoom - 1)
    Return Math.Round(Offset + (Offset * Lon / 180))
End Function

Public Function LatToY(Lat As Double, Zoom as UInteger) As UInteger
    Dim Offset = 256 << (Zoom - 1)
    Return Math.Round(Offset - Offset / Math.Pi * Math.Log((1 + Math.Sin(Lat * Math.Pi / 180)) / (1 - Math.Sin(Lat * Math.Pi / 180))) / 2)
End Function

And in C#:

public uint lonToX(double lon, uint zoom) {
    uint offset = 256 << (zoom - 1);
    return Math.Round(offset + (offset * lon / 180));
}

public uint latToY(double lat, uint zoom) {
    uint offset = 256 << (zoom - 1);
    return Math.Round(offset - offset / Math.Pi * Math.Log((1 + Math.Sin(lat * Math.Pi / 180)) / (1 - Math.Sin(lat * Math.Pi / 180))) / 2);
}