Are there OpenStreetMap/MapQuest-hosted map tile attributes I am unaware of?

Question

I am in the process of changing how I get my map images from Google maps api to the MapQuest-hosted map tiles which uses OpenStreetMap Data. I am switching from Google maps because I hit the daily request limit which I wasn't expecting and I am not using OpenStreet api because although their data is free, their tiles have a limit and all I need is an image. Therefore, here I am using the MapQuest-hosted map tiles.

I think I understand it, but there are some things that I would like to be able to do but cannot find any documentation on it. For example, I would like to have an image size of 500x300 if possible, or at least 512*512 (double 256*256 which is what the tiles come out to be). I would also like to be able to display a marker. Is this possible?

I used this code found here to convert my latitude and longitude data into x and y coordinates:

 public class slippy {
 public static void main(String[] args) {
 int zoom = 9;
 double lat = 42.8549;
 double lon = -78.863;
 System.out.println("http://otile1.mqcdn.com/tiles/1.0.0/map/" + getTileNumber(lat, lon, zoom) + ".png");
 }
 public static String getTileNumber(final double lat, final double lon, final int zoom)    {
 int xtile = (int)Math.floor( (lon + 180) / 360 * (1<<zoom) ) ;
 int ytile = (int)Math.floor( (1 - Math.log(Math.tan(Math.toRadians(lat)) + 1 / Math.cos(Math.toRadians(lat))) / Math.PI) / 2 * (1<<zoom) ) ;
return("" + zoom + "/" + xtile + "/" + ytile);
}
}

I used this code to generate two links to a map of Buffalo; one with a zoom of 9, here, and one with 10 ,here, and the center seems to differ. Is this a result of using open source data or is there an attribute I could use?

Answer 1

Of course the center differs. From one zoom level to the next, one tile is "split" into four other tiles. Consequently the center of the single tile will be located at the corners of the four tiles. Using the mentioned formula you will always get the tile which contains your coordinates. But due to the nature of tiles it won't be necessarily at the center of the tile. For each specific coordinate there is only one tile at a given zoom level containing it. Hence the coordinate can be anywhere on the tile and not necessarily at the center.

Still I'm not quite sure what you actually want to achieve. For displaying tiles (and markers) all you need to do is using Leaflet or OpenLayers (or any another library supporting the tiles concept).

And keep in mind that MapQuest also has terms of use.

Edit:

An alternative would be to use a WMS service instead of a TMS which does the resizing and concatenation of the tiles for you. With a WMS you just have to define a bounding box around your center and an image size. The resulting image will always be centered around the coordinates. The OSM wiki has a list of OSM WMS servers.

Don't forget to get informed about the usage policy of the WMS service you choose.