Google App Engine Geohashing

Question

I am writing a web application using GWT and App Engine. My application will need to post and query items based on their latitude, longitude.

As a result of google\

Answer 1

Instead of defining a bounding box with 4 coordinates (min and max latitude, min and max longitude), you can define it with the coordinates of the North-West corner of the box, and two parameters : resolution and slice. The resolution defines the scale of the box, it is implemented as the number of figures below the decimal-point. The slice is the width and height of the box, using the least significant figure as its unit.

The comments in geobox.py explain this in more details, with good examples :

To query for members of a bounding box, we start with some input coordinates like lat=37.78452 long=-122.39532 (both resolution 5). We then round these coordinates up and down to the nearest "slice" to generate a geobox. A "slice" is how finely to divide each level of resolution in the geobox. The minimum slice size is 1, the maximum does not have a limit, since larger slices will just spill over into lower resolutions (hopefully the examples will explain).

Some examples:

resolution=5, slice=2, and lat=37.78452 long=-122.39532: "37.78452|-122.39532|37.78450|-122.39530"

resolution=5, slice=10, and lat=37.78452 long=-122.39532: "37.78460|-122.39540|37.78450|-122.39530"

resolution=5, slice=25, and lat=37.78452 long=-122.39532: "37.78475|-122.39550|37.78450|-122.39525"