geohashing

问题 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's distributed database design you can't simple query a set of inequalities. Instead they suggest doing geohashing. The method is described on this page. http://code.google.com/appengine/articles/geosearch.html Essentially you pre compute a bounding box so that you can query items that have been tagged with that bounding box. There

问题 if length of geohash string is more, it is more accurate. But is there any direct relationship like if length is 7 it is providing 100 meter accuracy, i.e. if two geohash (and either of their bounding box) is having first 7 char matching, both should be near 100 meter etc? I am using geohash for finding, all near-by location for given geohash, with their distance Also any directway to calculate distance between two geo-hash? (one way is to decode them to lat/lng, and then calculate distance)