code: function findNearCoords(err, postalObj) {
        if (err) throw err;
        if (!postalObj || postalObj === null) {
          throw new Error("No postal object found for zipcode "+zipcode+" using document attribute "
            +selectorAttr+"; make sure postal data has been loaded.");
        }
        var geoSearchParams = { 
          loc : { 
            $within: {
              $centerSphere : [postalObj.loc, milesToRadians(radiusMiles)], 
              $uniqueDocs:true
            }
          } 
        };
        dbCollection.find(geoSearchParams).limit(limit).toArray(this);
      }
docs: Take the lat/long coords and search for other zipcodes nearby: