车辆监控项目，记录车辆GPS定位数据，我们在检测浙江省高速道路的时候，GPS热力图显示，结果变成这样了，如图：
MongoDB里，存储数据的格式是这样滴
{
"_id" : ObjectId("593e58b8d1eece32080d6632"),
"x" : 121.494230074275,
"y" : 29.6998736880818}
通过查询后，返回json格式是这样的：
{"lng":"121.98826732480999624","lat":"29.88628748150999925","count":1},{"lng":"122.00810540175000085","lat":"29.82699952501900142","count":1},{"lng":"122.00148151521000273","lat":"29.82556419141700133","count":1},{"lng":"122.09566082377000384","lat":"29.86581727309599898","count":1},{"lng":"121.99538599286999840","lat":"29.82299558164600128","count":1},{"lng":"121.98481996031999586","lat":"29.81670171825599880","count":1},{"lng":"121.97925141116000702","lat":"29.81335324424399857","count":1},{"lng":"121.96654822066000179","lat":"29.80203305154499915","count":1},{"lng":"121.96121962927000482","lat":"29.79876428024099866","count":1},{"lng":"121.94649301222000304","lat":"29.79243430893799882","count":1},{"lng":"121.94300499519999903","lat":"29.79132642105500040","count":1},{"lng":"121.93624256578000598","lat":"29.79261412193099900","count":1},{"lng":"121.92976345401000060","lat":"29.79086531288499984","count":1},{"lng":"121.91419359308000026","lat":"29.78270234553000151","count":1}
请问，有什么查询的方法，能够聚合一个点位的数据后，得到查询结果，就是后面的count值是聚合后的值，想到的类似mysql中的group by，但这又不是简单的group by，不知道有什么解决方案
个人理解是，一种思路是，在地图里面划分很多区域，对落在每个区域里面的位置（$geowithin）的个数进行统计。
供参考。
Love MongoDB! Have fun!
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