问题描述
我正在努力使我了解MongoDB和地理空间搜索.基本上我想要的是用户能够查询的文档(图像)是在距用户当前位置一定距离内拍摄的.因此，我要搜索用户在距他站立的位置1公里以内拍摄的所有图像下面的示例，但我不知道将什么设置为最大距离值.
I am trying to get my head around MongoDB and geospatial searches.Basically what I want is for users to be able to query documents (images) thatare shot within a set distance from the users current location. So I the user is searching for all images that are shot within 1 km from where he is standing I try to use the below example but I have no idea what to set as the maxdistance value.
db.places.find({ loc : { $near : [50,50] , $maxDistance : 5 }})
所以我的问题是，如果我要搜索文档，应将maxdistance设置为什么?半径1公里之内?
So my question is what do I set as maxdistance if I am searching for documentswithin a 1 km radius?
我完全被困在这里.
推荐答案
为了在km范围内使用mongodb $near查询，您需要将半径值转换为km.默认情况下，mongodb $ near接受$maxDistance作为radius.
In order to use mongodb $near queries with km bounds, you need to convert the radius value to km. By default mongodb $near accepts $maxDistance as radius.
使用km时，将距离转换为111.12(一个度约为111.12公里)，或者保持距离不变.
Convert distance by 111.12 (one degree is approximately 111.12 kilometers) when using km, or leave distance as it is on using degree
对您的问题
您可以使用此
db.places.find( { loc : { $near : [50,50] , $maxDistance : 1/111.12 } } )
我已经回答了如何在此处使用 mongo地理空间特征详细信息.您可以签出
I have answered how to use mongo geospatial features here in detail. You can check out
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