How is $maxDistance measured in MongoDB?

Question

I can't seem to find this information. But using a geo search you can specify $maxDistance but for the life of me, I can't find if that is miles, kilometers, etc.

Here is a sample query I'm using:

db.hotels.find( { location: { $near : [18.74255, 99.03523], $maxDistance : 0.05 } } ).count()

Returns 15 (from my hotels database).

Thanks for any information.

John Flatness · Accepted Answer · 2011-03-16T01:42:15.100

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Unless you're doing a spherical query (like $nearSphere), MongoDB doesn't actually care about units, it just treats your locations as Cartesian coordinates.

So, the calculated distance is going to be in whatever your input units were. Since your $near point looks like standard lat/long, the $maxDistance in this case will be in units of degrees.

edited Mar 16 '11 at 01:42

answered Mar 16 '11 at 01:36

John Flatness

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What is units of degrees? I am doing the almost exact query as cbmeeks. What maxdistance should I set if I need results from within 1 km? – Jonathan Clark Oct 20 '11 at 14:40
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It's not exact, but for a rough conversion, you can divide your desired distance in kilometers by 111. (For miles, you would divide by about 69.) – John Flatness Oct 20 '11 at 17:35
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Just to be more exact since I just researched for this and this can clearly help future visitors, the actual formula is : 1° latitude = 69.047 miles = 111.12 kilometers – Dominic Goulet Jun 29 '12 at 16:29
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It is not so simple for longitude though, since the conversion factor changes with latitude. – Rasmus Storjohann Mar 04 '14 at 21:38

score 3 · Answer 2 · edited Nov 07 '16 at 13:02

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If you are using $near,

$maxDistance = your distance in Kms / 111

and if you use $nearSphere,

$maxDistance = your distance in kms/ 6378

where 6378 is the earths radius in kms

edited Nov 07 '16 at 13:02

Ingo Karkat

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answered Nov 07 '16 at 12:39

NIJESH ku

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How is $maxDistance measured in MongoDB?

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