Wrong distance calculation with MongoDB

Question

I am executing the following raw query with MongoDB:

qry = {\"position\" : SON([(\"$near\", [52.497309,13.39385]), (\"$maxDistance\", distance/111.12 )])}
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Answer 1

MongoDB assumes that coordinates are in (long, lat) format. If you compute distances by hand using Great-circle distance you'll see what is going on:

> from math import acos, sin, cos, radians
>
> long_x, lat_x = [radians(y) for y in [52.473266, 13.45494]]
> long_y, lat_y = [radians(y) for y in [52.497309, 13.39385]]
>
> acos(sin(lat_x) * sin(lat_y) + cos(lat_x) * cos(lat_y) * cos(long_x - long_y)) * 6371.0
7.27362435031

Google takes coordinates in (lat, long) format so if you provide the same input Google interpretation will be like below:

> acos(sin(long_x) * sin(long_y) + cos(long_x) * cos(long_y) * cos(lat_x - lat_y)) * 6371.0
4.92535867182