About 2D indexes
A %2d% *geo* index wants two elements. With the first being the
longitude (*x*) and the second one being the latitude (*y*) (as in
GeoJSON).
The following are all equivalent:
$myCol->insert( [
_id: 42, loc: [ 6.43, 52.1233 ]
] );
$myCol->insert( [
_id: 42, loc: { long: 6.43, lat: 52.1233 }
] );
$myCol->insert( [
_id: 42, loc: { latitude: 6.43, longitude: 52.1233 }
] );