Working with the spherical 2D geospatial model

The spherical 2D MongoDB geospatial model is used for situations where coordinates need to be located on a sphere. An obvious example would be creating queries that provide locations on planet Earth, the moon, or other planetary bodies. Here is the command that creates a GeoJSON object from existing coordinates in the properties collection. Again, please note the use of $toDouble to convert latitude and longitude values from string to double:

db.properties.aggregate(
    { "$match": {} },
    {
        "$addFields": {
            "address.geo_spatial":{
                "type":"Point",
                "coordinates":
                [
                    { "$toDouble" : "$address.longitude" },
                    { "$toDouble" : "$address.latitude" }
                ]
            }
        }
    },
 { "$out" : "properties" }
);

This...