Lookup geointersect

Working with Data
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1

So I know I can write the following MongoDB function which is able to tell me if a set point is inside another geospatial area. However I can’t seem to use the let function to be able to use the data from the first $match as that has it’s own geospatial data that I want to use for the query.

Query Match Sample


{
 "_id":ObjectId('5f58816115890cf60f3a4d5e')
  "location": {
    "coordinates": [
      115.8621,
      -31.9674
    ],
    "type": "Point"
  }
}

The Query

[{
 $match: {
  _id: ObjectId('5f58816115890cf60f3a4d5e')
 }
}, {
 $lookup: {
  from: 'CPM',
  'let': {
   sD: '$_id'
  },
  pipeline: [
   {
    $match: {
     geometry: {
      $geoIntersects: {
       $geometry: {
        type: 'Point',
        coordinates: [
         115.8621,
         -31.9674
        ]
       }
      }
     }
    }
   }
  ],
  as: 'CPM'
 }
}]

And it works fine, however how do I take the location information from “A” Collection to use in the $lookup pipeline?

I tried:

{
  from: "CPM",
  let:{'location:'$location'},
  pipeline:[{$match:{
  geometry: {
    $geoIntersects: {
      $geometry: {'$$location'}
    }
  },
}}],
as:'CPM'
}

Thinking it would get the location section of the query from A collection but it did not.