Mongo geoWithin error: Polygon coordinates must be an array - mongodb

Question

I have a data set with geo points.
{ _id ...other fields... location: { type: "Point", coordinates: [0,0]}}
What I have been attempting to do is filter out and delete any documents that have points that are in water bodies. I downloaded and converted a shape file of the earth's water bodies and stored that in a separate collection in the same database.
I have been trying to use Mongo's geoWithin function, but am not able to get it to work for me when I specify the water body's polygon document. If I hard code a polygon it works, but I don't really want to type in all the earth's water polygons into my code...
This doesn't work:
var geo = {type: "Point", coordinates: [0,0]}
db.waterBodies.find({
geo: {
$geoWithin: {
$geometry: {
type: 'Polygon',
coordinates: "$geometry.coordinates"
}
}
}
}).count()
or this
var geo = {type: "Point", coordinates: [0,0]}
var poly = [[[0,0],[0,3],[3,0],[0,0]]]
db.data.find({
geo: {
$geoWithin: {
$geometry: {
type: 'Polygon',
coordinates: "$poly"
}
}
}
}).count()
It generates this error:
E QUERY [js] uncaught exception: Error: count failed: { "ok" : 0, "errmsg" : "Polygon coordinates must be an array", "code" : 2,
"codeName" : "BadValue" } :
_getErrorWithCode#src/mongo/shell/utils.js:25:13 DBQuery.prototype.count#src/mongo/shell/query.js:376:11 #(shell):1:1
This works and doesn't throw an error but requires hard coded values:
var geo = {type: "Point", coordinates: [0,0]}
db.data.find({
geo: {
$geoWithin: {
$geometry: {
type: 'Polygon',
coordinates: [[[0,0],[0,3],[3,0],[0,0]]]
}
}
}
}).count()
and this
db.data.find({
'location.coordinates': {
$geoWithin: {
$geometry: {
type: 'Polygon',
coordinates: [[[0,0],[0,3],[3,0],[0,0]]]
}
}
}
}).count()
I of coarse don't want the count but used that for testing purposes.
The simple answer for me would look something like this:
const polygons = await getPolygons(); //get all the polygons from the water body's collection
const filter = {
'location.coordinates': { //the points I want to filter
$geoWithin: { //could also be geoIntersects
$geometry: {
type: 'MultiPolygon',
coordinates: polygons.geometry.coordinates //the water body polygons
}
}
}
};
try {
await db.collection(collection).deleteMany(filter);
} catch (e) {
if (e instanceof MongoError) {
Logger.info('Error deleting log');
throw e;
}
}
I would want to use multipolygon since there are many water bodies.
So far I have read everything I can find on google but nothing has worked for me. All the examples I have found hard code an array for the coordinates, but I don't want to do this.
Please help and let me know if there is a way to do this or to remove all points that are not found on land.
Thanks in advance.

Answer 1

Does this work for you?
db.data.insert({
geo: {
type: "Point",
coordinates: [0,0]
}
})
db.polygons.insert({
geo: {
type: "Polygon",
coordinates: [[[0,0],[0,3],[3,0],[0,0]]]
}
})
var polygon = db.polygons.findOne()
db.data.find({
geo: {
$geoWithin: {
$geometry: {
type: 'Polygon',
coordinates: polygon.geo.coordinates
}
}
}
}).count()