Is it valid to have a properties element in an geoJSON featureCollection?

Question

Is it valid to have a properties element with a featureCollection-element as parent?

This is, according to geojson.org valid:

{ "type": "FeatureCollection",
  "features": [
              { "type": "Feature",
                "geometry": {"type": "Point", "coordinates": [102.0, 0.5]},
                "properties": {"prop0": "value0"}
              }
              ]
}

But I can't find is it is valid nor if it is in-valid to have this:

{ "type": "FeatureCollection",
  "properties" : { "description" : "This is the geometry for..." }
  "features": [
              { "type": "Feature",
                "geometry": {"type": "Point", "coordinates": [102.0, 0.5]},
                "properties": {"prop0": "value0"}
              }
              ]
}

According to the answer underneath it is not in-valid to put it there, but programs/scripts won't know its there.

So, let me rephrase the question: (Where) Is it possible to put some descriptive information about the property as a total??

Answer 1

The short answer is no - it is not valid to have a properties element on a FeatureCollection object:

https://www.rfc-editor.org/rfc/rfc7946#section-7.1

The GeoJSON "geometry" and "properties" members define a Feature object. FeatureCollection and Geometry objects, respectively, MUST NOT contain a "geometry" or "properties" member.

Answer 2

2.3. Feature Collection Objects

A GeoJSON object with the type "FeatureCollection" is a feature collection object.

An object of type "FeatureCollection" must have a member with the name "features". The value corresponding to "features" is an array. Each element in the array is a feature object as defined above.

I think this clearly implies that if the object has additional members that doesn't make it invalid.

Ecmascript objects are very open.

So yes, you can have a properties element at the top level of a feature collection, but don't expect any tools to know its there, or to copy it, ...

Answer 3

I too think that a top level 'properties' would be useful, one at the feature collection level.

But the work around that I did was to make an additional feature for the feature collection, populate the properties as desired, and just set the geometry object to NULL. From my reading of the spec, this seems allowed and stays within the standard.

Answer 4

I don't have enough reputation yet to comment, so I will post in the form of an answer in support of https://gis.stackexchange.com/a/25309/217561

There are at least three sections of the spec that are relevant. As https://gis.stackexchange.com/users/7207/julian points out, the description of FeatureCollection doesn't mention "properties".

I think https://gis.stackexchange.com/a/209263/217561 is overlooking "respectively" in the spec which to me indicates that a FeatureCollection cannot have a "geometry" and a Geometry cannot have a "properties".

Further as https://gis.stackexchange.com/users/9181/natevw's comment indicates the spec states that other members not defined in the spec are valid but may not be interpreted by clients and could reduce interoperability.

To me this all adds up to the conclusion that adding a "properties" member to a FeatureCollection is a valid way to add collection level information and is aligned with the conventions of geojson.

Answer 5

You can insert a Polygon feature without any coordinates and set your properties as you like:

{
  "type": "FeatureCollection",
  "features": [
    {
      "type": "Feature",
      "geometry": {
        "type": "Polygon",
        "coordinates": [          
        ]
      },
      "properties": {
        "description": "This is the geometry for..."
      }
    },
    {
      // Other features
    }
  ]
}