Write a GeoJSON-LD howto

[sgillies]

Things to cover:

• What is GeoJSON-LD? It's just normal GeoJSON with @context added to define the standard GeoJSON terms.
• What is the base GeoJSON-LD context? It's the one containing definitions only of the required and recommended GeoJSON terms ("type", "geometry", etc).
• How to use the base context in GeoJSON documents.
• How to use the base context with documents that don't provide a context.
• The differences between GeoJSON "type" and JSON-LD "@type" and how to use them.
• The differences between GeoJSON "id" and JSON-LD "@id" and how to use them.
• How to override the base context within GeoJSON-LD.

[sthagen]

I like this list and it helps me a lot in trying to follow this endeavor, but could you be so kind as to expand a bit on the relation of the second and the last list item? What does e.g.. overriding the base context mean, when the base context is the union set of required and recommended terms. Does this mean values are changed, where the keys are in the aforementioned set? … are we trying to give rules, what is allowed to override and what not? Thanks a lot in advance and sorry, if my question is unreadable. All the best, Stefan.

[sgillies]

Overriding example: a user might want "type" within a properties object to have a different sense from "http://geojson.org/vocab#type" and will have to add a local context to the properties object. See the second context in

http://json-ld.org/playground/#startTab=tab-expanded&json-ld=%7B%22%40context%22%3A%7B%22type%22%3A%22http%3A%2F%2Fgeojson.org%2Fvocab%23type%22%2C%22properties%22%3A%22http%3A%2F%2Fgeojson.org%2Fvocab%23properties%22%7D%2C%22type%22%3A%22Feature%22%2C%22properties%22%3A%7B%22%40context%22%3A%7B%22type%22%3A%22http%3A%2F%2Fexample.com%2Fothervocab%23type%22%7D%2C%22type%22%3A%22Foo%22%7D%7D&context=%7B%7D

and notice what happens when you remove it. The JSON-LD is pretty cool!

[sgillies]

Next action: expand the README with a "how to" section.

[sgillies]

See #42.