mgold / elm-geojson Goto Github PK

Differences between the original spec and the RFC include:

• Remove CRS (#1)
• Feature object id may be either a string or a number. (While inconvenient, I'm glad they resolved the ambiguity present in the original spec.)
• Antimeridian Cutting. Haven't had a chance to read the RFC to see the impact of this.
• Positions are no longer supposed to have more than three coordinates.

Hi, is it possible to support 0.19 now that it's been released?

Hi, looks good but I haven't actually used it yet.

One issue, in my mailing list post I linked to an older version of the spec, and while working on it I noticed that it was deprecated in favor of the official one: https://tools.ietf.org/html/rfc7946

In the official spec, CRS has been removed, and all GeoJSON objects are expected to use the WGS84 CRS: https://tools.ietf.org/html/rfc7946#section-4

So I think the maybe CRS and associated tests need to be removed.

I'd fork and pull-request, but my Elm skills are really weak at this point...

We currently define positions as

type alias Position = ( Float, Float, List Float )

I would like to define them as

type alias Position = ( Float, Float, Float )

RFC 7946 section B.1. (second bullet) states

In the absence of elevation values, applications sensitive to height or depth SHOULD interpret positions as being at local ground or sea level (see Section 4).

which states

An OPTIONAL third-position element SHALL be the height in meters above or below the WGS 84 reference ellipsoid. In the absence of elevation values, applications sensitive to height or depth SHOULD interpret positions as being at local ground or sea level.

Therefore, decoding would use 0 as the third position if it was not present in the JSON. Encoding would remove any zeroes, since

Furthermore B.1. states

Implementations SHOULD NOT extend position arrays beyond 3 elements

which we currently do.

Although all of these are SHOULD recommendations not MUST requirements, it's good to follow them. The downside is that it requires a major version bump, and anyone using out-of-compliance geoJSON will be broken.