#GeoJSON

RFC 7946.

def doc as geo.Document init geo.readGeojson($body);
def out as string init geo.writeGeojson($doc);

A position is [lon, lat] or [lon, lat, ele], longitude first as RFC 7946 fixes it, with elevation in metres above the WGS 84 ellipsoid. The deck swaps the order on read and write; there is nothing to configure.

#What is read

The document may be a FeatureCollection, a single Feature or a bare geometry.

Inner rings (holes) are dropped. Any other type, or a feature with no geometry, contributes nothing, so a collection that mixes a Point with something unsupported still yields the point. A position with fewer than two numbers, a coordinate out of range, or an array member of the wrong JSON type raises.

#Names live in properties

RFC 7946 does not define feature properties. The deck uses the common convention:

{
  "type": "Feature",
  "properties": {"name": "Nordkette", "description": "Alpine", "sym": "pin"},
  "geometry": {"type": "Point", "coordinates": [11.3889, 47.3122, 2334]}
}

name and description become the name and description; sym is this deck's own and round-trips through GeoJSON and GPX. A property that is missing or not a string reads as "".

#The document name is lost

A FeatureCollection has no title member, so $doc.name is not written:

def before as geo.Document init geo.open("hike.gpx");
def after as geo.Document init geo.readGeojson(geo.writeGeojson($before));

$after.name is empty whatever $before.name was. Per-feature names survive. The deck does not add a non-standard member, because other readers would ignore it.

#What is written

A FeatureCollection, indented, with one Feature per waypoint, route and track. A track with several segments becomes a MultiLineString, so the breaks survive; a segment of fewer than two points is left out, and a track with nothing left is not written. A route is not filtered: one of fewer than two points is written as a LineString RFC 7946 does not allow. Strings go through json.encode, so a name with a quote, a backslash or a newline round-trips exactly (testWriteGeojsonEscapesThroughTheJsonEncoder).