MultiPolygon, a standard type

Several areas, at least one, that belong together.

Use it for one region made of separate pieces, such as a country with islands. For one connected area, use Polygon.

Shape

Field	Type	Required?
`polygons`	`List<Polygon>`	Yes

Its parts keep these rules, and a value that breaks one fails with the rule's name:

altitudes_agree: every position with an altitude, or none

Example

example

MultiPolygon {    polygons: [        Polygon {            outer: [                Point { latitude: 0.0 longitude: 0.0 altitude: none },                Point { latitude: 0.0 longitude: 1.0 altitude: none },                Point { latitude: 1.0 longitude: 1.0 altitude: none },                Point { latitude: 0.0 longitude: 0.0 altitude: none }            ]            holes: []        }    ]}

Good to know

== tells you whether two are the same. < and list.sort_by don't take it, so sort by one of its parts instead.

In JSON

A GeoJSON geometry, with each position's longitude first, in a request, a response or json.write:

json

{"type":"MultiPolygon","coordinates":[[[[0,0],[1,0],[1,1],[0,1],[0,0]]],[[[2,2],[3,2],[3,3],[2,3],[2,2]]]]}{"type":"MultiPolygon","coordinates":[[[[0,0],[1,0],[1,1],[0,1],[0,0]]]]}

Details

Text form, storage, how it is shown, and operations

MultiPolygon is in the group Geospatial, and has been in Jadpo since 0.1.0.

Text form

It has no single text form, so text.from and text.parse don't take it.

How it is stored

It is stored in one column named for the field, of type geography. {"type":"MultiPolygon","coordinates":[[[[0,0],[1,0],[1,1],[0,1],[0,0]]]]} is stored as 'SRID=4326;MULTIPOLYGON (((0 0, 1 0, 1 1, 0 1, 0 0)))'::geography.

How it is shown to people

text.format(value, locale:) shows it to people in their locale.

With locale: Locale.en_gb:

Value	Shown
`{"type":"MultiPolygon","coordinates":[[[[0,0],[1,0],[1,1],[0,1],[0,0]]],[[[2,2],[3,2],[3,3],[2,3],[2,2]]]]}`	`(((0°, 0°; 0°, 1° E; 1° N, 1° E; 1° N, 0°; 0°, 0°)), ((2° N, 2° E; 2° N, 3° E; 3° N, 3° E; 3° N, 2° E; 2° N, 2° E)))`
`{"type":"MultiPolygon","coordinates":[[[[0,0],[1,0],[1,1],[0,1],[0,0]]]]}`	`(((0°, 0°; 0°, 1° E; 1° N, 1° E; 1° N, 0°; 0°, 0°)))`

Operations

geo.area(shape: T) -> Area: A Polygon's or MultiPolygon's area on the ellipsoid, each edge a geodesic and each ring the smaller of the two sides it bounds, holes taken away, rounded half to even to the square millimetre.
geo.bounding_box(shape: T) -> BoundingBox: The smallest box of parallels and meridians holding the shape, an edge's highest or lowest point counted, across the antimeridian when that box is narrower; a shape holding a pole runs from -180 to 180.
geo.centroid(shape: T) -> Point: The shape's centre on the sphere, as PostGIS's ST_Centroid(x, false) finds it: each point a unit vector, weighted by area, length or count by the shape's kind, summed, and back to latitude and longitude. It may lie outside a concave polygon.
geo.contains(a: T, b: U) -> Bool: Whether no point of b lies outside a, edges included. a may be a BoundingBox, whose sides are compared directly, or a Circle, holding the points within its radius of its centre.
geo.intersects(a: T, b: U) -> Bool: Whether the two share at least one point, edges included.
geo.to_wkt(shape: T) -> Text: The shape as WKT, longitude first, as PostGIS's ST_AsText writes it: POINT(-0.1276 51.5072), POINT Z (-0.1276 51.5072 35) with an altitude, each ring in the order it holds its points.
geo.within(a: T, b: U, distance: Length?) -> Bool: geo.contains(b, a); or, with distance:, whether two points are at most that far apart, as geo.distance measures them.

It also takes text.format, json.read, json.write and ==. How every standard type behaves says how they work.