PositionScheme class

A position scheme encapsulates position and bounding box factories for certain type of position data.

There are following known static constant instances available:

  • Position.scheme to create positions and boxes for any position data (geographic, projected or any other)
  • Projected.scheme to create projected positions and boxes
  • Geographic.scheme to create geographic positions and boxes

Examples (represented as test cases):

// a multi line string with two lines (when interpreted as geographic
// coordinates another west from and another east from the antimeridian)
final lines = [
  [177.0, -20.0, 178.0, -19.0, 179.0, -18.0].positions(Coords.xy),
  [-179.0, -17.0, -178.0, -16.0].positions(Coords.xy)
];
final mls = MultiLineString(lines);

// a minimum bounding box calculated from this geometry varies by scheme

// `Position.scheme`: a minimum bounding box is calculated mathematically
final b = Box.create(minX: -179.0, minY: -20.0, maxX: 179.0, maxY: -16.0);
expect(mls.calculateBounds(scheme: Position.scheme), b);
expect(mls.populated(scheme: Position.scheme).bounds, b);

// `Projected.scheme`: a minimum bounding box is calculated mathematically
const proj = ProjBox(minX: -179.0, minY: -20.0, maxX: 179.0, maxY: -16.0);
expect(mls.calculateBounds(scheme: Projected.scheme), proj);
expect(mls.populated(scheme: Projected.scheme).bounds, proj);

// `Geographic.scheme`: a minimum bounding box is calculated
// geographically and in this case it spans the antimeridian (that is
// `west > east` even if normally `west <= east` when not spanning)
const geo = GeoBox(west: 177.0, south: -20.0, east: -178.0, north: -16.0);
expect(mls.calculateBounds(scheme: Geographic.scheme), geo);
expect(mls.populated(scheme: Geographic.scheme).bounds, geo);
Annotations
  • @immutable

Constructors

PositionScheme({required CreatePosition<Position> position, required CreateBox<Box> box})
A position scheme with position and bounding box factories.
const

Properties

box → CreateBox<Box>
The factory to create bounding boxes.
no setter
hashCode → int
The hash code for this object.
no setterinherited
position → CreatePosition<Position>
The factory to create positions.
no setter
runtimeType → Type
A representation of the runtime type of the object.
no setterinherited

Methods

conformsWith(PositionScheme other) → bool
Returns true if this scheme conforms with other.
noSuchMethod(Invocation invocation) → dynamic
Invoked when a nonexistent method or property is accessed.
inherited
toString() → String
A string representation of this object.
inherited

Operators

operator ==(Object other) → bool
The equality operator.
inherited