h3_core library

H3 geospatial indexing for Dart/Flutter.

Uses dart:ffi on native, h3-js on web.

Classes

CellBoundary

Cell boundary as an ordered list of vertices in degrees.

CoordIJ

Local IJ coordinate pair for grid-local coordinate operations.

GeoPolygon

Polygon defined by an exterior ring and optional holes, for region operations such as polygonToCells.

H3Version

Version constants for the h3_core package and the underlying H3 C library.

LatLng

Latitude/longitude coordinate pair in degrees.

Enums

ContainmentMode

Containment mode for polygon fill operations.

Extension Types

H3Index

H3 cell, directed edge, or vertex index stored as a hex string.

Functions

areNeighborCells(H3Index origin, H3Index destination) → bool

Returns whether origin and destination share an edge.

cellAreaKm2(H3Index cell) → double

Returns the exact area of the cell in km².

cellAreaM2(H3Index cell) → double

Returns the exact area of the cell in m².

cellsToDirectedEdge(H3Index origin, H3Index destination) → H3Index

Returns the directed edge from origin to destination.

cellsToMultiPolygon(List<H3Index> cells) → List<List<List<LatLng>>>

Returns the outlines of a set of cells as a GeoJSON-style multi-polygon.

cellToBoundary(H3Index cell) → CellBoundary

Returns the boundary vertices of the given H3 cell.

cellToCenterChild(H3Index cell, int childRes) → H3Index

Returns the center child of cell at the finer childRes.

cellToChildPos(H3Index child, int parentRes) → int

Returns the position of child within its parent at parentRes.

cellToChildren(H3Index cell, int childRes) → List<H3Index>

Returns the children of cell at the finer childRes.

cellToLatLng(H3Index cell) → LatLng

Returns the center coordinate of the given H3 cell.

cellToLocalIj(H3Index origin, H3Index cell) → CoordIJ

Converts cell to local IJ coordinates relative to origin.

cellToParent(H3Index cell, int parentRes) → H3Index

Returns the parent cell of cell at the coarser parentRes.

cellToVertex(H3Index cell, int vertexNum) → H3Index

Returns the vertex at index vertexNum (0–5) of the cell.

cellToVertexes(H3Index cell) → List<H3Index>

Returns all vertices of the given cell.

childPosToCell(int childPos, H3Index parent, int childRes) → H3Index

Returns the child cell at childPos within parent at childRes.

compactCells(List<H3Index> cells) → List<H3Index>

Compacts a set of cells by replacing complete groups with their parent.

compactCellsAsync(List<H3Index> cells) → Future<List<H3Index>>

Async version of compactCells; runs on an isolate on native platforms.

constructCell(int res, int baseCellNumber, List<int> digits) → H3Index

Constructs an H3 cell index from res, baseCellNumber, and direction digits.

directedEdgeToBoundary(H3Index edge) → CellBoundary

Returns the boundary vertices of the directed edge.

directedEdgeToCells(H3Index edge) → List<H3Index>

Returns the origin and destination cells of the directed edge.

edgeLengthKm(H3Index edge) → double

Returns the exact length of the directed edge in kilometers.

edgeLengthM(H3Index edge) → double

Returns the exact length of the directed edge in meters.

getBaseCellNumber(H3Index h) → int

Returns the base cell number (0–121) of the given H3 index.

getDirectedEdgeDestination(H3Index edge) → H3Index

Returns the destination cell of the directed edge.

getDirectedEdgeOrigin(H3Index edge) → H3Index

Returns the origin cell of the directed edge.

getHexagonAreaAvgKm2(int resolution) → double

Returns the average hexagon area in km² at the given resolution.

getHexagonAreaAvgM2(int resolution) → double

Returns the average hexagon area in m² at the given resolution.

getHexagonEdgeLengthAvgKm(int resolution) → double

Returns the average hexagon edge length in km at the given resolution.

getHexagonEdgeLengthAvgM(int resolution) → double

Returns the average hexagon edge length in meters at the given resolution.

getIcosahedronFaces(H3Index h) → List<int>

Returns the icosahedron face(s) that the given cell intersects.

getIndexDigit(H3Index h, int resolution) → int

Returns the direction digit at the given resolution for index h.

getNumCells(int resolution) → int

Returns the total number of cells at the given resolution.

getPentagons(int resolution) → List<H3Index>

Returns all 12 pentagon cells at the given resolution.

getRes0Cells() → List<H3Index>

Returns all 122 resolution-0 cells.

getResolution(H3Index h) → int

Returns the resolution (0–15) of the given H3 index.

greatCircleDistanceKm(LatLng a, LatLng b) → double

Returns the great-circle distance between a and b in kilometers.

greatCircleDistanceM(LatLng a, LatLng b) → double

Returns the great-circle distance between a and b in meters.

gridDisk(H3Index origin, int k) → List<H3Index>

Returns all cells within k grid steps of origin (filled disk).

gridDiskAsync(H3Index origin, int k) → Future<List<H3Index>>

Async version of gridDisk; runs on an isolate on native platforms.

gridDiskDistances(H3Index origin, int k) → Map<H3Index, int>

Returns cells within k steps of origin mapped to their grid distance.

gridDistance(H3Index origin, H3Index destination) → int

Returns the minimum grid distance between origin and destination.

gridPathCells(H3Index start, H3Index end) → List<H3Index>

Returns the cells along the shortest grid path from start to end.

gridRing(H3Index origin, int k) → List<H3Index>

Returns cells exactly k grid steps from origin (hollow ring).

h3ToString(H3Index h) → String

Returns the hex string representation of the given H3 index.

isPentagon(H3Index h) → bool

Returns whether h is a pentagon cell.

isResClassIII(H3Index h) → bool

Returns whether h has Class III resolution orientation.

isValidCell(H3Index h) → bool

Returns whether h is a valid H3 cell index.

isValidDirectedEdge(H3Index edge) → bool

Returns whether edge is a valid H3 directed edge index.

isValidIndex(H3Index h) → bool

Returns whether h is any valid H3 index (cell, edge, or vertex).

isValidVertex(H3Index vertex) → bool

Returns whether vertex is a valid H3 vertex index.

latLngToCell(LatLng latLng, int resolution) → H3Index

Converts a latLng coordinate to the H3 cell index at the given resolution (0–15).

localIjToCell(H3Index origin, CoordIJ ij) → H3Index

Converts local ij coordinates relative to origin back to an H3 cell.

originToDirectedEdges(H3Index origin) → List<H3Index>

Returns all directed edges originating from origin.

pentagonCount() → int

Returns the number of pentagons per resolution (always 12).

polygonToCells(GeoPolygon polygon, int resolution) → List<H3Index>

Returns all cells whose centers are within the polygon at resolution.

polygonToCellsAsync(GeoPolygon polygon, int resolution) → Future<List<H3Index>>

Async version of polygonToCells; runs on an isolate on native platforms.

polygonToCellsExperimental(GeoPolygon polygon, int resolution, {ContainmentMode mode = ContainmentMode.center}) → List<H3Index>

Returns cells within the polygon using the specified containment mode.

res0CellCount() → int

Returns the number of resolution-0 cells (always 122).

reverseDirectedEdge(H3Index edge) → H3Index

Returns the directed edge with origin and destination swapped.

stringToH3(String hex) → H3Index

Parses a hex string into an H3Index, throwing H3Exception on invalid input.

uncompactCells(List<H3Index> cells, int resolution) → List<H3Index>

Expands compacted cells to the given resolution.

uncompactCellsAsync(List<H3Index> cells, int resolution) → Future<List<H3Index>>

Async version of uncompactCells; runs on an isolate on native platforms.

vertexToLatLng(H3Index vertex) → LatLng

Returns the coordinates of the given vertex.

Exceptions / Errors

H3Exception

Exception thrown when an H3 operation fails.