Grid traversal functions

Grid traversal allows finding cells in the vicinity of an origin cell, and determining how to traverse the grid from one cell to another.

gridDisk

C

H3Error gridDisk(H3Index origin, int k, H3Index* out);

Python

h3.grid_disk(origin, k)

Java

List<Long> gridDisk(long origin, int k);
List<String> gridDisk(String origin, int k);

JavaScript (Live)

h3.gridDisk(origin, k)

Live Editor

function example() { const h = '85283473fffffff'; const k = 5; return h3.gridDisk(h, k); }

function example() {
  const h = '85283473fffffff';
  const k = 5;
  return h3.gridDisk(h, k);
}

Result

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gridDisk produces indices within k distance of the origin index.

gridDisk was previously named k-ring after the concept of a ring with distance k. k-ring 0 is defined as the origin index, k-ring 1 is defined as k-ring 0 and all neighboring indices, and so on.

Output is placed in the provided array in no particular order. Elements of the output array may be left as zero, which can happen when crossing a pentagon.

maxGridDiskSize

C

H3Error maxGridDiskSize(int k, int64_t *out);

Python

note

This function exists for memory management and is not exposed.

Java

note

This function exists for memory management and is not exposed.

JavaScript (Live)

note

This function exists for memory management and is not exposed.

Maximum number of indices that result from the gridDisk algorithm with the given k.

gridDiskDistances

C

H3Error gridDiskDistances(H3Index origin, int k, H3Index* out, int* distances);

Python

h3.grid_disk_distances(origin, k)

Java

List<List<Long>> gridDiskDistances(long origin, int k);
List<List<String>> gridDiskDistances(String origin, int k);

JavaScript (Live)

h3.gridDiskDistances(origin, k)

Live Editor

function example() { const h = '85283473fffffff'; const k = 5; return h3.gridDiskDistances(h, k); }

function example() {
  const h = '85283473fffffff';
  const k = 5;
  return h3.gridDiskDistances(h, k);
}

Result

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gridDiskDistances produces indices within k distance of the origin index.

k-ring 0 is defined as the origin index, k-ring 1 is defined as k-ring 0 and all neighboring indices, and so on.

Output is placed in the provided array in no particular order. Elements of the output array may be left as zero, which can happen when crossing a pentagon.

gridDiskUnsafe

C

H3Error gridDiskUnsafe(H3Index origin, int k, H3Index* out);

Python

h3.grid_disk_unsafe(h, k)

Java

List<List<Long>> gridDiskUnsafe(Long h3, int k) throws PentagonEncounteredException;
List<List<String>> gridDiskUnsafe(String h3Address, int k) throws PentagonEncounteredException;

JavaScript (Live)

note

This function is not exposed.

gridDiskUnsafe produces indexes within k distance of the origin index. The function returns an error code when one of the returned by this function is a pentagon or is in the pentagon distortion area. In this case, the output behavior of the out array is undefined.

k-ring 0 is defined as the origin index, k-ring 1 is defined as k-ring 0 and all neighboring indexes, and so on.

Output is placed in the provided array in order of increasing distance from the origin. The provided array must be of size maxGridDiskSize(k).

Returns 0 (E_SUCCESS) if no pentagonal distortion is encountered.

gridDiskDistancesUnsafe

C

H3Error gridDiskDistancesUnsafe(H3Index origin, int k, H3Index* out, int* distances);

Python

h3.grid_disk_distances_unsafe(h, k)

Java

note

This function is not exposed because the same functionality is exposed by gridDiskUnsafe

JavaScript (Live)

note

This function is not exposed.

gridDiskDistancesUnsafe produces indexes within k distance of the origin index. Output behavior is undefined when one of the indexes returned by this function is a pentagon or is in the pentagon distortion area.

k-ring 0 is defined as the origin index, k-ring 1 is defined as k-ring 0 and all neighboring indexes, and so on.

Output is placed in the provided array in order of increasing distance from the origin. The distances in hexagons is placed in the distances array at the same offset. The provided array must be of size maxGridDiskSize(k).

Returns 0 (E_SUCCESS) if no pentagonal distortion is encountered.

gridDiskDistancesSafe

C

H3Error gridDiskDistancesSafe(H3Index origin, int k, H3Index* out, int* distances);

Python

h3.grid_disk_distances_safe(h, k)

Java

note

This function is not exposed because the same functionality is exposed by gridDiskSafe

JavaScript (Live)

note

This function is not exposed.

gridDiskDistancesSafe produces indexes within k distance of the origin index.

k-ring 0 is defined as the origin index, k-ring 1 is defined as k-ring 0 and all neighboring indexes, and so on.

Output is placed in the provided array in order of increasing distance from the origin. The distances in hexagons is placed in the distances array at the same offset. The provided array must be of size maxGridDiskSize(k).

Returns 0 (E_SUCCESS) on success.

gridDisksUnsafe

C

H3Error gridDisksUnsafe(H3Index* h3Set, int length, int k, H3Index* out);

Python

h3.grid_disks_unsafe(h, k)

Java

note

This function is not exposed because the same functionality is exposed by gridDiskUnsafe

JavaScript (Live)

note

This function is not exposed.

gridDisksUnsafe takes an array of input hex IDs and a max k and returns an array of hexagon IDs sorted first by the original hex IDs and then by the grid k-ring (0 to max), with no guaranteed sorting within each grid k-ring group.

Returns 0 (E_SUCCESS) if no pentagonal distortion was encountered. Otherwise, output is undefined

gridRingUnsafe

C

H3Error gridRingUnsafe(H3Index origin, int k, H3Index* out);

Python

h3.grid_ring_unsafe(h, k)

Java

List<Long> gridRingUnsafe(long h3, int k) throws PentagonEncounteredException;
List<String> gridRingUnsafe(String h3Address, int k) throws PentagonEncounteredException;

JavaScript (Live)

h3.gridRingUnsafe(h3Index, k)

Live Editor

function example() { const h = '85283473fffffff'; const k = 1; return h3.gridRingUnsafe(h, k); }

function example() {
  const h = '85283473fffffff';
  const k = 1;
  return h3.gridRingUnsafe(h, k);
}

Result

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Produces the hollow hexagonal ring centered at origin with sides of length k.

Returns 0 (E_SUCCESS) if no pentagonal distortion was encountered.

gridPathCells

C

H3Error gridPathCells(H3Index start, H3Index end, H3Index* out);

Python

h3.grid_path_cells(start, end)

Java

List<Long> gridPathCells(long start, long end) throws LineUndefinedException
List<String> gridPathCells(String startAddress, String endAddress) throws LineUndefinedException

JavaScript (Live)

h3.gridPathCells(start, end)

Live Editor

function example() { const start = '85283473fffffff'; const end = '8528342bfffffff'; return h3.gridPathCells(start, end); }

function example() {
  const start = '85283473fffffff';
  const end = '8528342bfffffff';
  return h3.gridPathCells(start, end);
}

Result

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Given two H3 indexes, return the line of indexes between them (inclusive).

This function may fail to find the line between two indexes, for example if they are very far apart. It may also fail when finding distances for indexes on opposite sides of a pentagon.

Notes:

• The specific output of this function should not be considered stable across library versions. The only guarantees the library provides are that the line length will be h3Distance(start, end) + 1 and that every index in the line will be a neighbor of the preceding index.

• Lines are drawn in grid space, and may not correspond exactly to either Cartesian lines or great arcs.

gridPathCellsSize

C

H3Error gridPathCellsSize(H3Index start, H3Index end, int64_t* size);

Python

note

This function exists for memory management and is not exposed.

Java

note

This function exists for memory management and is not exposed.

JavaScript (Live)

note

This function exists for memory management and is not exposed.

Number of indexes in a line from the start index to the end index, to be used for allocating memory.

Returns 0 (E_SUCCESS) on success, or an error if the line cannot be computed.

gridDistance

C

H3Error gridDistance(H3Index origin, H3Index h3, int64_t *distance);

Python

h3.grid_distance(h1, h2)

Java

long gridDistance(long a, long b) throws DistanceUndefinedException;
long gridDistance(String a, String b) throws DistanceUndefinedException;

JavaScript (Live)

h3.gridDistance(a, b)

Live Editor

function example() { const start = '85283473fffffff'; const end = '8528342bfffffff'; return h3.gridDistance(start, end); }

function example() {
  const start = '85283473fffffff';
  const end = '8528342bfffffff';
  return h3.gridDistance(start, end);
}

Result

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Provides the distance in grid cells between the two indexes.

Returns 0 (E_SUCCESS) on success, or an error if finding the distance failed. Finding the distance can fail because the two indexes are not comparable (different resolutions), too far apart, or are separated by pentagonal distortion. This is the same set of limitations as the local IJ coordinate space functions.

cellToLocalIj

C

H3Error cellToLocalIj(H3Index origin, H3Index h3, uint32_t mode, CoordIJ *out);

Python

h3.cell_to_local_ij(origin, h)

Java

CoordIJ cellToLocalIj(long origin, long h3) throws PentagonEncounteredException, LocalIjUndefinedException;
CoordIJ cellToLocalIj(String originAddress, String h3Address) throws PentagonEncounteredException, LocalIjUndefinedException;

JavaScript (Live)

h3.cellToLocalIj(origin, h3)

Live Editor

function example() { const origin = '85283473fffffff'; const h = '8528342bfffffff'; const {i, j} = h3.cellToLocalIj(origin, h); return [i, j]; }

function example() {
  const origin = '85283473fffffff';
  const h = '8528342bfffffff';
  const {i, j} = h3.cellToLocalIj(origin, h);
  return [i, j];
}

Result

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Produces local IJ coordinates for an H3 index anchored by an origin.

mode is reserved for future expansion and must be set to 0.

This function's output is not guaranteed to be compatible across different versions of H3.

localIjToCell

C

H3Error localIjToCell(H3Index origin, const CoordIJ *ij, uint32_t mode, H3Index *out);

Python

h3.local_ij_to_cell(origin, i, j)

Java

long localIjToCell(long origin, CoordIJ ij) throws LocalIjUndefinedException;
String localIjToCell(String originAddress, CoordIJ ij) throws LocalIjUndefinedException;

JavaScript (Live)

h3.localIjToCell(origin, coords)

Live Editor

function example() { const h = '85283473fffffff'; const coords = {i: 0, j: 0}; return h3.localIjToCell(h, coords); }

function example() {
  const h = '85283473fffffff';
  const coords = {i: 0, j: 0};
  return h3.localIjToCell(h, coords);
}

Result

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Produces an H3 index from local IJ coordinates anchored by an origin.

mode is reserved for future expansion and must be set to 0.

This function's output is not guaranteed to be compatible across different versions of H3.