Version: nightly

Geospatial Functions

This page lists all geospatial related functions in GreptimeDB. These functions are enabled when you have common-function/geo feature turned on (default: on).

Geo Types

Convert data between geospatial types.

`wkt_point_from_latlng`

Convert latitude and longitude to WKT point.

SELECT wkt_point_from_latlng(37.76938, -122.3889) AS point;

Geohash

See more about geohash encoding algorithms.

`geohash`

Get geohash encoded string from latitude, longitude and resolution.

SELECT geohash(37.76938, -122.3889, 11);

`geohash_neighbours`

Get all geohash neighbours for given coordinate and resolution.

Note that this function returns a String array and it only works on our HTTP Query API and Postgres channel.

SELECT geohash_neighbours(37.76938, -122.3889, 11);

H3

H3 is a geospatial index algorithm. See more about h3 encoding.

`h3_latlng_to_cell`

Encode coordinate (latitude, longitude) into h3 index at given resolution. Returns UInt64 representation of the cell.

SELECT h3_latlng_to_cell(37.76938, -122.3889, 1);

`h3_latlng_to_cell_string`

Similar to h3_latlng_to_cell but returns hex encoding of the cell.

h3_latlng_to_cell_string(37.76938, -122.3889, 1);

`h3_cell_to_string`

Convert cell index (UInt64) to its string representation.

SELECT h3_cell_to_string(h3_latlng_to_cell(37.76938, -122.3889, 8));

`h3_string_to_cell`

Convert hex-encoded cell ID to its UInt64 form

h3_string_to_cell(h3_latlng_to_cell_string(37.76938, -122.3889, 8::UInt64));

`h3_cell_center_latlng`

Returns cell centroid as latitude and longitude.

Note that this function returns a Float array and it only works on our HTTP Query API and Postgres channel.

SELECT h3_cell_center_latlng(h3_latlng_to_cell(37.76938, -122.3889, 8));

`h3_cell_resolution`

Returns resolution for given cell.

SELECT h3_cell_resolution(h3_latlng_to_cell(37.76938, -122.3889, 8));

`h3_cell_base`

Returns the base cell of given cell.

SELECT h3_cell_base(h3_latlng_to_cell(37.76938, -122.3889, 8));

`h3_cell_is_pentagon`

Returns true if cell is a pentagon.

SELECT h3_cell_is_pentagon(h3_latlng_to_cell(37.76938, -122.3889, 8));

`h3_cell_parent`

Returns parent cell at given resolution.

h3_cell_parent(h3_latlng_to_cell(37.76938, -122.3889, 8), 6);

`h3_cell_to_children`

Returns children cells at given resolution.

Note that this function returns a UInt64 array and it only works on our HTTP Query API and Postgres channel.

h3_cell_to_children(h3_latlng_to_cell(37.76938, -122.3889, 8), 10);

`h3_cell_to_children_size`

Returns cell children count at given resolution.

h3_cell_to_children_size(h3_latlng_to_cell(37.76938, -122.3889, 8), 10);

`h3_cell_to_child_pos`

Return the child position for its parent at given resolution. Position is the index of child in its children.

h3_cell_to_child_pos(h3_latlng_to_cell(37.76938, -122.3889, 8), 6)

`h3_child_pos_to_cell`

Returns the cell at given position of the parent at given resolution.

Arguments:

position
cell index
resolution

h3_child_pos_to_cell(25, h3_latlng_to_cell(37.76938, -122.3889, 8), 11);

`h3_cells_contains`

Return true if given cells contains cell, or cell's parent.

Arguments:

cell set: it can be int64/uint64/string array, and comma-separated string cell ID.
cell index: the cell to test

SELECT
    h3_cells_contains('86283470fffffff,862834777ffffff, 862834757ffffff, 86283471fffffff, 862834707ffffff', '8b283470d112fff') AS R00,
    h3_cells_contains(['86283470fffffff', '862834777ffffff', '862834757ffffff', '86283471fffffff', '862834707ffffff'], '8b283470d112fff') AS R11,
    h3_cells_contains([604189641255419903, 604189643000250367, 604189642463379455, 604189641523855359, 604189641121202175], 604189641792290815) AS R21;

`h3_grid_disk`

Returns cells with k distances of given cell.

Note that this function returns a UInt64 array and it only works on our HTTP Query API and Postgres channel.

h3_grid_disk(h3_latlng_to_cell(37.76938, -122.3889, 8), 3);

`h3_grid_disk_distances`

Returns all cells within k distances of given cell.

Note that this function returns a UInt64 array and it only works on our HTTP Query API and Postgres channel.

h3_grid_disk_distance(h3_latlng_to_cell(37.76938, -122.3889, 8), 3);

`h3_grid_distance`

Returns distance between two cells.

SELECT
    h3_grid_distance(cell1, cell2) AS distance,
FROM
    (
      SELECT
          h3_latlng_to_cell(37.76938, -122.3889, 8) AS cell1,
          h3_latlng_to_cell(39.634, -104.999, 8) AS cell2
    );

`h3_grid_path_cells`

Returns path cells between two cells. Note that this function can fail if two cells are very far apart.

SELECT
    h3_grid_path_cells(cell1, cell2) AS path_cells,
FROM
    (
      SELECT
          h3_latlng_to_cell(37.76938, -122.3889, 8) AS cell1,
          h3_latlng_to_cell(39.634, -104.999, 8) AS cell2
    );

`h3_distance_sphere_km`

Returns sphere distance between centroid of two cells, in km

SELECT
    round(h3_distance_sphere_km(cell1, cell2), 5) AS sphere_distance
FROM
    (
      SELECT
          h3_string_to_cell('86283082fffffff') AS cell1,
          h3_string_to_cell('86283470fffffff') AS cell2
    );

`h3_distance_degree`

Returns euclidean distance between centroid of two cells, in degree.

SELECT
    round(h3_distance_degree(cell1, cell2), 14) AS euclidean_distance
FROM
    (
      SELECT
          h3_string_to_cell('86283082fffffff') AS cell1,
          h3_string_to_cell('86283470fffffff') AS cell2
    );

S2

Learn more about S2 encoding.

`s2_latlng_to_cell`

Returns s2 cell index of given coordinate.

SELECT s2_latlng_to_cell(37.76938, -122.3889);

`s2_cell_to_token`

Returns string representation of given cell.

SELECT s2_cell_to_token(s2_latlng_to_cell(37.76938, -122.3889));

`s2_cell_level`

Returns s2 level of given cell.

SELECT s2_cell_level(s2_latlng_to_cell(37.76938, -122.3889));

`s2_cell_parent`

Returns parent of given cell at level.

SELECT s2_cell_parent(s2_latlng_to_cell(37.76938, -122.3889), 3);

Encodings

`json_encode_path`

Encode rows of latitude, longitude in a JSON array, sorted by timestamp.

Arguments:

latitude
longitude
timestamp

Returns a JSON array in string type. Note that the sequence in result coordinate is [longitude, latitude] to align with GeoJSON spec.

SELECT json_encode_path(lat, lon, ts);

Example output:

[[-122.3888,37.77001],[-122.3839,37.76928],[-122.3889,37.76938],[-122.382,37.7693]]