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Version: 0.9

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).

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_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
    );

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]]