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Version: 0.10

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]]

Spatial Relation​

st_contains​

Test spatial relationship between two objects: contains.

Arguments: two spatial objects encoded with WKT.

SELECT
    st_contains(polygon1, p1),
    st_contains(polygon2, p1),
FROM
    (
        SELECT
            wkt_point_from_latlng(37.383287, -122.01325) AS p1,
            'POLYGON ((-122.031661 37.428252, -122.139829 37.387072, -122.135365 37.361971, -122.057759 37.332222, -121.987707 37.328946, -121.943754 37.333041, -121.919373 37.349145, -121.945814 37.376705, -121.975689 37.417345, -121.998696 37.409164, -122.031661 37.428252))' AS polygon1,
            'POLYGON ((-121.491698 38.653343, -121.582353 38.556757, -121.469721 38.449287, -121.315883 38.541721, -121.491698 38.653343))' AS polygon2,
    );

st_within​

Test spatial relationship between two objects: within.

Arguments: two spatial objects encoded with WKT.

SELECT
    st_within(p1, polygon1),
    st_within(p1, polygon2),
 ROM
    (
        SELECT
            wkt_point_from_latlng(37.383287, -122.01325) AS p1,
            'POLYGON ((-122.031661 37.428252, -122.139829 37.387072, -122.135365 37.361971, -122.057759 37.332222, -121.987707 37.328946, -121.943754 37.333041, -121.919373 37.349145, -121.945814 37.376705, -121.975689 37.417345, -121.998696 37.409164, -122.031661 37.428252))' AS polygon1,
            'POLYGON ((-121.491698 38.653343, -121.582353 38.556757, -121.469721 38.449287, -121.315883 38.541721, -121.491698 38.653343))' AS polygon2,
    );

st_intersects​

Test spatial relationship between two objects: intersects.

Arguments: two spatial objects encoded with WKT.

SELECT
    st_intersects(polygon1, polygon2),
    st_intersects(polygon1, polygon3),
FROM
    (
        SELECT
            'POLYGON ((-122.031661 37.428252, -122.139829 37.387072, -122.135365 37.361971, -122.057759 37.332222, -121.987707 37.328946, -121.943754 37.333041, -121.919373 37.349145, -121.945814 37.376705, -121.975689 37.417345, -121.998696 37.409164, -122.031661 37.428252))' AS polygon1,
            'POLYGON ((-121.491698 38.653343, -121.582353 38.556757, -121.469721 38.449287, -121.315883 38.541721, -121.491698 38.653343))' AS polygon2,
            'POLYGON ((-122.089628 37.450332, -122.20535 37.378342, -122.093062 37.36088, -122.044301 37.372886, -122.089628 37.450332))' AS polygon3,
    );

Spatial Measurement​

st_distance​

Returns WGS84(SRID: 4326) euclidean distance between two geometry object, in degree.

Arguments: two spatial objects encoded with WKT.

SELECT
    st_distance(p1, p2) AS euclidean_dist,
    st_distance(p1, polygon1) AS euclidean_dist_pp,
FROM
    (
        SELECT
            wkt_point_from_latlng(37.76938, -122.3889) AS p1,
            wkt_point_from_latlng(38.5216, -121.4247) AS p2,
            'POLYGON ((-121.491698 38.653343, -121.582353 38.556757, -121.469721 38.449287, -121.315883 38.541721, -121.491698 38.653343))' AS polygon1,
    );

st_distance_sphere_m​

Return great circle distance between two point, in meters.

Arguments: two spatial objects encoded with WKT.

SELECT
    st_distance_sphere_m(p1, p2) AS sphere_dist_m,
FROM
    (
        SELECT
            wkt_point_from_latlng(37.76938, -122.3889) AS p1,
            wkt_point_from_latlng(38.5216, -121.4247) AS p2,
    );

st_area​

Returns area of given geometry object.

Arguments: the spatial object encoded with WKT.

SELECT
    st_area(p1) as area_point,
    st_area(polygon1) as area_polygon,
FROM
    (
        SELECT
            wkt_point_from_latlng(37.76938, -122.3889) AS p1,
            'POLYGON ((-121.491698 38.653343, -121.582353 38.556757, -121.469721 38.449287, -121.315883 38.541721, -121.491698 38.653343))' AS polygon1,
    );