constructors

This module contains functions that create new geographies from coordinates or already existing geographies.

ST_BEZIERSPLINE

ST_BEZIERSPLINE(geog, resolution, sharpness)

Description

Takes a line and returns a curved version of it by applying a Bezier spline algorithm. Note that the resulting geography will be a LineString with additional points inserted.

• geog: GEOGRAPHY input LineString.

• resolution: INT64|NULL total time in milliseconds assigned to the line. If NULL the default value 10000 is used. Internal curve vertices are generated in 10 ms increments, so the maximum number of resulting points will be resolution/10 (close points may be merged resulting in less points). A higher number will increase the accuracy of the result but will increase the computation time and number of points.

• sharpness: FLOAT64|NULL a measure of how curvy the path should be between splines. If NULL the default value 0.85 is used.

Example

carto-un

SELECT `carto-un`.carto.ST_BEZIERSPLINE(
  ST_GEOGFROMTEXT(
    "LINESTRING (-76.091308 18.427501,-76.695556 18.729501,-76.552734 19.40443,-74.61914 19.134789,-73.652343 20.07657,-73.157958 20.210656)"
  ),
  10000,
  0.9
);
-- LINESTRING(-76.091308 18.427501, -76.0916216712943 ...

carto-un-eu

manual

Additional examples

• Identifying earthquake-prone areas in the state of California

ST_MAKEELLIPSE

ST_MAKEELLIPSE(geog, xSemiAxis, ySemiAxis, angle, units, steps)

Description

Takes a Point and calculates the ellipse polygon given two semi-axes expressed in variable units and steps for precision.

• center: GEOGRAPHY center point.

• xSemiAxis: FLOAT64 semi (major) axis of the ellipse along the x-axis.

• ySemiAxis: FLOAT64 semi (minor) axis of the ellipse along the y-axis.

• angle: FLOAT64|NULL angle of rotation (along the horizontal axis), from East in decimal degrees, positive clockwise. If NULL the default value 0 is used.

• units: STRING|NULL units of length, the supported options are: miles, kilometers, and degrees. If NULLthe default value kilometers is used.

• steps: INT64|NULL number of steps. If NULL the default value 64 is used.

Example

carto-un

SELECT `carto-un`.carto.ST_MAKEELLIPSE(
  ST_GEOGPOINT(-73.9385,40.6643),
  5,
  3,
  -30,
  "miles",
  80
);
-- POLYGON((-73.8558575786687 40.7004828957859 ...

carto-un-eu

manual

ST_MAKEENVELOPE

ST_MAKEENVELOPE(xmin, ymin, xmax, ymax)

Description Creates a rectangular Polygon from the minimum and maximum values for X and Y.

• xmin: FLOAT64 minimum value for X.

• ymin: FLOAT64 minimum value for Y.

• xmax: FLOAT64 maximum value for X.

• ymax: FLOAT64 maximum value for Y.

Return type

GEOGRAPHY

Example

carto-un

SELECT `carto-un`.carto.ST_MAKEENVELOPE(0,0,1,1);
-- POLYGON((1 0, 1 1, 0 1, 0 0, 1 0))

carto-un-eu

manual

Additional examples

• Identifying earthquake-prone areas in the state of California

ST_TILEENVELOPE

ST_TILEENVELOPE(zoomLevel, xTile, yTile)

Description Returns the boundary polygon of a tile given its zoom level and its X and Y indices.

• zoomLevel: INT64 zoom level of the tile.

• xTile: INT64 X index of the tile.

• yTile: INT64 Y index of the tile.

Return type

GEOGRAPHY

Example

carto-un

SELECT `carto-un`.carto.ST_TILEENVELOPE(10,384,368);
-- POLYGON((-45 45.089035564831, -45 44.840290651398, -44.82421875 44.840290651398, -44.6484375 44.840290651398, -44.6484375 45.089035564831, -44.82421875 45.089035564831, -45 45.089035564831))

carto-un-eu

manual

Additional examples

• Census areas in the UK within tiles of multiple resolutions

This project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 960401.