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 (optional): INT total time in milliseconds assigned to the line. By default resolution is 10000. 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 (optional): DOUBLE a measure of how curvy the path should be between splines. By default sharpness is 0.85.

Return type

GEOGRAPHY

Examples

SELECT CARTO.CARTO.ST_BEZIERSPLINE(
  TO_GEOGRAPHY(
    '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)'
  )
);
-- { "coordinates": [ [ -76.091308, 18.427501 ], [ -76.09134585033101, 18.427508082543092 ], ...

SELECT CARTO.CARTO.ST_BEZIERSPLINE(
  TO_GEOGRAPHY(
    '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
);
-- { "coordinates": [ [ -76.091308, 18.427501 ], [ -76.09134585033101, 18.427508082543092 ], ...

SELECT CARTO.CARTO.ST_BEZIERSPLINE(
  TO_GEOGRAPHY(
    '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
);
-- { "coordinates": [ [ -76.091308, 18.427501 ], [ -76.09134541990707, 18.42750717125151 ], ...

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: DOUBLE semi (major) axis of the ellipse along the x-axis.

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

• angle (optional): DOUBLE angle of rotation (along the horizontal axis), from East in decimal degrees, positive clockwise. By default angle is 0.

• units (optional): STRING units of length, the supported options are: miles, kilometers, and degrees. By default units is kilometers.

• steps (optional): INT number of steps. By default steps is 64.

Return type

GEOGRAPHY

Examples

SELECT CARTO.CARTO.ST_MAKEELLIPSE(ST_Point(-73.9385,40.6643), 5, 3);
-- { "coordinates": [ [ [ -73.87922034627275, 40.6643 ], [ -73.88056149301754, 40.67000644486112 ], ...

SELECT CARTO.CARTO.ST_MAKEELLIPSE(ST_Point(-73.9385,40.6643), 5, 3, -30);
-- { "coordinates": [ [ [ -73.88715365786175, 40.68678300909311 ], [ -73.89207802212195, 40.691215338152176 ], ...

SELECT CARTO.CARTO.ST_MAKEELLIPSE(ST_Point(-73.9385,40.6643), 5, 3, -30, 'miles');
-- { "coordinates": [ [ [ -73.85585757866869, 40.700482895785946 ], [ -73.8637839804274, 40.70761511598624 ], ...

SELECT CARTO.CARTO.ST_MAKEELLIPSE(ST_Point(-73.9385,40.6643), 5, 3, -30, 'miles', 80);
-- { "coordinates": [ [ [ -73.85585757866869, 40.700482895785946 ], [ -73.86194538052666, 40.70635901954343 ], ...

Additional examples

• Enrichment of catchment areas for store characterization

ST_MAKEENVELOPE

ST_MAKEENVELOPE(xmin, ymin, xmax, ymax)

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

• xmin: DOUBLE minimum value for X.

• ymin: DOUBLE minimum value for Y.

• xmax: DOUBLE maximum value for X.

• ymax: DOUBLE maximum value for Y.

Return type

GEOGRAPHY

Example

SELECT CARTO.CARTO.ST_MAKEENVELOPE(0,0,1,1);
-- { "coordinates": [ [ [ 0, 0 ], [ 0, 1 ], [ 1, 1 ], [ 1, 0 ], [ 0, 0 ] ] ], "type": "Polygon" }

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: INT zoom level of the tile.

• xTile: INT X index of the tile.

• yTile: INT Y index of the tile.

Return type

GEOGRAPHY

Example

SELECT CARTO.CARTO.ST_TILEENVELOPE(10,384,368);
-- {"coordinates": [[[-45,45.08903556483103], [-45, 44.840290651397986], ...