Functions / Geometry Functions (return a geometry) |

Returns a MultiPolygon geometry object which represents a buffered distance around another geometry object.

MI_Buffer ( geometry, dist, unit, calculationType, res )

`geometry` is an expression which returns a geometry,

`dist` is a number which represents the distance from the source geometry for the buffer,

`unit` is an area unit specification,

`calculationType` is a string that indicates whether to perform a Spherical or Cartesian calculation. There is no default, and

`res` is a number which specifies the minimum number of segments used in creating a circle from buffering a point.

The geometry object returned is in the same coordinate system as the supplied `geometry` argument. The distance (`dist`) is in the units specified by the `units` argument. If `res` is NULL or zero, a reasonable default value is used. Otherwise, `res` must be at least 3. The minimum number of segments used in fractional circles, such as formed when buffering the corners of a rectangle, will be proportionally smaller. (for example, a half circle will have at least res/2 segments). The distance may be either positive or negative.

Valid values for `unit` are the following distance units:

Value | Description |
---|---|

mi | miles |

km | kilometers |

in | inches |

ft | feet |

yd | yards |

mm | millimeters |

cm | centimeters |

m | meters |

survey ft | US Survey feet |

nmi | nautical miles |

twip | twips |

pt | points |

pica | picas |

degree | degrees |

li | links |

ch | chains |

rd | rods |