Geo spatial functions

GEODIST()

GEODIST(lat1, lon1, lat2, lon2, [...]) function calculates the geosphere distance between two points specified by their coordinates. Note that by default, both latitudes and longitudes must be in radians, and the result will be in meters. You can use arbitrary expressions for any of the four coordinates. An optimized path will be chosen when one pair of arguments directly refers to a pair of attributes, and the other one is constant.

GEODIST() also accepts an optional 5th argument, allowing you to easily convert between input and output units and select the specific geodistance formula to use. The complete syntax and a few examples are as follows:

GEODIST(lat1, lon1, lat2, lon2, { option=value, ... })

GEODIST(40.7643929, -73.9997683, 40.7642578, -73.9994565, {in=degrees, out=feet})

GEODIST(51.50, -0.12, 29.98, 31.13, {in=deg, out=mi})

The known options and their values are:

  • in = {deg | degrees | rad | radians}, specifies the input units;
  • out = {m | meters | km | kilometers | ft | feet | mi | miles}, specifies the output units;
  • method = {adaptive | haversine}, specifies the geodistance calculation method.

The default method is "adaptive". It is a well-optimized implementation that is both more precise and much faster at all times than "haversine".

GEOPOLY2D()

GEOPOLY2D(lat1,lon1,lat2,lon2,lat3,lon3...) creates a polygon to be used with the CONTAINS() function. This function takes into account the Earth's curvature by tessellating the polygon into smaller ones, and should be used for larger areas. For small areas, the POLY2D() function can be used instead. The function expects coordinates to be pairs of latitude/longitude coordinates in degrees; if radians are used, it will give the same result as POLY2D().

POLY2D()

POLY2D(x1,y1,x2,y2,x3,y3...) creates a polygon to be used with the CONTAINS() function. This polygon assumes a flat Earth, so it should not be too large; for large areas, the GEOPOLY2D() function, which takes Earth's curvature into consideration, should be used.