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Alexey Milovidov 2019-12-09 03:02:50 +03:00
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dbms/src/Functions/greatCircleDistance.cpp
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@ -14,17 +14,22 @@
namespace DB
{
/** https://en.wikipedia.org/wiki/Great-circle_distance
*
* The function calculates distance in meters between two points on Earth specified by longitude and latitude in degrees.
* The function uses great circle distance formula https://en.wikipedia.org/wiki/Great-circle_distance .
* Throws exception when one or several input values are not within reasonable bounds.
* Latitude must be in [-90, 90], longitude must be [-180, 180].
* Original code of this implementation of this function is here https://github.com/sphinxsearch/sphinx/blob/409f2c2b5b2ff70b04e38f92b6b1a890326bad65/src/sphinxexpr.cpp#L3825.
* Andrey Aksenov, the author of original code, permitted to use this code in ClickHouse under the Apache 2.0 license.
* Presentation about this code from Highload++ Siberia 2019 is here https://github.com/ClickHouse/ClickHouse/files/3324740/1_._._GEODIST_._.pdf
* The main idea of this implementation is optimisations based on Taylor series, trigonometric identity and calculated constants once for cosine, arcsine(sqrt) and look up table.
*/
/** Calculates the distance between two geographical locations.
* There are two variants:
* greatCircleDistance: calculates the distance on a sphere: https://en.wikipedia.org/wiki/Great-circle_distance
* geoDistance: calculates the distance on WGS-84 ellipsoid.
*
* The function calculates distance in meters between two points on Earth specified by longitude and latitude in degrees.
*
* Latitude must be in [-90, 90], longitude must be [-180, 180].
*
* Original code of this implementation of this function is here:
* https://github.com/sphinxsearch/sphinx/blob/409f2c2b5b2ff70b04e38f92b6b1a890326bad65/src/sphinxexpr.cpp#L3825.
* Andrey Aksenov, the author of original code, permitted to use this code in ClickHouse under the Apache 2.0 license.
* Presentation about this code from Highload++ Siberia 2019 is here https://github.com/ClickHouse/ClickHouse/files/3324740/1_._._GEODIST_._.pdf
* The main idea of this implementation is optimisations based on Taylor series, trigonometric identity
* and calculated constants once for cosine, arcsine(sqrt) and look up table.
*/
namespace
{