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Merge pull request #171 from CartoDB/great_circle_generator

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Adding function to produce a great circle between two points.
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Rafa de la Torre 2015-11-24 15:54:47 +01:00
commit bf711d5c9b
5 changed files with 47 additions and 0 deletions
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doc/CDB_GreatCircle.md Normal file
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Based on Paul Ramsey's [blog post](http://blog.cartodb.com/jets-and-datelines/).
#### Using the function
Creates a great circle line.
```sql
SELECT CDB_GreatCircle(start_point, end_point) FROM table_name
-- Results a line reprsenting the great circle between the two points
```
#### Arguments
CDB_GreatCircle(start_point, end_point)
* **start_point** ST_Point indicating the start of the line.
* **end_point** ST_point indicating the end of the line.

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-- Great circle point-to-point routes, based on:
-- http://blog.cartodb.com/jets-and-datelines/
--
CREATE OR REPLACE FUNCTION CDB_GreatCircle(start_point geometry, end_point geometry, max_segment_length NUMERIC DEFAULT 100000)
RETURNS geometry AS $$
DECLARE
line geometry;
BEGIN
line = ST_Segmentize(
ST_Makeline(
start_point,
end_point
)::geography,
max_segment_length
)::geometry;
IF ST_XMax(line) - ST_XMin(line) > 180 THEN
line = ST_Difference(
ST_Shift_Longitude(line),
ST_Buffer(ST_GeomFromText('LINESTRING(180 90, 180 -90)', 4326), 0.00001)
);
END IF;
RETURN line;
END;
$$
LANGUAGE 'plpgsql';

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scripts-enabled/241-CDB_GreatCircle.sql Symbolic link
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../scripts-available/CDB_GreatCircle.sql

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test/CDB_GreatCircle.sql Normal file
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select ST_AsText(CDB_GreatCircle(CDB_LatLng(55.8580,4.2590), CDB_LatLng(40.7127,74.0059)));
select ST_AsText(CDB_GreatCircle(CDB_LatLng(55.8580,4.2590), CDB_LatLng(40.7127,74.0059), 50000));

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LINESTRING(4.259 55.858,5.6692453115051 56.0150275120673,7.10720375678704 56.157400475677,8.5718366560563 56.2842986378254,10.0619272412891 56.3949153508462,11.5760785994189 56.4884642014437,13.1127142001617 56.564185934303,14.6700812655504 56.6213555706215,16.2462571744128 56.6592896061102,17.8391590143095 56.6773531596105,19.4465562981665 56.6749669334121,21.0660867567155 56.6516138405427,22.6952750058883 56.6068451534252,24.3315537765309 56.540286032869,25.9722872888145 56.4516403065472,27.6147962622065 56.3406943817481,29.2563839799455 56.207320197769,30.8943627796619 56.0514771479657,32.5260803224591 55.8732129290618,34.1489450028345 55.6726633044968,35.7604499005266 55.4500507979281,37.3581947399686 55.2056823610616,38.9399054089486 54.9399460854786,40.5034506895044 54.6533070499613,42.0468559644411 54.3463024122038,43.5683137754523 54.0195358662507,45.066191217402 53.673671594382,46.5390342525062 53.3094278446298,47.9855691138079 52.9275702630659,49.4047010366934 52.5289051040742,50.7955106088955 52.1142724327331,52.1572480633875 51.6845394219955,53.4893258557794 51.2405938343407,54.7913098701049 50.7833377637432,56.0629095865715 50.3136816997865,57.3039675245588 49.8325389621027,58.5144482465496 49.3408205404538,59.6944271762829 48.8394303639846,60.8440794494795 48.329261012675,61.9636689799149 47.811189874886,63.0535378889196 47.2860757471582,64.1140964137264 46.7547558660385,65.1458133802427 46.2180433565989,66.1492072992903 45.676725078361,67.1248381223566 45.131559846414,68.0732996734468 44.583277003498,68.9952127576034 44.0325753175597,69.8912189338183 43.4801221786776,70.7619749300985 42.9265530691612,71.6081476710291 42.3724712809595,72.4304098829428 41.8184478551838,73.2294362384225 41.2650217194684,74.0059 40.7127)
LINESTRING(4.259 55.858,4.96060044865294 55.9382939511593,5.6692453115051 56.0150275120673,6.38482117645567 56.0880973218335,7.10720375678705 56.157400475677,7.83625773770865 56.2228347173136,8.5718366560563 56.2842986378254,9.31378281572326 56.3416918804739,10.0619272412891 56.3949153508462,10.8160896721679 56.4438714316548,11.5760785994189 56.4884642014437,12.3416913471456 56.528599656387,13.1127142001617 56.5641859343031,13.8889225793161 56.5951335399513,14.6700812655504 56.6213555706215,15.4559446734179 56.6427679409819,16.2462571744128 56.6592896061102,17.0407534700619 56.6708427815999,17.8391590143095 56.6773531596105,18.6411904842936 56.6787501197174,19.4465562981665 56.6749669334121,20.2549571781681 56.6659409611101,21.0660867567155 56.6516138405428,21.8796322228404 56.6319316654367,22.6952750058883 56.6068451534252,23.5126914929996 56.5763098021872,24.3315537765309 56.5402860328691,25.1515304272452 56.4987393199198,25.9722872888145 56.4516403065472,26.7934882889404 56.3989649050969,27.6147962622065 56.3406943817482,28.4358737796488 56.2768154250305,29.2563839799456 56.207320197769,30.0759913971174 56.1322063721813,30.8943627796619 56.0514771479657,31.7111678961496 55.9651412533344,32.5260803224592 55.8732129290618,33.3387782060384 55.7757118957345,34.1489450028345 55.6726633044969,34.9562701828379 55.5640976716962,35.7604499005266 55.4500507979282,36.5611876268714 55.3305636720814,37.3581947399687 55.2056823610617,38.1511910717861 55.0754578859583,38.9399054089486 54.9399460854787,39.7240759459355 54.7992074675415,40.5034506895044 54.6533070499613,41.277787813601 54.5023141912026,42.0468559644411 54.3463024122039,42.8104345158644 54.1853492102971,43.5683137754524 54.0195358662508,44.3202951422663 53.8489472454711,45.066191217402 53.6736715943821,45.8058258688602 53.4938003329924,46.5390342525062 53.3094278446299,47.2656627911282 53.1206512637978,47.985569113808 52.9275702630661,48.6986219579803 52.7302868398744,49.4047010366934 52.5289051040743,50.1036968736777 52.3235310669909,50.7955106088955 52.1142724327332,51.4800537772815 51.9012383924278,52.1572480633875 51.6845394219956,52.8270250346284 51.4642870840378,53.4893258557795 51.2405938343408,54.1441009873167 51.0135728334539,54.791309870105 50.7833377637434,55.4309205988438 50.5500026522693,56.0629095865715 50.3136816997866,56.6872612224038 50.0744891161178,57.3039675245588 49.8325389621028,57.9130277905821 49.5879449982851,58.5144482465496 49.3408205404539,59.1082416968843 49.091278322122,59.6944271762829 48.8394303639847,60.2730296051101 48.5853878503721,60.8440794494795 48.3292610126751,61.40761238711 48.0711590197009,61.9636689799149 47.8111898748862,62.5122943541616 47.5494603202768,63.0535378889195 47.2860757471584,63.5874529134047 47.0211401132109,64.1140964137264 46.7547558660387,64.6335287494427 46.4870238729191,65.1458133802426 46.2180433565991,65.6510166029904 45.9479118369597,66.1492072992903 45.6767250783612,66.6404566936622 45.4045770424768,67.1248381223566 45.1315598464143,67.6024268127789 44.8577637259253,68.0732996734467 44.5832770034983,68.5375350943572 44.3081860611283,68.9952127576034 44.0325753175599,69.4464134580461 43.7565272097974,69.8912189338183 43.4801221786779,70.3297117064144 43.2034386583077,70.7619749300985 42.9265530691615,71.1880922503468 42.6495398146493,71.6081476710291 42.3724712809597,72.0222254300221 42.0954178399905,72.4304098829428 41.8184478551841,72.8327853946822 41.5416276900883,73.2294362384225 41.2650217194687,73.6204465018146 40.9886923428039,74.0059 40.7127)