Block clockwise WKT polygons from searches and downloads

[MattBlissett]

We currently have different behaviour regarding WKT polygons between ElasticSearch (search and small downloads) and Hive (large downloads).

The WKT specification requires a normal polygon to be counterclockwise. A clockwise polygon represents a hole, i.e. the whole world except that polygon.

A few tools generate clockwise polygons. We've had problems with this before. It is presumably a rare requirement to have the whole world except some polygon, and if that is required it can be specified by

• providing multiple, smaller polygons
• providing a whole-world polygon with a hole
• lat/long greater/lessthan comparisons

I suggest we reject queries where the outer polygon is clockwise as 400 Bad Request, ideally with a suitable error message explaining the problem. (Could even give the reversed polygon...)

Some earlier issues:

• problem with pred_within() - results outside polygon in the download ropensci/rgbif#704
• Empty download file supposedly containing 800.000+ records portal-feedback#2222
• ERROR: Your filters might be invalid or the servers having issues. //when searching for occurrences using (latitude, longitude) portal-feedback#4131
• Downloads being killed portal-feedback#2032
• Bounding box queries failing when submitted to API via R portal-feedback#1769
• dubious records of Onobrychis arenaria portal-feedback#1251
• Two similar but different geometries giving exact same results #38

[MattBlissett]

See also https://codepen.io/GBIFS/pen/mdgdrrJ

[jhnwllr]

I get this error message now from rgbif when trying to do clockwise downloads. Is this expected now?

Error: Polygon with clockwise exterior ring: POLYGON ((8.64152 66.10075, 20.24262 63.18351, 24.24534 58.63805, 19.49635 52.6679, 10.74464 53.54985, 5.11369 60.53765, 8.64152 66.10075)). Did you mean these coordinates? (Note this is only part of the polygon or multipolygon you provided.) LINEARRING (8.64152 66.10075, 5.11369 60.53765, 10.74464 53.54985, 19.49635 52.6679, 24.24534 58.63805, 20.24262 63.18351, 8.64152 66.10075)

[MortenHofft]

Yes. A clockwise wkt polygon is a hole and not supported. Unless inside a enclosing polygon (counter clockwise winding)

[MattBlissett]

Clockwise rectangles are still accepted.