linestring centroids

[missinglink]

this PR introduces a second centroid function for line strings, this is useful for things like roads and rail routes. see pelias/openstreetmap#72

it's easier to review the commits one-by-one

note: the method OSM uses to define polygons is a massive hack and so any way which does not have the same co-ordinate value for its first and last node will be considered a line, eg:

this is technically correct as ways must be closed to be considered polygons, the above image shows the two different centroid algorithms used for http://www.openstreetmap.org/way/28596356

this makes a big difference for rail networks because the centroid now actually lies on the line string:

for all polygons (closed ways) the original sphere centroid calc is still used, I deleted it from this code base as it's now been merged in to the go.geo library.

// determine if the way is a closed centroid or a linestring
// by comparing first and last coordinates.
isClosed := false
if points.Length() > 2 {
  isClosed = points.First().Equals(points.Last())
}

// compute the centroid using one of two different algorithms
var compute *geo.Point
if isClosed {
  compute = GetPolygonCentroid(points)
} else {
  compute = GetLineCentroid(points)
}

resolves: pelias/openstreetmap#72

[orangejulius]

Nice, LGTM

[dianashk]

LGTM (small caveat: I don't really know Go)

[missinglink]

$ npm publish
+ [email protected]

[riordan]

looks go to me

god this is exciting!

[dianashk]

👋 hi @riordan!

[riordan]

I miss y'all!

On Aug 10 2016, at 5:54 pm, Diana Shkolnikov [email protected] wrote:

👋 hi @riordan!

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