diff --git a/geojson/poly/LICENSE b/geojson/poly/LICENSE
new file mode 100644
index 00000000..f820c7bd
--- /dev/null
+++ b/geojson/poly/LICENSE
@@ -0,0 +1,21 @@
+Copyright (c) 2016 Josh Baker
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in
+all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+THE SOFTWARE.
+Contact GitHub API Training Shop Blog About
+
diff --git a/geojson/poly/README.md b/geojson/poly/README.md
new file mode 100644
index 00000000..4a7b11e7
--- /dev/null
+++ b/geojson/poly/README.md
@@ -0,0 +1,14 @@
+Poly
+====
+[![Build Status](https://travis-ci.org/tidwall/poly.svg?branch=master)](https://travis-ci.org/tidwall/poly)
+[![GoDoc](https://godoc.org/github.com/tidwall/poly?status.svg)](https://godoc.org/github.com/tidwall/poly)
+
+Polygon detection methods for Go. 
+
+Contact
+-------
+Josh Baker [@tidwall](http://twitter.com/tidwall)
+
+License
+-------
+Poly source code is available under the MIT [License](/LICENSE).
diff --git a/geojson/poly/inside.go b/geojson/poly/inside.go
index 271a81ef..3ba6ae33 100644
--- a/geojson/poly/inside.go
+++ b/geojson/poly/inside.go
@@ -42,10 +42,10 @@ func insideshpext(p Point, shape Polygon, exterior bool) bool {
 	in := false
 	for i := 0; i < len(shape); i++ {
 		res := raycast(p, shape[i], shape[(i+1)%len(shape)])
-		if res == on {
+		if res.on {
 			return exterior
 		}
-		if res == left {
+		if res.in {
 			in = !in
 		}
 	}
diff --git a/geojson/poly/inside_test.go b/geojson/poly/inside_test.go
index 6f961e91..a79296f8 100644
--- a/geojson/poly/inside_test.go
+++ b/geojson/poly/inside_test.go
@@ -34,6 +34,14 @@ func TestRayInside(t *testing.T) {
 	testRayInside(t, P(1, -0.1), strange, false)
 }
 
+func TestRayInside2(t *testing.T) {
+	normal := []Point{P(0, 0), P(4, 3), P(5, 2), P(0, 0)}
+	testRayInside(t, P(1, 2), normal, false)
+	testRayInside(t, P(1, 3), normal, false)
+	testRayInside(t, P(4, 2), normal, true)
+	testRayInside(t, P(2, 1), normal, true)
+}
+
 var texterior = Polygon{
 	P(0, 0),
 	P(0, 6),
@@ -74,6 +82,10 @@ func TestRayExteriorHoles(t *testing.T) {
 		{P(8, -3), false},
 		{P(8, 1), false},
 		{P(14, -1), false},
+
+		{P(8, -0.5), true},
+		{P(8, -1.5), true},
+		{P(8, -1), true},
 	}
 	// add the edges, all should be inside
 	for i := 0; i < len(texterior); i++ {
diff --git a/geojson/poly/intersects.go b/geojson/poly/intersects.go
index 64fd9a7a..96a5f71b 100644
--- a/geojson/poly/intersects.go
+++ b/geojson/poly/intersects.go
@@ -9,6 +9,8 @@ func (p Point) Intersects(exterior Polygon, holes []Polygon) bool {
 func (shape Polygon) Intersects(exterior Polygon, holes []Polygon) bool {
 	return shape.doesIntersects(false, exterior, holes)
 }
+
+// LineStringIntersects detects if a polygon intersects a linestring
 func (shape Polygon) LineStringIntersects(exterior Polygon, holes []Polygon) bool {
 	return shape.doesIntersects(true, exterior, holes)
 }
diff --git a/geojson/poly/poly.go b/geojson/poly/poly.go
index 377d5691..4ce00ced 100644
--- a/geojson/poly/poly.go
+++ b/geojson/poly/poly.go
@@ -1,8 +1,9 @@
+// Package poly provides polygon detection methods.
 package poly
 
 import "fmt"
 
-// Point is simple 3D point
+// Point is simple 2D point
 type Point struct {
 	X, Y, Z float64
 }
diff --git a/geojson/poly/raycast.go b/geojson/poly/raycast.go
index 1648561f..e841127e 100644
--- a/geojson/poly/raycast.go
+++ b/geojson/poly/raycast.go
@@ -1,121 +1,95 @@
 package poly
 
-// This implementation of the raycast algorithm test if a point is
-// to the left of a line, or on the segment line. Otherwise it is
-// assumed that the point is outside of the segment line.
+import "math"
 
-type rayres int
-
-func (r rayres) String() string {
-	switch r {
-	default:
-		return "unknown"
-	case out:
-		return "out"
-	case left:
-		return "left"
-	case on:
-		return "on"
-	}
+type rayres struct {
+	in, on bool
 }
 
-const (
-	out  = rayres(0) // outside of the segment.
-	left = rayres(1) // to the left of the segment
-	on   = rayres(2) // on segment or vertex, special condition
-)
-
 func raycast(p, a, b Point) rayres {
+	// make sure that the point is inside the segment bounds
+	if a.Y < b.Y && (p.Y < a.Y || p.Y > b.Y) {
+		return rayres{false, false}
+	} else if a.Y > b.Y && (p.Y < b.Y || p.Y > a.Y) {
+		return rayres{false, false}
+	}
+
+	// test if point is in on the segment
 	if a.Y == b.Y {
-		// A and B share the same Y plane.
 		if a.X == b.X {
-			// AB is just a point.
-			if p.X == a.X && p.Y == a.Y {
-				return on
+			if p == a {
+				return rayres{false, true}
+			} else {
+				return rayres{false, false}
 			}
-			return out
 		}
-		// AB is a horizontal line.
-		if p.Y != a.Y {
-			// P is not on same Y plane as A and B.
-			return out
-		}
-		// P is on same Y plane as A and B
-		if a.X < b.X {
-			if p.X >= a.X && p.X <= b.X {
-				return on
+		if p.Y == b.Y {
+			// horizontal segment
+			// check if the point in on the line
+			if a.X < b.X {
+				if p.X >= a.X && p.X <= b.X {
+					return rayres{false, true}
+				}
+			} else {
+				if p.X >= b.X && p.X <= a.X {
+					return rayres{false, true}
+				}
 			}
-			if p.X < a.X {
-				return left
+		}
+	}
+	if a.X == b.X && p.X == b.X {
+		// vertical segment
+		// check if the point in on the line
+		if a.Y < b.Y {
+			if p.Y >= a.Y && p.Y <= b.Y {
+				return rayres{false, true}
 			}
 		} else {
-			if p.X >= b.X && p.X <= a.X {
-				return on
-			}
-			if p.X < b.X {
-				return left
+			if p.Y >= b.Y && p.Y <= a.Y {
+				return rayres{false, true}
 			}
 		}
-		return out
+	}
+	if (p.X-a.X)/(b.X-a.X) == (p.Y-a.Y)/(b.Y-a.Y) {
+		return rayres{false, true}
 	}
 
-	if a.X == b.X {
-		// AB is a vertical line.
-		if a.Y > b.Y {
-			// A is above B
-			if p.Y > a.Y || p.Y < b.Y {
-				return out
-			}
-		} else {
-			// B is above A
-			if p.Y > b.Y || p.Y < a.Y {
-				return out
-			}
-		}
-		if p.X == a.X {
-			return on
-		}
-		if p.X < a.X {
-			return left
-		}
-		return out
+	// do the actual raycast here.
+	for p.Y == a.Y || p.Y == b.Y {
+		p.Y = math.Nextafter(p.Y, math.Inf(1))
 	}
-
-	// AB is an angled line
-	if a.Y > b.Y {
-		// swap A and B so that A is below B.
-		a.X, a.Y, b.X, b.Y = b.X, b.Y, a.X, a.Y
-	}
-	if p.Y < a.Y || p.Y > b.Y {
-		return out
-	}
-	if a.X < b.X {
-		if p.X < a.X {
-			return left
-		}
-		if p.X > b.X {
-			return out
+	if a.Y < b.Y {
+		if p.Y < a.Y || p.Y > b.Y {
+			return rayres{false, false}
 		}
 	} else {
-		if p.X < b.X {
-			return left
+		if p.Y < b.Y || p.Y > a.Y {
+			return rayres{false, false}
 		}
+	}
+	if a.X > b.X {
 		if p.X > a.X {
-			return out
+			return rayres{false, false}
+		}
+		if p.X < b.X {
+			return rayres{true, false}
+		}
+	} else {
+		if p.X > b.X {
+			return rayres{false, false}
+		}
+		if p.X < a.X {
+			return rayres{true, false}
 		}
 	}
-	if (p.X == a.X && p.Y == a.Y) || (p.X == b.X && p.Y == b.Y) {
-		// P is on a vertex.
-		return on
+	if a.Y < b.Y {
+		if (p.Y-a.Y)/(p.X-a.X) >= (b.Y-a.Y)/(b.X-a.X) {
+			return rayres{true, false}
+		}
+	} else {
+		if (p.Y-b.Y)/(p.X-b.X) >= (a.Y-b.Y)/(a.X-b.X) {
+			return rayres{true, false}
+		}
 	}
-	v1 := (p.Y - a.Y) / (p.X - a.X)
-	v2 := (b.Y - a.Y) / (b.X - a.X)
-	if v1-v2 == 0 {
-		// P is on a segment
-		return on
-	}
-	if v1 >= v2 {
-		return left
-	}
-	return out
+	return rayres{false, false}
 }
diff --git a/geojson/poly/raycast_test.go b/geojson/poly/raycast_test.go
deleted file mode 100644
index a98861c8..00000000
--- a/geojson/poly/raycast_test.go
+++ /dev/null
@@ -1,66 +0,0 @@
-package poly
-
-import "testing"
-
-func testRayRay(t *testing.T, p, a, b Point, expect rayres) {
-	res := raycast(p, a, b)
-	if res != expect {
-		t.Fatalf("1) %v,%v,%v = %s, expect %s", p, a, b, res, expect)
-	}
-	res = raycast(p, a, b)
-	if res != expect {
-		t.Fatalf("1) %v,%v,%v = %s, expect %s", p, b, a, res, expect)
-	}
-}
-
-func TestRayHorizontal(t *testing.T) {
-	for x := float64(-1); x <= 4+1; x++ {
-		expect := on
-		if x < 0 {
-			expect = left
-		} else if x > 4 {
-			expect = out
-		}
-		testRayRay(t, P(x, 0), P(0, 0), P(4, 0), expect)
-	}
-	for x := float64(-1); x <= 4+1; x++ {
-		expect := out
-		testRayRay(t, P(x, -1), P(0, 0), P(4, 0), expect)
-	}
-	for x := float64(-1); x <= 4+1; x++ {
-		expect := out
-		testRayRay(t, P(x, +1), P(0, 0), P(4, 0), expect)
-	}
-}
-
-func TestRayVertical(t *testing.T) {
-	for y := float64(-1); y <= 4+1; y++ {
-		expect := on
-		if y < 0 || y > 4 {
-			expect = out
-		}
-		testRayRay(t, P(0, y), P(0, 0), P(0, 4), expect)
-	}
-	for y := float64(-1); y <= 4+1; y++ {
-		expect := left
-		if y < 0 || y > 4 {
-			expect = out
-		}
-		testRayRay(t, P(-1, y), P(0, 0), P(0, 4), expect)
-	}
-	for y := float64(-1); y <= 4+1; y++ {
-		expect := out
-		testRayRay(t, P(+1, y), P(0, 0), P(0, 4), expect)
-	}
-}
-
-func TestRayAngled(t *testing.T) {
-	testRayRay(t, P(1, 3), P(0, 4), P(4, 0), on)
-	testRayRay(t, P(0, 4), P(0, 4), P(4, 0), on)
-	testRayRay(t, P(4, 0), P(0, 4), P(4, 0), on)
-	testRayRay(t, P(1, 4), P(0, 4), P(4, 0), out)
-	testRayRay(t, P(5, 0), P(0, 4), P(4, 0), out)
-	testRayRay(t, P(-1, 4), P(0, 4), P(4, 0), left)
-	testRayRay(t, P(3, 0), P(0, 4), P(4, 0), left)
-	testRayRay(t, P(2, 2), P(0, 4), P(4, 0), on)
-}