diff --git a/libraries/AP_Math/examples/polygon/polygon.pde b/libraries/AP_Math/examples/polygon/polygon.pde
index cf2352f23b..13260f868b 100644
--- a/libraries/AP_Math/examples/polygon/polygon.pde
+++ b/libraries/AP_Math/examples/polygon/polygon.pde
@@ -43,90 +43,21 @@ static const struct {
     { Vector2l(-266435650, 1518313540), false },
     { Vector2l(-266435690, 1518303530), false },
     { Vector2l(-266435690, 1518303490), true },
+    { Vector2l(-265875990, 1518344049), true },
+    { Vector2l(-265875990, 1518344051), false },
+    { Vector2l(-266454781, 1518820530), true },
+    { Vector2l(-266454779, 1518820530), true },
+    { Vector2l(-266092109, 1518747420), true },
+    { Vector2l(-266092111, 1518747420), false },
+    { Vector2l(-266092110, 1518747421), true },
+    { Vector2l(-266092110, 1518747419), false },
+    { Vector2l(-266092111, 1518747421), true },
+    { Vector2l(-266092109, 1518747421), true },
+    { Vector2l(-266092111, 1518747419), false },
 };
 
 #define ARRAY_LENGTH(x) (sizeof((x))/sizeof((x)[0]))
 
-static float point_distance(Vector2l &p1, Vector2l &p2)
-{
-	float rads 			= (fabs(p1.x)*1.0e-7) * 0.0174532925;
-	float lng_scale		= cos(rads);
-
-	float dlat 		= (float)(p1.x - p2.x);
-	float dlong		= ((float)(p1.y - p2.y)) * lng_scale;
-	return sqrt((dlat*dlat) + (dlong*dlong)) * .01113195;
-}
-
-/*
-  test precision of the calculation 
- */
-static void precision_test(void)
-{
-    Vector2l p1, p2, p;
-    float r;
-    int32_t dx, dy;
-    float worst_precision = 0.0;
-    const float delta = 0.5;
-    const float base = 0.9;
-
-    Serial.println("Precision test:");
-
-    p1 = OBC_boundary[8];
-    p2 = OBC_boundary[10];
-    dx = p2.x - p1.x;
-    dy = p2.y - p1.y;
-    
-    // first come from the left
-    for (r=-base; r<0.0; r *= delta) {
-        p.x = p1.x + r*dx;
-        p.y = p1.y + r*dy;
-        if (!Polygon_outside(p, OBC_boundary, ARRAY_LENGTH(OBC_boundary))) {
-            float precision = point_distance(p, p1);
-            if (precision > worst_precision) {
-                worst_precision = precision;
-            }
-        }
-    }
-
-    // in the middle
-    for (r=base; r>0.0; r *= delta) {
-        p.x = p1.x + r*dx;
-        p.y = p1.y + r*dy;
-        if (Polygon_outside(p, OBC_boundary, ARRAY_LENGTH(OBC_boundary))) {
-            float precision = point_distance(p, p1);
-            if (precision > worst_precision) {
-                worst_precision = precision;
-            }
-        }
-    }
-
-    // from the left on other side
-    for (r=-base; r<0.0; r *= delta) {
-        p.x = p2.x + r*dx;
-        p.y = p2.y + r*dy;
-        if (Polygon_outside(p, OBC_boundary, ARRAY_LENGTH(OBC_boundary))) {
-            float precision = point_distance(p, p2);
-            if (precision > worst_precision) {
-                worst_precision = precision;
-            }
-        }
-    }
-
-    // from the right 
-    for (r=base; r>0.0; r *= delta) {
-        p.x = p2.x + r*dx;
-        p.y = p2.y + r*dy;
-        if (!Polygon_outside(p, OBC_boundary, ARRAY_LENGTH(OBC_boundary))) {
-            float precision = point_distance(p, p2);
-            if (precision > worst_precision) {
-                worst_precision = precision;
-            }
-        }
-    }
-
-    Serial.printf_P(PSTR("worst precision: %f meters\n"), worst_precision);
-}
-
 /*
   polygon tests
  */
@@ -163,8 +94,6 @@ void setup(void)
     }
     Serial.println(all_passed?"TEST PASSED":"TEST FAILED");
 
-    precision_test();
-
     Serial.println("Speed test:");
     start_time = micros();
     for (count=0; count<1000; count++) {
diff --git a/libraries/AP_Math/polygon.cpp b/libraries/AP_Math/polygon.cpp
index 0cc3bdb81f..0312a73fe8 100644
--- a/libraries/AP_Math/polygon.cpp
+++ b/libraries/AP_Math/polygon.cpp
@@ -43,19 +43,33 @@ bool Polygon_outside(const Vector2l &P, const Vector2l *V, unsigned n)
         if ((V[i].y > P.y) == (V[j].y > P.y)) {
             continue;
         }
-        float dx1, dx2, dy1, dy2;
-        // use floating point to cope with possible integer overflow
-        // this still results in precision of better than 1m
+        int32_t dx1, dx2, dy1, dy2;
         dx1 = P.x - V[i].x;
         dx2 = V[j].x - V[i].x;
         dy1 = P.y - V[i].y;
         dy2 = V[j].y - V[i].y;
+        int8_t dx1s, dx2s, dy1s, dy2s, m1, m2;
+#define sign(x) ((x)<0?-1:1)
+        dx1s = sign(dx1);
+        dx2s = sign(dx2);
+        dy1s = sign(dy1);
+        dy2s = sign(dy2);
+        m1 = dx1s * dy2s;
+        m2 = dx2s * dy1s;
         if (dy2 < 0) {
-            if ( dx1 * dy2 > dx2 * dy1 ) {
+            if (m1 > m2) {
+                outside = !outside;
+            } else if (m1 < m2) {
+                continue;
+            } else if ( dx1 * (int64_t)dy2 > dx2 * (int64_t)dy1 ) {
                 outside = !outside;
             }
         } else {
-            if ( dx1 * dy2 < dx2 * dy1 ) {
+            if (m1 < m2) {
+                outside = !outside;
+            } else if (m1 > m2) {
+                continue;
+            } else if ( dx1 * (int64_t)dy2 < dx2 * (int64_t)dy1 ) {
                 outside = !outside;
             }
         }