diff --git a/genlib/p2dpoly.h b/genlib/p2dpoly.h
index 38c3716d..e1b84338 100644
--- a/genlib/p2dpoly.h
+++ b/genlib/p2dpoly.h
@@ -33,17 +33,17 @@
 enum { NOAXIS = -1, XAXIS = 0, YAXIS = 1 };
 
 class Point2f;
-bool approxeq(const Point2f &p1, const Point2f &p2, double tolerance = 0.0);
+bool approxeq(const Point2f &p1, const Point2f &p2, double tolerance = 1e-9);
 class QtRegion;
-bool intersect_region(const QtRegion &a, const QtRegion &b, double tolerance = 0.0);
-bool overlap_x(const QtRegion &a, const QtRegion &b, double tolerance = 0.0);
-bool overlap_y(const QtRegion &a, const QtRegion &b, double tolerance = 0.0);
+bool intersect_region(const QtRegion &a, const QtRegion &b, double tolerance = 1e-9);
+bool overlap_x(const QtRegion &a, const QtRegion &b, double tolerance = 1e-9);
+bool overlap_y(const QtRegion &a, const QtRegion &b, double tolerance = 1e-9);
 class Line;
-bool intersect_line(const Line &a, const Line &b, double tolerance = 0.0);
-bool intersect_line_no_touch(const Line &a, const Line &b, double tolerance = 0.0);
-int intersect_line_distinguish(const Line &a, const Line &b, double tolerance = 0.0);
-int intersect_line_b(const Line &a, const Line &b, double tolerance = 0.0);
-Point2f intersection_point(const Line &a, const Line &b, double tolerance = 0.0);
+bool intersect_line(const Line &a, const Line &b, double tolerance = 1e-9);
+bool intersect_line_no_touch(const Line &a, const Line &b, double tolerance = 1e-9);
+int intersect_line_distinguish(const Line &a, const Line &b, double tolerance = 1e-9);
+int intersect_line_b(const Line &a, const Line &b, double tolerance = 1e-9);
+Point2f intersection_point(const Line &a, const Line &b, double tolerance = 1e-9);
 
 // NaN on Intel:
 // Quick mod - TV
@@ -109,7 +109,7 @@ class Point2f {
     friend Point2f pointfromangle(double angle);
     // a couple of useful tests
     bool intriangle(const Point2f &p1, const Point2f &p2, const Point2f &p3);
-    bool insegment(const Point2f &key, const Point2f &p2, const Point2f &p3, double tolerance = 0.0);
+    bool insegment(const Point2f &key, const Point2f &p2, const Point2f &p3, double tolerance = 1e-9);
     // for OS transformation (note: accurate only to 5 metres according to OS)
     Point2f longlat2os(const Point2f &p);
 
diff --git a/salalib/shapemap.h b/salalib/shapemap.h
index 01847716..5bce75d4 100644
--- a/salalib/shapemap.h
+++ b/salalib/shapemap.h
@@ -399,8 +399,8 @@ class ShapeMap : public PixelBase {
     bool pointInPoly(const Point2f &p, int shaperef) const;
     // retrieve lists of polys point intersects:
     std::vector<int> pointInPolyList(const Point2f &p) const;
-    std::vector<int> lineInPolyList(const Line &li, size_t lineref = -1, double tolerance = 0.0) const;
-    std::vector<int> polyInPolyList(int polyref, double tolerance = 0.0) const;
+    std::vector<int> lineInPolyList(const Line &li, size_t lineref = -1, double tolerance = 1e-9) const;
+    std::vector<int> polyInPolyList(int polyref, double tolerance = 1e-9) const;
     std::vector<int> shapeInPolyList(const SalaShape &shape);
     // helper to make actual test of point in shape:
     int testPointInPoly(const Point2f &p, const ShapeRef &shape) const;
diff --git a/salalib/spacepix.h b/salalib/spacepix.h
index 807f7dff..015bfba1 100644
--- a/salalib/spacepix.h
+++ b/salalib/spacepix.h
@@ -131,8 +131,8 @@ class SpacePixel : public PixelBase {
     virtual bool findNextLine(bool &) const;
     virtual const Line &getNextLine() const;
     //
-    bool intersect(const Line &l, double tolerance = 0.0);
-    bool intersect_exclude(const Line &l, double tolerance = 0.0);
+    bool intersect(const Line &l, double tolerance = 1e-9);
+    bool intersect_exclude(const Line &l, double tolerance = 1e-9);
 
     void cutLine(Line &l, short dir);