diff --git a/src/map/datum.cpp b/src/map/datum.cpp
index 3432bf1a..da423e2b 100644
--- a/src/map/datum.cpp
+++ b/src/map/datum.cpp
@@ -46,7 +46,6 @@ static Coordinates molodensky(const Coordinates &c, const Datum &from,
 
 Point3D Datum::helmert(const Point3D &p) const
 {
-	double scale = 1 + _ds * 1e-6;
 	double R00 = 1;
 	double R01 = _rz;
 	double R02 = -_ry;
@@ -57,14 +56,13 @@ Point3D Datum::helmert(const Point3D &p) const
 	double R21 = -_rx;
 	double R22 = 1;
 
-	return Point3D(scale * (R00 * p.x() + R01 * p.y() + R02 * p.z()) + _dx,
-	  scale * (R10 * p.x() + R11 * p.y() + R12 * p.z()) + _dy,
-	  scale * (R20 * p.x() + R21 * p.y() + R22 * p.z()) + _dz);
+	return Point3D(_scale * (R00 * p.x() + R01 * p.y() + R02 * p.z()) + _dx,
+	  _scale * (R10 * p.x() + R11 * p.y() + R12 * p.z()) + _dy,
+	  _scale * (R20 * p.x() + R21 * p.y() + R22 * p.z()) + _dz);
 }
 
 Point3D Datum::helmertr(const Point3D &p) const
 {
-	double scale = 1 + _ds * 1e-6;
 	double R00 = 1;
 	double R01 = _rz;
 	double R02 = -_ry;
@@ -75,9 +73,9 @@ Point3D Datum::helmertr(const Point3D &p) const
 	double R21 = -_rx;
 	double R22 = 1;
 
-	double x = (p.x() - _dx) / scale;
-	double y = (p.y() - _dy) / scale;
-	double z = (p.z() - _dz) / scale;
+	double x = (p.x() - _dx) / _scale;
+	double y = (p.y() - _dy) / _scale;
+	double z = (p.z() - _dz) / _scale;
 
 	return Point3D(R00 * x + R10 * y + R20 * z, R01 * x + R11 * y + R21 * z,
 	  R02 * x + R12 * y + R22 * z);
@@ -86,11 +84,11 @@ Point3D Datum::helmertr(const Point3D &p) const
 Datum::Datum(const Ellipsoid *ellipsoid, double dx, double dy, double dz,
   double rx, double ry, double rz, double ds)
   : _ellipsoid(ellipsoid), _dx(dx), _dy(dy), _dz(dz), _rx(as2rad(rx)),
-  _ry(as2rad(ry)), _rz(as2rad(rz)), _ds(ds)
+  _ry(as2rad(ry)), _rz(as2rad(rz)), _scale(1.0 + ds * 1e-6)
 {
 	if (_ellipsoid->radius() == WGS84_RADIUS && _ellipsoid->flattening()
 	  == WGS84_FLATTENING && _dx == 0.0 && _dy == 0.0 && _dz == 0.0
-	  && _rx == 0.0 && _ry == 0.0 && _rz == 0.0 && _ds == 0.0)
+	  && _rx == 0.0 && _ry == 0.0 && _rz == 0.0 && ds == 0.0)
 		_transformation = None;
 	else
 		_transformation = Helmert;
@@ -98,7 +96,7 @@ Datum::Datum(const Ellipsoid *ellipsoid, double dx, double dy, double dz,
 
 Datum::Datum(const Ellipsoid *ellipsoid, double dx, double dy, double dz)
   : _ellipsoid(ellipsoid), _dx(dx), _dy(dy), _dz(dz), _rx(0.0), _ry(0.0),
-  _rz(0.0), _ds(0.0)
+  _rz(0.0), _scale(1.0)
 {
 	if (_ellipsoid->radius() == WGS84_RADIUS && _ellipsoid->flattening()
 	  == WGS84_FLATTENING && _dx == 0.0 && _dy == 0.0 && _dz == 0.0)
@@ -139,7 +137,7 @@ QDebug operator<<(QDebug dbg, const Datum &datum)
 	dbg.nospace() << "Datum(" << *datum.ellipsoid() << ", " << datum.dx()
 	  << ", " << datum.dy() << ", " << datum.dz() << ", " << rad2as(datum.rx())
 	  << ", " << rad2as(datum.ry()) << ", " << rad2as(datum.rz()) << ", "
-	  << datum.ds() << ")";
+	  << (datum.scale() - 1.0) / 1e-6 << ")";
 	return dbg.space();
 }
 #endif // QT_NO_DEBUG
diff --git a/src/map/datum.h b/src/map/datum.h
index 50889b7f..29aa2708 100644
--- a/src/map/datum.h
+++ b/src/map/datum.h
@@ -11,7 +11,7 @@ class Datum
 {
 public:
 	Datum() : _ellipsoid(0), _transformation(None), _dx(NAN), _dy(NAN),
-	  _dz(NAN), _rx(NAN), _ry(NAN), _rz(NAN), _ds(NAN) {}
+	  _dz(NAN), _rx(NAN), _ry(NAN), _rz(NAN), _scale(NAN) {}
 	Datum(const Ellipsoid *ellipsoid, double dx, double dy, double dz,
 	  double rx, double ry, double rz, double ds);
 	Datum(const Ellipsoid *ellipsoid, double dx, double dy, double dz);
@@ -20,16 +20,16 @@ public:
 	double dx() const {return _dx;}
 	double dy() const {return _dy;}
 	double dz() const {return _dz;}
-	double ds() const {return _ds;}
 	double rx() const {return _rx;}
 	double ry() const {return _ry;}
 	double rz() const {return _rz;}
+	double scale() const {return _scale;}
 
 	bool isNull() const
 	  {return !_ellipsoid;}
 	bool isValid() const
 	  {return (_ellipsoid && !std::isnan(_dx) && !std::isnan(_dy)
-		&& !std::isnan(_dz) && !std::isnan(_ds) && !std::isnan(_rx)
+		&& !std::isnan(_dz) && !std::isnan(_scale) && !std::isnan(_rx)
 		&& !std::isnan(_ry) && !std::isnan(_rz));}
 
 	Coordinates toWGS84(const Coordinates &c) const;
@@ -47,13 +47,13 @@ private:
 
 	const Ellipsoid *_ellipsoid;
 	TransformationType _transformation;
-	double _dx, _dy, _dz, _rx, _ry, _rz, _ds;
+	double _dx, _dy, _dz, _rx, _ry, _rz, _scale;
 };
 
 inline bool operator==(const Datum &d1, const Datum &d2)
   {return (*d1.ellipsoid() == *d2.ellipsoid() && d1.dx() == d2.dx()
 	&& d1.dy() == d2.dy() && d1.dz() == d2.dz() && d1.rx() == d2.rx()
-	&& d1.ry() == d2.ry() && d1.rz() == d2.rz() && d1.ds() == d2.ds());}
+	&& d1.ry() == d2.ry() && d1.rz() == d2.rz() && d1.scale() == d2.scale());}
 
 #ifndef QT_NO_DEBUG
 QDebug operator<<(QDebug dbg, const Datum &datum);