diff --git a/src/atlas.cpp b/src/atlas.cpp
index 8a1654b2..6ceeffe2 100644
--- a/src/atlas.cpp
+++ b/src/atlas.cpp
@@ -118,6 +118,7 @@ Atlas::Atlas(const QString &fileName, QObject *parent) : Map(parent)
 	_valid = false;
 	_zoom = 0;
 	_name = fi.dir().dirName();
+	_ci = -1; _cz = -1;
 
 	if (!isAtlas(tar, fileName))
 		return;
@@ -233,35 +234,33 @@ qreal Atlas::zoomOut()
 	return _zoom;
 }
 
-QPointF Atlas::ll2xy(const Coordinates &c) const
+QPointF Atlas::ll2xy(const Coordinates &c)
 {
-	static int idx = -1;
-	static int zoom = -1;
 	QPointF pp;
 
-	if (zoom != _zoom) {
-		idx = -1;
-		zoom = _zoom;
+	if (_cz != _zoom) {
+		_ci = -1;
+		_cz = _zoom;
 	}
 
-	if (idx >= 0)
-		pp = _maps.at(idx)->ll2pp(c);
-	if (idx < 0 || !_bounds.at(idx).first.contains(pp)) {
-		idx = _zooms.at(zoom).first;
-		for (int i = _zooms.at(zoom).first; i <= _zooms.at(zoom).second; i++) {
+	if (_ci >= 0)
+		pp = _maps.at(_ci)->ll2pp(c);
+	if (_ci < 0 || !_bounds.at(_ci).first.contains(pp)) {
+		_ci = _zooms.at(_zoom).first;
+		for (int i = _zooms.at(_zoom).first; i <= _zooms.at(_zoom).second; i++) {
 			pp = _maps.at(i)->ll2pp(c);
 			if (_bounds.at(i).first.contains(pp)) {
-				idx = i;
+				_ci = i;
 				break;
 			}
 		}
 	}
 
-	QPointF p = _maps.at(idx)->pp2xy(pp);
-	return p + _bounds.at(idx).second.topLeft();
+	QPointF p = _maps.at(_ci)->pp2xy(pp);
+	return p + _bounds.at(_ci).second.topLeft();
 }
 
-Coordinates Atlas::xy2ll(const QPointF &p) const
+Coordinates Atlas::xy2ll(const QPointF &p)
 {
 	int idx = _zooms.at(_zoom).first;
 
diff --git a/src/atlas.h b/src/atlas.h
index 871be6b0..80b8f6b6 100644
--- a/src/atlas.h
+++ b/src/atlas.h
@@ -24,8 +24,8 @@ public:
 	qreal zoomIn();
 	qreal zoomOut();
 
-	QPointF ll2xy(const Coordinates &c) const;
-	Coordinates xy2ll(const QPointF &p) const;
+	QPointF ll2xy(const Coordinates &c);
+	Coordinates xy2ll(const QPointF &p);
 
 	void draw(QPainter *painter, const QRectF &rect);
 
@@ -48,6 +48,8 @@ private:
 	QVector<QPair<int, int> > _zooms;
 	QVector<QPair<QRectF, QRectF> > _bounds;
 	int _zoom;
+
+	int _ci, _cz;
 };
 
 #endif // ATLAS_H
diff --git a/src/emptymap.cpp b/src/emptymap.cpp
index 71355584..681b2d39 100644
--- a/src/emptymap.cpp
+++ b/src/emptymap.cpp
@@ -64,13 +64,13 @@ void EmptyMap::draw(QPainter *painter, const QRectF &rect)
 	painter->fillRect(rect, Qt::white);
 }
 
-QPointF EmptyMap::ll2xy(const Coordinates &c) const
+QPointF EmptyMap::ll2xy(const Coordinates &c)
 {
 	QPointF m = Mercator().ll2xy(c);
 	return QPointF(m.x() / _scale, m.y() / -_scale);
 }
 
-Coordinates EmptyMap::xy2ll(const QPointF &p) const
+Coordinates EmptyMap::xy2ll(const QPointF &p)
 {
 	QPointF m(p.x() * _scale, -p.y() * _scale);
 	return Mercator().xy2ll(m);
diff --git a/src/emptymap.h b/src/emptymap.h
index 2efd10c7..0ccf3fce 100644
--- a/src/emptymap.h
+++ b/src/emptymap.h
@@ -20,8 +20,8 @@ public:
 	qreal zoomIn();
 	qreal zoomOut();
 
-	QPointF ll2xy(const Coordinates &c) const;
-	Coordinates xy2ll(const QPointF &p) const;
+	QPointF ll2xy(const Coordinates &c);
+	Coordinates xy2ll(const QPointF &p);
 
 	void draw(QPainter *painter, const QRectF &rect);
 
diff --git a/src/map.h b/src/map.h
index 77b6f37e..add0db07 100644
--- a/src/map.h
+++ b/src/map.h
@@ -25,8 +25,8 @@ public:
 	virtual qreal zoomIn() = 0;
 	virtual qreal zoomOut() = 0;
 
-	virtual QPointF ll2xy(const Coordinates &c) const = 0;
-	virtual Coordinates xy2ll(const QPointF &p) const = 0;
+	virtual QPointF ll2xy(const Coordinates &c) = 0;
+	virtual Coordinates xy2ll(const QPointF &p) = 0;
 
 	virtual void draw(QPainter *painter, const QRectF &rect) = 0;
 
diff --git a/src/offlinemap.h b/src/offlinemap.h
index 7170b527..a89ce503 100644
--- a/src/offlinemap.h
+++ b/src/offlinemap.h
@@ -31,9 +31,9 @@ public:
 	qreal zoomIn() {return 1.0;}
 	qreal zoomOut() {return 1.0;}
 
-	QPointF ll2xy(const Coordinates &c) const
+	QPointF ll2xy(const Coordinates &c)
 	  {return _transform.map(_projection->ll2xy(c));}
-	Coordinates xy2ll(const QPointF &p) const
+	Coordinates xy2ll(const QPointF &p)
 	  {return _projection->xy2ll(_inverted.map(p));}
 
 	void draw(QPainter *painter, const QRectF &rect);
diff --git a/src/onlinemap.cpp b/src/onlinemap.cpp
index 5cff4dea..94daecf2 100644
--- a/src/onlinemap.cpp
+++ b/src/onlinemap.cpp
@@ -232,13 +232,13 @@ void OnlineMap::draw(QPainter *painter, const QRectF &rect)
 	}
 }
 
-QPointF OnlineMap::ll2xy(const Coordinates &c) const
+QPointF OnlineMap::ll2xy(const Coordinates &c)
 {
 	QPointF m = Mercator().ll2xy(c);
 	return QPointF(m.x() / _scale, m.y() / -_scale);
 }
 
-Coordinates OnlineMap::xy2ll(const QPointF &p) const
+Coordinates OnlineMap::xy2ll(const QPointF &p)
 {
 	QPointF m(p.x() * _scale, -p.y() * _scale);
 	return Mercator().xy2ll(m);
diff --git a/src/onlinemap.h b/src/onlinemap.h
index 22b40553..94d967d5 100644
--- a/src/onlinemap.h
+++ b/src/onlinemap.h
@@ -23,8 +23,8 @@ public:
 	qreal zoomIn();
 	qreal zoomOut();
 
-	QPointF ll2xy(const Coordinates &c) const;
-	Coordinates xy2ll(const QPointF &p) const;
+	QPointF ll2xy(const Coordinates &c);
+	Coordinates xy2ll(const QPointF &p);
 
 	void draw(QPainter *painter, const QRectF &rect);