diff --git a/gpxsee.pro b/gpxsee.pro
index 2ad5a6fb..40c72107 100644
--- a/gpxsee.pro
+++ b/gpxsee.pro
@@ -83,7 +83,8 @@ HEADERS += src/config.h \
     src/offlinemap.h \
     src/mapdir.h \
     src/matrix.h \
-    src/tar.h
+    src/tar.h \
+    src/atlas.h
 SOURCES += src/main.cpp \
     src/gui.cpp \
     src/poi.cpp \
@@ -142,7 +143,8 @@ SOURCES += src/main.cpp \
     src/offlinemap.cpp \
     src/mapdir.cpp \
     src/matrix.cpp \
-    src/tar.cpp
+    src/tar.cpp \
+    src/atlas.cpp
 RESOURCES += gpxsee.qrc
 TRANSLATIONS = lang/gpxsee_cs.ts \
     lang/gpxsee_sv.ts
diff --git a/src/atlas.cpp b/src/atlas.cpp
new file mode 100644
index 00000000..38f5c157
--- /dev/null
+++ b/src/atlas.cpp
@@ -0,0 +1,261 @@
+#include <QDir>
+#include <QtAlgorithms>
+#include <QPainter>
+#include "tar.h"
+#include "atlas.h"
+
+
+#define ZOOM_THRESHOLD 0.9
+
+#define TL(m) ((m)->xy2ll((m)->bounds().topLeft()))
+#define BR(m) ((m)->xy2ll((m)->bounds().bottomRight()))
+
+static bool resCmp(const OfflineMap *m1, const OfflineMap *m2)
+{
+	qreal r1, r2;
+
+	r1 = m1->resolution(m1->bounds().center());
+	r2 = m2->resolution(m2->bounds().center());
+
+	return r1 > r2;
+}
+
+static bool lonCmp(const OfflineMap *m1, const OfflineMap *m2)
+{
+	return TL(m1).lon() < TL(m2).lon();
+}
+
+static bool latCmp(const OfflineMap *m1, const OfflineMap *m2)
+{
+	return TL(m1).lat() > TL(m2).lat();
+}
+
+bool Atlas::isAtlas(const QFileInfoList &files)
+{
+	for (int i = 0; i < files.count(); i++) {
+		const QString &fileName = files.at(i).fileName();
+		if (fileName.endsWith(".tar")) {
+			Tar tar;
+			if (!tar.load(files.at(i).absoluteFilePath())) {
+				qWarning("%s: %s: error loading tar file", qPrintable(_name),
+				  qPrintable(fileName));
+				return false;
+			}
+			QStringList tarFiles = tar.files();
+			for (int j = 0; j < tarFiles.size(); j++)
+				if (tarFiles.at(j).endsWith(".tba"))
+					return true;
+		} else if (fileName.endsWith(".tba"))
+			return true;
+	}
+
+	return false;
+}
+
+void Atlas::computeZooms()
+{
+	qSort(_maps.begin(), _maps.end(), resCmp);
+
+	_zooms.append(QPair<int, int>(0, _maps.count() - 1));
+	for (int i = 1; i < _maps.count(); i++) {
+		qreal last = _maps.at(i-1)->resolution(_maps.at(i)->bounds().center());
+		qreal cur = _maps.at(i)->resolution(_maps.at(i)->bounds().center());
+		if (cur < last * ZOOM_THRESHOLD) {
+			_zooms.last().second = i-1;
+			_zooms.append(QPair<int, int>(i, _maps.count() - 1));
+		}
+	}
+}
+
+void Atlas::computeBounds()
+{
+	QList<QPointF> offsets;
+
+	for (int i = 0; i < _maps.count(); i++)
+		offsets.append(QPointF());
+
+	for (int z = 0; z < _zooms.count(); z++) {
+		qreal w = 0, h = 0;
+
+		QList<OfflineMap*> m;
+		for (int i = _zooms.at(z).first; i <= _zooms.at(z).second; i++)
+			m.append(_maps.at(i));
+
+		qSort(m.begin(), m.end(), lonCmp);
+		offsets[_maps.indexOf(m.first())].setX(w);
+		for (int i = 1; i < m.size(); i++) {
+			if (TL(m.at(i)).lon() > TL(m.at(i-1)).lon()) {
+				w += m.at(i-1)->ll2xy(Coordinates(TL(m.at(i)).lon(),
+				  TL(m.at(i-1)).lat())).x() - m.at(i-1)->bounds().left();
+				offsets[_maps.indexOf(m.at(i))].setX(round(w));
+			}
+		}
+
+		qSort(m.begin(), m.end(), latCmp);
+		offsets[_maps.indexOf(m.first())].setY(h);
+		for (int i = 1; i < m.size(); i++) {
+			if (TL(m.at(i)).lat() < TL(m.at(i-1)).lat()) {
+				h += m.at(i-1)->ll2xy(Coordinates(TL(m.at(i-1)).lon(),
+				  TL(m.at(i)).lat())).y() - m.at(i-1)->bounds().top();
+				offsets[_maps.indexOf(m.at(i))].setY(round(h));
+			}
+		}
+	}
+
+	for (int i = 0; i < _maps.count(); i++)
+		_bounds.append(QPair<QRectF, QRectF>(QRectF(TL(_maps.at(i)).toPointF(),
+		  BR(_maps.at(i)).toPointF()), QRectF(offsets.at(i),
+		  _maps.at(i)->bounds().size())));
+}
+
+Atlas::Atlas(const QString &path, QObject *parent) : Map(parent)
+{
+	_valid = false;
+
+	QFileInfo fi(path);
+	_name = fi.fileName();
+
+	QDir dir(path);
+	QFileInfoList files = dir.entryInfoList(QDir::Files);
+	if (!isAtlas(files))
+		return;
+
+	QFileInfoList layers = dir.entryInfoList(QDir::Dirs | QDir::NoDotAndDotDot);
+	for (int n = 0; n < layers.count(); n++) {
+		QDir zdir(layers.at(n).absoluteFilePath());
+		QFileInfoList maps = zdir.entryInfoList(QDir::Dirs
+		  | QDir::NoDotAndDotDot);
+		for (int i = 0; i < maps.count(); i++) {
+			OfflineMap *map = new OfflineMap(maps.at(i).absoluteFilePath());
+			if (map->isValid())
+				_maps.append(map);
+		}
+	}
+	if (_maps.isEmpty()) {
+		qWarning("%s: No usable maps available", qPrintable(_name));
+		return;
+	}
+
+	computeZooms();
+	computeBounds();
+
+	_zoom = 0;
+	_valid = true;
+}
+
+QRectF Atlas::bounds() const
+{
+	QSizeF s(0, 0);
+
+	for (int i = _zooms.at(_zoom).first; i <= _zooms.at(_zoom).second; i++) {
+		if (_bounds.at(i).second.right() > s.width())
+			s.setWidth(_bounds.at(i).second.right());
+		if (_bounds.at(i).second.bottom() > s.height())
+			s.setHeight(_bounds.at(i).second.bottom());
+	}
+
+	return QRectF(QPointF(0, 0), s);
+}
+
+qreal Atlas::resolution(const QPointF &p) const
+{
+	int idx = _zooms.at(_zoom).first;
+
+	for (int i = _zooms.at(_zoom).first; i <= _zooms.at(_zoom).second; i++) {
+		if (_bounds.at(i).second.contains(p)) {
+			idx = i;
+			break;
+		}
+	}
+
+	return _maps.at(idx)->resolution(p);
+}
+
+qreal Atlas::zoom() const
+{
+	return _zoom;
+}
+
+qreal Atlas::zoomFit(const QSize &size, const QRectF &br)
+{
+	_zoom = 0;
+
+	for (int z = 0; z < _zooms.count(); z++) {
+		for (int i = _zooms.at(z).first; i <= _zooms.at(z).second; i++) {
+			if (_bounds.at(i).first.contains(br.center()))
+				continue;
+
+			QRect sbr = QRectF(_maps.at(i)->ll2xy(br.topLeft()),
+			  _maps.at(i)->ll2xy(br.bottomRight())).toRect().normalized();
+
+			if (sbr.size().width() > size.width()
+			  || sbr.size().height() > size.height())
+				return _zoom;
+
+			_zoom = z;
+			break;
+		}
+	}
+
+	return _zoom;
+}
+
+qreal Atlas::zoomIn()
+{
+	_zoom = qMin(_zoom + 1, _zooms.size() - 1);
+	return _zoom;
+}
+
+qreal Atlas::zoomOut()
+{
+	_zoom = qMax(_zoom - 1, 0);
+	return _zoom;
+}
+
+QPointF Atlas::ll2xy(const Coordinates &c) const
+{
+	int idx = _zooms.at(_zoom).first;
+
+	for (int i = _zooms.at(_zoom).first; i <= _zooms.at(_zoom).second; i++) {
+		if (_bounds.at(i).first.contains(c.lon(), c.lat())) {
+			idx = i;
+			break;
+		}
+	}
+
+	QPointF p = _maps.at(idx)->ll2xy(c);
+	return p + _bounds.at(idx).second.topLeft();
+}
+
+Coordinates Atlas::xy2ll(const QPointF &p) const
+{
+	int idx = _zooms.at(_zoom).first;
+
+	for (int i = _zooms.at(_zoom).first; i <= _zooms.at(_zoom).second; i++) {
+		if (_bounds.at(i).second.contains(p)) {
+			idx = i;
+			break;
+		}
+	}
+
+	QPointF p2 = p - _bounds.at(idx).second.topLeft();
+	return _maps.at(idx)->xy2ll(p2);
+}
+
+void Atlas::draw(QPainter *painter, const QRectF &rect)
+{
+	painter->fillRect(rect, Qt::white);
+
+	for (int i = _zooms.at(_zoom).first; i <= _zooms.at(_zoom).second; i++) {
+		if (rect.intersects(_bounds.at(i).second)) {
+			OfflineMap *map = _maps.at(i);
+			QRectF ir = rect.intersected(_bounds.at(i).second);
+			const QPointF offset = _bounds.at(i).second.topLeft();
+			QRectF pr = QRectF(ir.topLeft() - offset, ir.size());
+
+			painter->translate(offset);
+			map->draw(painter, pr);
+			painter->translate(-offset);
+		}
+	}
+}
diff --git a/src/atlas.h b/src/atlas.h
new file mode 100644
index 00000000..e5307c58
--- /dev/null
+++ b/src/atlas.h
@@ -0,0 +1,47 @@
+#ifndef ATLAS_H
+#define ATLAS_H
+
+#include <QFileInfoList>
+#include "map.h"
+#include "offlinemap.h"
+
+
+class Atlas : public Map
+{
+	Q_OBJECT
+
+public:
+	Atlas(const QString &path, QObject *parent = 0);
+
+	const QString &name() const {return _name;}
+
+	QRectF bounds() const;
+	qreal resolution(const QPointF &p) const;
+
+	qreal zoom() const;
+	qreal zoomFit(const QSize &size, const QRectF &br);
+	qreal zoomIn();
+	qreal zoomOut();
+
+	QPointF ll2xy(const Coordinates &c) const;
+	Coordinates xy2ll(const QPointF &p) const;
+
+	void draw(QPainter *painter, const QRectF &rect);
+
+	bool isValid() {return _valid;}
+
+private:
+	bool isAtlas(const QFileInfoList &files);
+	void computeZooms();
+	void computeBounds();
+
+	QString _name;
+	bool _valid;
+
+	QList<OfflineMap*> _maps;
+	QVector<QPair<int, int> > _zooms;
+	QVector<QPair<QRectF, QRectF> > _bounds;
+	int _zoom;
+};
+
+#endif // ATLAS_H
diff --git a/src/coordinates.h b/src/coordinates.h
index 9437bc28..1251fe90 100644
--- a/src/coordinates.h
+++ b/src/coordinates.h
@@ -32,6 +32,8 @@ public:
 	QPointF toMercator() const;
 	static Coordinates fromMercator(const QPointF &m);
 
+	QPointF toPointF() const {return QPointF(_lon, _lat);}
+
 private:
 	qreal _lat, _lon;
 };
diff --git a/src/mapdir.cpp b/src/mapdir.cpp
index aeca2be3..11efdc39 100644
--- a/src/mapdir.cpp
+++ b/src/mapdir.cpp
@@ -1,8 +1,7 @@
 #include <QDir>
-#include "mapdir.h"
-
-#include <QDebug>
+#include "atlas.h"
 #include "offlinemap.h"
+#include "mapdir.h"
 
 QList<Map*> MapDir::load(const QString &path, QObject *parent)
 {
@@ -21,11 +20,20 @@ QList<Map*> MapDir::load(const QString &path, QObject *parent)
 	QFileInfoList list = dir.entryInfoList(QDir::Dirs | QDir::NoDotAndDotDot);
 	for (int i = 0; i < list.size(); i++) {
 		QFileInfo fileInfo = list.at(i);
-		OfflineMap *map = new OfflineMap(fileInfo.absoluteFilePath(), parent);
-		if (map->isValid())
-			maps.append(map);
-		else
-			delete map;
+
+		Atlas *atlas = new Atlas(fileInfo.absoluteFilePath(), parent);
+		if (atlas->isValid())
+			maps.append(atlas);
+		else {
+			delete atlas;
+
+			OfflineMap *map = new OfflineMap(fileInfo.absoluteFilePath(),
+			  parent);
+			if (map->isValid())
+				maps.append(map);
+			else
+				delete map;
+		}
 	}
 
 	return maps;
diff --git a/src/offlinemap.cpp b/src/offlinemap.cpp
index 40a62cf9..aa4832c5 100644
--- a/src/offlinemap.cpp
+++ b/src/offlinemap.cpp
@@ -353,7 +353,8 @@ void OfflineMap::draw(QPainter *painter, const QRectF &rect)
 					if (!QPixmapCache::find(key, &pixmap)) {
 						QByteArray ba = _tar.file(tileName);
 						pixmap = QPixmap::fromImage(QImage::fromData(ba));
-						QPixmapCache::insert(key, pixmap);
+						if (!pixmap.isNull())
+							QPixmapCache::insert(key, pixmap);
 					}
 				} else
 					pixmap = QPixmap(tileName);
diff --git a/src/tar.cpp b/src/tar.cpp
index 4a08d5ca..f4346e0b 100644
--- a/src/tar.cpp
+++ b/src/tar.cpp
@@ -26,7 +26,7 @@ struct Header
 	char devmajor[8];             /* 329 */
 	char devminor[8];             /* 337 */
 	char prefix[155];             /* 345 */
-								  /* 500 */
+	                              /* 500 */
 };
 
 static quint64 number(const char* data, size_t size)
@@ -65,7 +65,8 @@ bool Tar::load(const QString &path)
 QByteArray Tar::file(const QString &name)
 {
 	QMap<QString, Tar::Info>::const_iterator it = _index.find(name);
-	Q_ASSERT(it != _index.end());
+	if (it == _index.end())
+		return QByteArray();
 
 	if (_file.seek(it.value().offset()))
 		return _file.read(it.value().size());