diff --git a/src/data/dem.cpp b/src/data/dem.cpp
index ed5f6d84..16a2b162 100644
--- a/src/data/dem.cpp
+++ b/src/data/dem.cpp
@@ -4,13 +4,13 @@
 #include "common/coordinates.h"
 #include "dem.h"
 
+
 #define SRTM3_SAMPLES 1201
 #define SRTM1_SAMPLES 3601
 
 #define SRTM_SIZE(samples) \
 	((samples) * (samples) * 2)
 
-
 static qreal interpolate(qreal dx, qreal dy, qreal p0, qreal p1, qreal p2,
   qreal p3)
 {
@@ -18,21 +18,21 @@ static qreal interpolate(qreal dx, qreal dy, qreal p0, qreal p1, qreal p2,
 	  + p3 * dx * dy;
 }
 
-static qreal value(int col, int row, int samples, const QByteArray data)
+static qreal value(int col, int row, int samples, const QByteArray *data)
 {
 	int pos = ((samples - 1 - row) * samples + col) * 2;
-	qint16 val = qFromBigEndian(*((const qint16*)(data.constData() + pos)));
+	qint16 val = qFromBigEndian(*((const qint16*)(data->constData() + pos)));
 
 	return (val == -32768) ? NAN : val;
 }
 
-static qreal height(const Coordinates &c, const QByteArray data)
+static qreal height(const Coordinates &c, const QByteArray *data)
 {
 	int samples;
 
-	if (data.size() == SRTM_SIZE(SRTM3_SAMPLES))
+	if (data->size() == SRTM_SIZE(SRTM3_SAMPLES))
 		samples = SRTM3_SAMPLES;
-	else if (data.size() == SRTM_SIZE(SRTM1_SAMPLES))
+	else if (data->size() == SRTM_SIZE(SRTM1_SAMPLES))
 		samples = SRTM1_SAMPLES;
 	else
 		return NAN;
@@ -52,16 +52,16 @@ static qreal height(const Coordinates &c, const QByteArray data)
 
 
 QString DEM::_dir;
-QMap<DEM::Key, QByteArray> DEM::_data;
+QCache<DEM::Key, QByteArray> DEM::_data;
 
 QString DEM::fileName(const Key &key)
 {
-	const char ns = (key.lat >= 0) ? 'N' : 'S';
-	const char ew = (key.lon >= 0) ? 'E' : 'W';
+	const char ns = (key.lat() >= 0) ? 'N' : 'S';
+	const char ew = (key.lon() >= 0) ? 'E' : 'W';
 
 	QString basename = QString("%1%2%3%4.hgt").arg(ns)
-	  .arg(qAbs(key.lat), 2, 10, QChar('0')).arg(ew)
-	  .arg(qAbs(key.lon), 3, 10, QChar('0'));
+	  .arg(qAbs(key.lat()), 2, 10, QChar('0')).arg(ew)
+	  .arg(qAbs(key.lon()), 3, 10, QChar('0'));
 	return QDir(_dir).absoluteFilePath(basename);
 }
 
@@ -77,18 +77,19 @@ qreal DEM::elevation(const Coordinates &c)
 
 	Key k((int)c.lon(), (int)c.lat());
 
-	QMap<Key, QByteArray>::const_iterator it(_data.find(k));
-	if (it == _data.constEnd()) {
+	QByteArray *ba = _data[k];
+	if (!ba) {
 		QFile file(fileName(k));
 		if (!file.open(QIODevice::ReadOnly)) {
 			qWarning("%s: %s", qPrintable(file.fileName()),
 			  qPrintable(file.errorString()));
-			_data.insert(k, QByteArray());
+			_data.insert(k, new QByteArray());
 			return NAN;
 		} else {
-			it = _data.insert(k, file.readAll());
-			return height(c, *it);
+			ba = new QByteArray(file.readAll());
+			_data.insert(k, ba);
+			return height(c, ba);
 		}
 	} else
-		return height(c, *it);
+		return height(c, ba);
 }
diff --git a/src/data/dem.h b/src/data/dem.h
index a58f8ed4..2e4aa0e7 100644
--- a/src/data/dem.h
+++ b/src/data/dem.h
@@ -2,7 +2,7 @@
 #define DEM_H
 
 #include <QString>
-#include <QMap>
+#include <QCache>
 #include <QByteArray>
 
 class QString;
@@ -10,32 +10,38 @@ class Coordinates;
 
 class DEM
 {
-public:
-	static void setDir(const QString &path);
-	static qreal elevation(const Coordinates &c);
-
 private:
-	struct Key {
-		int lon;
-		int lat;
+	class Key {
+	public:
+		Key(int lon, int lat) : _lon(lon), _lat(lat) {}
 
-		Key(int lon, int lat) : lon(lon), lat(lat) {}
+		int lon() const {return _lon;}
+		int lat() const {return _lat;}
 
-		bool operator<(const Key &other) const
+		bool operator==(const Key &other) const
 		{
-			if (lon < other.lon)
-				return true;
-			else if (lon > other.lon)
-				return false;
-			else
-				return (lat < other.lat);
+			return (_lon == other._lon && _lat == other._lat);
 		}
+
+	private:
+		int _lon, _lat;
 	};
 
 	static QString fileName(const Key &key);
 
 	static QString _dir;
-	static QMap<Key, QByteArray> _data;
+	static QCache<Key, QByteArray> _data;
+
+public:
+	static void setDir(const QString &path);
+	static qreal elevation(const Coordinates &c);
+
+	friend uint qHash(const Key &key);
 };
 
+inline uint qHash(const DEM::Key &key)
+{
+	return (key.lon() ^ key.lat());
+}
+
 #endif // DEM_H