diff --git a/src/Aerolab.cpp b/src/Aerolab.cpp
index 2aa5031f7..be2c8e511 100644
--- a/src/Aerolab.cpp
+++ b/src/Aerolab.cpp
@@ -334,7 +334,7 @@ Aerolab::setData(RideItem *_rideItem, bool new_zoom) {
       int npoints = ride->dataPoints().size();
       double dt = ride->recIntSecs();
       veArray.resize(dataPresent->watts ? npoints : 0);
-      altArray.resize(dataPresent->alt ? npoints : 0);
+      altArray.resize(dataPresent->alt || constantAlt ? npoints : 0);
       timeArray.resize(dataPresent->watts ? npoints : 0);
       distanceArray.resize(dataPresent->watts ? npoints : 0);
 
@@ -355,7 +355,7 @@ Aerolab::setData(RideItem *_rideItem, bool new_zoom) {
       if (!altArray.empty()) {
         have_recorded_alt_curve = true;
         altCurve->attach(this);
-        altCurve->setVisible(dataPresent->alt);
+        altCurve->setVisible(dataPresent->alt || constantAlt );
       }
 
       // Fill the virtual elevation profile with data from the ride data:
@@ -368,10 +368,19 @@ Aerolab::setData(RideItem *_rideItem, bool new_zoom) {
         e = eoffset;
 
       timeArray[arrayLength]  = p1->secs / 60.0;
-      if ( have_recorded_alt_curve )
-        altArray[arrayLength] = (useMetricUnits
+      if ( have_recorded_alt_curve ) {
+          if ( constantAlt && arrayLength > 0) {
+              altArray[arrayLength] = altArray[arrayLength-1];
+          }
+          else  {
+              if ( constantAlt && !dataPresent->alt)
+                  altArray[arrayLength] = 0;
+              else
+                altArray[arrayLength] = (useMetricUnits
                    ? p1->alt
                    : p1->alt * FEET_PER_METER);
+          }
+      }
 
       // Unpack:
       double power = max(0, p1->watts);
@@ -605,6 +614,12 @@ Aerolab::setAutoEoffset(int value)
     adjustEoffset();
 }
 
+void
+Aerolab::setConstantAlt(int value)
+{
+    constantAlt = value;
+}
+
 void
 Aerolab::setByDistance(int value) {
   bydist = value;
@@ -788,7 +803,7 @@ QString Aerolab::estimateCdACrr(RideItem *rideItem)
 
     if(ride) {
         const RideFileDataPresent *dataPresent = ride->areDataPresent();
-        if(dataPresent->alt && dataPresent->watts) {
+        if(( dataPresent->alt || constantAlt )  && dataPresent->watts) {
             double dt = ride->recIntSecs();
             int npoints = ride->dataPoints().size();
             double X1[npoints], X2[npoints], Egain[npoints];
diff --git a/src/Aerolab.h b/src/Aerolab.h
index 253914eaf..ec0dfdd53 100644
--- a/src/Aerolab.h
+++ b/src/Aerolab.h
@@ -65,6 +65,7 @@ class Aerolab : public QwtPlot {
   public slots:
 
   void setAutoEoffset(int value);
+  void setConstantAlt(int value);
   void setByDistance(int value);
   void configChanged();
 
@@ -102,6 +103,7 @@ class Aerolab : public QwtPlot {
   int smooth;
   bool bydist;
   bool autoEoffset;
+  bool constantAlt;
   int arrayLength;
   int iCrr;
   int iCda;
diff --git a/src/AerolabWindow.cpp b/src/AerolabWindow.cpp
index d3b14d85a..871e98b44 100644
--- a/src/AerolabWindow.cpp
+++ b/src/AerolabWindow.cpp
@@ -112,6 +112,7 @@ AerolabWindow::AerolabWindow(MainWindow *mainWindow) :
   //etaLayout->addWidget( etaQLCDNumber );
   etaLayout->addWidget( etaSlider );
 
+
   // Add to leftControls:
   leftControls->addLayout( crrLayout );
   leftControls->addLayout( cdaLayout );
@@ -190,9 +191,16 @@ AerolabWindow::AerolabWindow(MainWindow *mainWindow) :
   //eoffsetLayout->addWidget( eoffsetQLCDNumber );
   eoffsetLayout->addWidget( eoffsetSlider );
 
+  QVBoxLayout *checkboxLayout = new QVBoxLayout;
   QCheckBox *eoffsetAuto = new QCheckBox(tr("eoffset auto"), this);
   eoffsetAuto->setCheckState(Qt::Checked);
-  eoffsetLayout->addWidget(eoffsetAuto);
+  checkboxLayout->addWidget(eoffsetAuto);
+
+  QCheckBox *constantAlt = new QCheckBox(tr("Constant altitude (velodrome,...)"), this);
+  checkboxLayout->addWidget(constantAlt);
+
+  eoffsetLayout->addLayout(checkboxLayout);
+
 
   QHBoxLayout *smoothLayout = new QHBoxLayout;
   QComboBox *comboDistance = new QComboBox();
@@ -239,6 +247,7 @@ AerolabWindow::AerolabWindow(MainWindow *mainWindow) :
   connect(eoffsetSlider, SIGNAL(valueChanged(int)), this, SLOT(setEoffsetFromSlider()));
   connect(eoffsetLineEdit, SIGNAL(textChanged(const QString)), this, SLOT(setEoffsetFromText(const QString)));
   connect(eoffsetAuto, SIGNAL(stateChanged(int)), this, SLOT(setAutoEoffset(int)));
+  connect(constantAlt, SIGNAL(stateChanged(int)), this, SLOT(setConstantAlt(int)));
   connect(comboDistance, SIGNAL(currentIndexChanged(int)), this, SLOT(setByDistance(int)));
   connect(btnEstCdACrr, SIGNAL(clicked()), this, SLOT(doEstCdACrr()));
   connect(mainWindow, SIGNAL(configChanged()), aerolab, SLOT(configChanged()));
@@ -462,6 +471,15 @@ AerolabWindow::setAutoEoffset(int value)
     aerolab->setAutoEoffset(value);
 }
 
+void
+AerolabWindow::setConstantAlt(int value)
+{
+    aerolab->setConstantAlt(value);
+    // refresh
+    RideItem *ride = myRideItem;
+    aerolab->setData(ride, false);
+}
+
 void
 AerolabWindow::setByDistance(int value)
 {
diff --git a/src/AerolabWindow.h b/src/AerolabWindow.h
index f8b496021..0fc52cc81 100644
--- a/src/AerolabWindow.h
+++ b/src/AerolabWindow.h
@@ -61,6 +61,7 @@ class AerolabWindow : public GcWindow {
   void setEoffsetFromText(const QString text);
   void doEstCdACrr();
   void setAutoEoffset(int value);
+  void setConstantAlt(int value);
   void setByDistance(int value);
   void rideSelected();
   void zoomChanged();