Index: src/smallmap_gui.cpp
===================================================================
--- src/smallmap_gui.cpp	(Revision 20857)
+++ src/smallmap_gui.cpp	(Arbeitskopie)
@@ -838,6 +838,24 @@
 		}
 	}
 
+	Point GetSmallMapCoordIncludingHeight(Point viewportCoord) const
+	{
+		/* First find out which tile would be there if we ignore height */
+		Point pt = InverseRemapCoords(viewportCoord.x, viewportCoord.y);
+		Point ptWithoutHeight = {pt.x / TILE_SIZE, pt.y / TILE_SIZE};
+
+		/* Problem: There are mountains.  So the tile actually displayed at the given position
+		 * might be the high mountain of 30 tiles south.
+		 * Unfortunately, there is no closed formula for finding such a tile.
+		 * We call GetRowAtTile originally implemented for the viewport code, which performs
+		 * a interval search.  For details, see its documentation. */
+		int rowWithoutHeight = ptWithoutHeight.x + ptWithoutHeight.y;
+		int rowWithHeight = GetRowAtTile(viewportCoord.y, ptWithoutHeight);
+		int rowOffset = rowWithHeight - rowWithoutHeight;
+		Point ptWithHeight = {ptWithoutHeight.x + rowOffset / 2, ptWithoutHeight.y + rowOffset / 2};
+		return ptWithHeight;
+	}
+
 	/**
 	 * Draws vertical part of map indicator
 	 * @param x X coord of left/right border of main viewport
@@ -870,19 +888,23 @@
 		/* Find main viewport. */
 		const ViewPort *vp = FindWindowById(WC_MAIN_WINDOW, 0)->viewport;
 
-		Point tile = InverseRemapCoords(vp->virtual_left, vp->virtual_top);
-		Point tl = this->RemapTile(tile.x >> 4, tile.y >> 4);
-		tl.x -= this->subscroll;
+		Point upperLeftViewportCoord = {vp->virtual_left, vp->virtual_top};
+		Point upperLeftSmallMapCoord = GetSmallMapCoordIncludingHeight(upperLeftViewportCoord);
+		Point upperLeft = this->RemapTile(upperLeftSmallMapCoord.x, upperLeftSmallMapCoord.y);
+		/* why do we do this? in my tests subscroll was zero */
+		upperLeft.x -= this->subscroll;
 
-		tile = InverseRemapCoords(vp->virtual_left + vp->virtual_width, vp->virtual_top + vp->virtual_height);
-		Point br = this->RemapTile(tile.x >> 4, tile.y >> 4);
-		br.x -= this->subscroll;
+		Point lowerRightViewportCoord = {vp->virtual_left + vp->virtual_width, vp->virtual_top + vp->virtual_height};
+		Point lowerRightSmallMapCoord = GetSmallMapCoordIncludingHeight(lowerRightViewportCoord);
+		Point lowerRight = this->RemapTile(lowerRightSmallMapCoord.x, lowerRightSmallMapCoord.y);
+		/* why do we do this? in my tests subscroll was zero */
+		lowerRight.x -= this->subscroll;
 
-		SmallMapWindow::DrawVertMapIndicator(tl.x, tl.y, br.y);
-		SmallMapWindow::DrawVertMapIndicator(br.x, tl.y, br.y);
+		SmallMapWindow::DrawVertMapIndicator(upperLeft.x, upperLeft.y, lowerRight.y);
+		SmallMapWindow::DrawVertMapIndicator(lowerRight.x, upperLeft.y, lowerRight.y);
 
-		SmallMapWindow::DrawHorizMapIndicator(tl.x, br.x, tl.y);
-		SmallMapWindow::DrawHorizMapIndicator(tl.x, br.x, br.y);
+		SmallMapWindow::DrawHorizMapIndicator(upperLeft.x, lowerRight.x, upperLeft.y);
+		SmallMapWindow::DrawHorizMapIndicator(upperLeft.x, lowerRight.x, lowerRight.y);
 	}
 
 	/**
@@ -1175,6 +1197,18 @@
 				pt = RemapCoords(this->scroll_x + pt.x * TILE_SIZE + this->zoom * (TILE_SIZE - sub * TILE_SIZE / 4),
 						this->scroll_y + pt.y * TILE_SIZE + sub * this->zoom * TILE_SIZE / 4, 0);
 
+				/* correct y coordinate according to the height level at the chosen tile
+				 * - so far we assumed height zero.  Calculations here according to
+				 * TranslateXYToTileCoord in viewport.cpp */
+				Point ptScaled = {pt.x / (int)(4 * TILE_SIZE), pt.y / (int)(2 * TILE_SIZE)};
+				Point tileCoord = {ptScaled.y - ptScaled.x, ptScaled.y + ptScaled.x};
+
+				if (tileCoord.x >= 0 && tileCoord.y >= 0
+				 && tileCoord.x < (int)MapMaxX() && tileCoord.y < (int)MapMaxY()) {
+					int clicked_tile_height = TileHeight(TileXY(tileCoord.x, tileCoord.y));
+					pt.y -= clicked_tile_height * TILE_HEIGHT;
+				}
+
 				w->viewport->follow_vehicle = INVALID_VEHICLE;
 				w->viewport->dest_scrollpos_x = pt.x - (w->viewport->virtual_width  >> 1);
 				w->viewport->dest_scrollpos_y = pt.y - (w->viewport->virtual_height >> 1);
@@ -1373,12 +1407,19 @@
 
 	void SmallMapCenterOnCurrentPos()
 	{
+		/* Goal: Given the viewport coordinates of the middle of the map window, find
+		 * out which tile is displayed there. */
+
+		/* First find out which tile would be there if we ignore height */
 		const ViewPort *vp = FindWindowById(WC_MAIN_WINDOW, 0)->viewport;
-		Point pt = InverseRemapCoords(vp->virtual_left + vp->virtual_width  / 2, vp->virtual_top  + vp->virtual_height / 2);
+		Point viewportCenter = {vp->virtual_left + vp->virtual_width  / 2, vp->virtual_top  + vp->virtual_height / 2};
+		Point ptWithHeight = GetSmallMapCoordIncludingHeight(viewportCenter);
 
+		/* And finally scroll to that position. */
 		int sub;
 		const NWidgetBase *wid = this->GetWidget<NWidgetBase>(SM_WIDGET_MAP);
-		Point sxy = this->ComputeScroll(pt.x / TILE_SIZE, pt.y / TILE_SIZE, max(0, (int)wid->current_x / 2 - 2), wid->current_y / 2, &sub);
+		Point sxy = this->ComputeScroll(ptWithHeight.x, ptWithHeight.y,
+				max(0, (int)wid->current_x / 2 - 2), wid->current_y / 2, &sub);
 		this->SetNewScroll(sxy.x, sxy.y, sub);
 		this->SetDirty();
 	}