diff --git a/src/tile.cpp b/src/tile.cpp
new file mode 100644
--- /dev/null
+++ b/src/tile.cpp
@@ -0,0 +1,63 @@
+/* $Id$ */
+
+#include "stdafx.h"
+#include "tile.h"
+
+Slope GetTileSlope(TileIndex tile, uint *h)
+{
+	uint a;
+	uint b;
+	uint c;
+	uint d;
+	uint min;
+	uint r;
+
+	assert(tile < MapSize());
+
+	if (TileX(tile) == MapMaxX() || TileY(tile) == MapMaxY()) {
+		if (h != NULL) *h = 0;
+		return 0;
+	}
+
+	min = a = TileHeight(tile);
+	b = TileHeight(tile + TileDiffXY(1, 0));
+	if (min >= b) min = b;
+	c = TileHeight(tile + TileDiffXY(0, 1));
+	if (min >= c) min = c;
+	d = TileHeight(tile + TileDiffXY(1, 1));
+	if (min >= d) min = d;
+
+	r = SLOPE_FLAT;
+	if ((a -= min) != 0) r += (--a << 4) + SLOPE_N;
+	if ((c -= min) != 0) r += (--c << 4) + SLOPE_E;
+	if ((d -= min) != 0) r += (--d << 4) + SLOPE_S;
+	if ((b -= min) != 0) r += (--b << 4) + SLOPE_W;
+
+	if (h != NULL) *h = min * TILE_HEIGHT;
+
+	return r;
+}
+
+uint GetTileZ(TileIndex tile)
+{
+	uint h;
+	GetTileSlope(tile, &h);
+	return h;
+}
+
+
+uint GetTileMaxZ(TileIndex t)
+{
+	uint max;
+	uint h;
+
+	h = TileHeight(t);
+	max = h;
+	h = TileHeight(t + TileDiffXY(1, 0));
+	if (h > max) max = h;
+	h = TileHeight(t + TileDiffXY(0, 1));
+	if (h > max) max = h;
+	h = TileHeight(t + TileDiffXY(1, 1));
+	if (h > max) max = h;
+	return max * 8;
+}