diff --git a/src/map.c b/src/map.c
index 3db145ec96..cc749f604a 100644
--- a/src/map.c
+++ b/src/map.c
@@ -154,9 +154,10 @@ void map_update_tile_pointers()
 
 /**
  * Return the absolute height of an element, given its (x,y) coordinates
+ *
  *  ax: x
  *  cx: y
- *  dx: return
+ *  dx: return remember to & with 0xFFFF if you don't want water affecting results
  *  rct2: 0x00662783
  */
 int map_element_height(int x, int y)
diff --git a/src/viewport.c b/src/viewport.c
index d39bf92a8d..f1aa777363 100644
--- a/src/viewport.c
+++ b/src/viewport.c
@@ -281,7 +281,7 @@ void viewport_update_position(rct_window *window)
 	if (window->viewport_target_sprite != -1){
 		rct_sprite* sprite = &g_sprite_list[window->viewport_target_sprite];
 
-		int height = map_element_height(0xFFFF & sprite->unknown.x, 0xFFFF & sprite->unknown.y) - 16;
+		int height = map_element_height(0xFFFF & sprite->unknown.x, 0xFFFF & sprite->unknown.y) & 0xFFFF - 16;
 		int underground = sprite->unknown.z < height;
 
 		RCT2_CALLPROC_X(0x6E7A15, sprite->unknown.x, sprite->unknown.y, sprite->unknown.z, underground, (int)window, (int)viewport, 0);
diff --git a/src/window_peep.c b/src/window_peep.c
index ee168a8d80..e061b4ccf4 100644
--- a/src/window_peep.c
+++ b/src/window_peep.c
@@ -1179,7 +1179,7 @@ void window_peep_overview_tool_update(){
 }
 
 /* rct2: 0x664F72 */
-int sub_664F72(int x, int y, int edx){
+int sub_664F72(int x, int y, int z){
 	if (x > 0x1FFF || y > 0x1FFF){
 		RCT2_GLOBAL(RCT2_ADDRESS_GAME_COMMAND_ERROR_TEXT, uint16) = 0x6C1;
 		return 1;
@@ -1192,10 +1192,10 @@ int sub_664F72(int x, int y, int edx){
 		return 1;
 	}
 
-	edx >>= 3;
-	if ((edx & 0xFF) < map_element->base_height)return 0;
-	edx = (edx & 0xFF) - 2;
-	if (edx > map_element->base_height)return 0;
+	z >>= 3;
+	if ((z & 0xFF) < map_element->base_height)return 0;
+	z = (z & 0xFF) - 2;
+	if (z > map_element->base_height)return 0;
 
 	RCT2_GLOBAL(RCT2_ADDRESS_GAME_COMMAND_ERROR_TEXT, uint16) = 0x6C1;
 	return 1;
@@ -1211,25 +1211,32 @@ void window_peep_overview_tool_down(){
 
 	if (widgetIndex != WIDX_PICKUP) return;
 
-	int eax = x, ebx = y, ecx = 0, edx = widgetIndex, edi = 0, esi = (int)w, ebp = 0;
-	ebx += 16;
-	RCT2_CALLFUNC_X(0x689726, &eax, &ebx, &ecx, &edx, &esi, &edi, &ebp);
+	int dest_x = x, dest_y = y, ecx = 0, edx = widgetIndex, edi = 0, esi = (int)w, ebp = 0;
+	dest_y += 16;
+	RCT2_CALLFUNC_X(0x689726, &dest_x, &dest_y, &ecx, &edx, &esi, &edi, &ebp);
 
-	if (eax == 0x8000)return;
+	if (dest_x == 0x8000)return;
 
-	eax += 16;
-	ecx = ebx + 16;
-	edx = ((uint8*)edx)[2] * 8 + 16;
-	int _eax = eax & 0xFFE0, _ebx = ebx & 0xFFE0;
-	if (sub_664F72(eax & 0xFFE0, ebx & 0xFFE0, edx)){
+	// Set the coordinate of destination to be exactly 
+	// in the middle of a tile.
+	dest_x += 16;
+	dest_y += 16;
+	// Set the tile coordinate to top left of tile
+	int tile_y = dest_y & 0xFFE0;
+	int tile_x = dest_x & 0xFFE0;
+
+	int dest_z = ((uint8*)edx)[2] * 8 + 16;
+
+	if (sub_664F72(tile_x, tile_y, dest_z)){
 		window_error_open(0x785,-1);
 		return;
 	}
-	int _edx = edx>>3;
+
+	int _edx = dest_z >> 3;
 	_edx &= 0xFFFF00FF;
-	_edx |= edx << 8;
+	_edx |= dest_z << 8;
 	_edx += 0x100;
-	int flags = RCT2_CALLPROC_X(0x68B93A, eax & 0xFFE0, 0xF, ebx & 0xFFE0, _edx, (int)w, 0, 0);
+	int flags = RCT2_CALLPROC_X(0x68B93A, tile_x, 0xF, tile_y, _edx, (int)w, 0, 0);
 
 	if (flags & 0x100){
 		if (RCT2_GLOBAL(RCT2_ADDRESS_GAME_COMMAND_ERROR_TEXT, uint16) != 0x3A5 ){
@@ -1241,7 +1248,7 @@ void window_peep_overview_tool_down(){
 	}
 
 	rct_peep* peep = GET_PEEP(w->number);
-	RCT2_CALLPROC_X(0x0069E9D3, eax, 0, ebx, edx, (int)peep, 0, 0);
+	RCT2_CALLPROC_X(0x0069E9D3, dest_x, 0, dest_y, dest_z, (int)peep, 0, 0);
 	RCT2_CALLPROC_X(0x006EC473, 0, 0, 0, 0, (int)peep, 0, 0);
 	RCT2_CALLPROC_X(0x0069A409, 0, 0, 0, 0, (int)peep, 0, 0);
 	peep->state = 0;