diff --git a/sw/ground_segment/cockpit/map2d.ml b/sw/ground_segment/cockpit/map2d.ml
index 139f42ff99..1c64c4e6dc 100644
--- a/sw/ground_segment/cockpit/map2d.ml
+++ b/sw/ground_segment/cockpit/map2d.ml
@@ -3,7 +3,7 @@
  *
  * Multi aircrafts map display
  *  
- * Copyright (C) 2004 CENA/ENAC, Pascal Brisset, Antoine Drouin
+ * Copyright (C) 2004-2006 ENAC, Pascal Brisset, Antoine Drouin
  *
  * This file is part of paparazzi.
  *
@@ -52,6 +52,12 @@ let (//) = Filename.concat
 let default_path_srtm = home // "data" // "srtm"
 let default_path_maps = home // "data" // "maps" // ""
 let default_path_missions = home // "conf"
+let gm_tiles_path = home // "var" // "maps"
+let _ = 
+  ignore (Sys.command (sprintf "mkdir -p %s" gm_tiles_path))
+
+let google_maps_url = fun s -> sprintf "http://kh1.google.com/kh?n=404&v=3&t=%s" s
+
 
 
 type aircraft = {
@@ -117,17 +123,23 @@ let set_geo_ref = fun geomap wgs84 ->
   map_ref := Some utm_ref
 
 
+exception Wget_failure of string
 
-let file_of_url = fun ?(extension=".xml") url ->
+let file_of_url = fun ?(extension=".xml") ?dest url ->
   if String.sub url 0 7 = "file://" then
     String.sub url 7 (String.length url - 7)
   else
-    let tmp_file = Filename.temp_file "fp" extension in
+    let tmp_file =
+      match dest with 
+	Some s -> s
+      | None -> Filename.temp_file "fp" extension in
     let c = sprintf "wget --cache=off -O %s '%s'" tmp_file url in
     if Sys.command c = 0 then
       tmp_file
-    else
-      failwith c
+    else begin
+      Sys.remove tmp_file;
+      raise (Wget_failure url)
+    end
 
 let load_mission = fun color geomap xml ->
   let lat0 = float_attr xml "lat0"
@@ -487,19 +499,40 @@ let en_of_wgs84 = fun geomap wgs84 ->
   {G.east=utm.utm_x -. utm_ref.utm_x; north=utm.utm_y -. utm_ref.utm_y}
 
 
+let is_prefix = fun a b ->
+  String.length b >= String.length a &&
+  a = String.sub b 0 (String.length a)
+
+let get_gm_from_cache = fun f ->
+  let files = Sys.readdir gm_tiles_path in
+  let rec loop = fun i ->
+    if i < Array.length files then
+      let fi = files.(i) in
+      if is_prefix (Filename.chop_extension fi) f then
+	let (sw, s) = Latlong.gm_lat_long_of_tile f in
+	(gm_tiles_path // fi, sw, s)
+      else
+	loop (i+1)
+    else
+      raise Not_found in
+  loop 0
+
 
 let rec get_gm_tile = fun wgs84 zoom ->
   if zoom < 10 then
     try
       let (gm_string, sw, scale) = Latlong.gm_tile_string wgs84 zoom in
-      let url = sprintf "http://kh1.google.com/kh?n=404&v=3&t=%s" gm_string in
-      let jpg_file = file_of_url ~extension:".jpg" url in
-
-      (jpg_file, sw, scale)
+      try get_gm_from_cache gm_string with
+	Not_found ->
+	  let url = google_maps_url gm_string in
+	  let jpg_file = gm_tiles_path // (gm_string ^ ".jpg") in
+	  ignore (file_of_url ~extension:".jpg" ~dest:jpg_file url);
+	  (jpg_file, sw, scale)
     with (** Error, let's try a lower zoom *)
-      _ -> get_gm_tile wgs84 (zoom+1)
+      Wget_failure __ -> get_gm_tile wgs84 (zoom+1)
   else
-    failwith "get_gm_tile"
+    failwith "download_gm_tile"
+
 
 
 
diff --git a/sw/lib/ocaml/latlong.ml b/sw/lib/ocaml/latlong.ml
index 1119dd27e4..091192202c 100644
--- a/sw/lib/ocaml/latlong.ml
+++ b/sw/lib/ocaml/latlong.ml
@@ -3,7 +3,7 @@
  *
  * Geographic conversion utilities
  *  
- * Copyright (C) 2004 CENA/ENAC, Pascal Brisset, Antoine Drouin
+ * Copyright (C) 2004-2006 ENAC, Pascal Brisset, Antoine Drouin
  *
  * This file is part of paparazzi.
  *
@@ -360,6 +360,22 @@ let (/.=) r x = r := !r /. x
 let (+.=) r x = r := !r +. x
 let (-.=) r x = r := !r -. x
 
+
+let gm_pos_and_scale = fun keyholeString tLat latHeight tLon lonWidth ->
+  let tmp_lat = fun l -> 2. *. atan (exp (l *. pi)) -. pi/.2. in
+  let bl_lat = tmp_lat tLat in
+  let tr_lat = tmp_lat (tLat +. latHeight) in
+  let bottom_left = {posn_lat = bl_lat ; posn_long = tLon *. pi} in
+  let top_right = {posn_lat = tr_lat;
+		   posn_long = bottom_left.posn_long +. lonWidth *. pi } in
+
+  let utm_bottom_left = utm_of WGS84 bottom_left
+  and utm_top_right = utm_of WGS84 top_right in
+(***   Printf.fprintf stderr "%fx%f\n" (utm_bottom_left.utm_x -. utm_top_right.utm_x) (utm_bottom_left.utm_y -. utm_top_right.utm_y); ***)
+  let scale = utm_distance utm_bottom_left utm_top_right  /. sqrt (2. *. 256.*.256.) in
+  (keyholeString, bottom_left, scale)
+
+
 (** Returns a keyhole string for a longitude (x), latitude (y), and zoom 
    for Google Maps (http://www.ponies.me.uk/maps/GoogleTileUtils.java) *)
 let gm_tile_string = fun wgs84 zoom ->
@@ -403,26 +419,14 @@ let gm_tile_string = fun wgs84 zoom ->
       end
     end
   done;
-  let tmp_lat = fun l -> 2. *. atan (exp (l *. pi)) -. pi/.2. in
-  let bl_lat = tmp_lat !tLat in
-  let tr_lat = tmp_lat (!tLat +. !latHeight) in
-  let bottom_left = {posn_lat = bl_lat ; posn_long = !tLon *. pi} in
-  let top_right = {posn_lat = tr_lat;
-		   posn_long = bottom_left.posn_long +. !lonWidth *. pi } in
-
-  let utm_bottom_left = utm_of WGS84 bottom_left
-  and utm_top_right = utm_of WGS84 top_right in
-  Printf.fprintf stderr "%fx%f\n" (utm_bottom_left.utm_x -. utm_top_right.utm_x) (utm_bottom_left.utm_y -. utm_top_right.utm_y);
-  let scale = utm_distance utm_bottom_left utm_top_right  /. sqrt (2. *. 256.*.256.) in
-  (Buffer.contents keyholeString, bottom_left, scale)
-
+  gm_pos_and_scale (Buffer.contents keyholeString) !tLat !latHeight !tLon !lonWidth
 
 let gm_lat_long_of_tile = fun keyholeStr ->
   assert(keyholeStr.[0] = 't');
   
   let lon  = ref (-180.)
   and lonWidth = ref 360. 
-  and  lat       = ref (-1.) 
+  and lat       = ref (-1.) 
   and latHeight = ref 2. in
   
   for i = 1 to String.length keyholeStr - 1  do
@@ -439,11 +443,5 @@ let gm_lat_long_of_tile = fun keyholeStr ->
     | _ -> invalid_arg ("gm_get_lat_long " ^ keyholeStr)
   done;
 
-  latHeight +.= !lat;
-  latHeight := (2. *. atan (exp (pi *. !latHeight))) -. (pi /. 2.);
-
-  lat := (2. *. atan (exp (pi *. !lat))) -. (pi /. 2.);
-
-  latHeight -.= !lat;
-  lon := (Deg>>Rad)!lon;
-  { posn_lat = !lat; posn_long = !lon }
+  let (_, sw, s) = gm_pos_and_scale keyholeStr !lat !latHeight (!lon/.180.) (!lonWidth/.180.) in
+  (sw, s)
diff --git a/sw/lib/ocaml/latlong.mli b/sw/lib/ocaml/latlong.mli
index daccf2e17f..dd7c8e92c7 100644
--- a/sw/lib/ocaml/latlong.mli
+++ b/sw/lib/ocaml/latlong.mli
@@ -117,8 +117,8 @@ val of_string : string -> geographic
 
 val gm_tile_string : geographic -> int -> string * geographic * float
 (** [gm_tile_string geo zoom] Returns the string code designing the
-   Google Map tile *)
+   Google Map tile, coordinates of SW corner and scale *)
 
-val gm_lat_long_of_tile : string -> geographic
+val gm_lat_long_of_tile : string -> geographic * float
 (** [gm_lat_long_of_tile google_maps_tile_key] Returns the coordinates of the
-South West corner of the given tile. *)
+South West corner and the scale of the given tile. *)