diff --git a/sw/ground_segment/cockpit/gcs.glade b/sw/ground_segment/cockpit/gcs.glade
index 7f00cf86ed..1bc9bebfe5 100644
--- a/sw/ground_segment/cockpit/gcs.glade
+++ b/sw/ground_segment/cockpit/gcs.glade
@@ -171,7 +171,7 @@
                                         <child>
                                           <widget class="GtkEventBox" id="eventbox14">
                                             <property name="visible">True</property>
-                                            <property name="tooltip" translatable="yes">Above Ground Level (m), climb indicator, vertical speed (m/s)</property>
+                                            <property name="tooltip" translatable="yes">Above Ground Level from SRTM if available, ground reference otherwise (m), climb indicator, vertical speed (m/s)</property>
                                             <child>
                                               <widget class="GtkDrawingArea" id="drawingarea_agl">
                                                 <property name="visible">True</property>
diff --git a/sw/lib/ocaml/mapCanvas.ml b/sw/lib/ocaml/mapCanvas.ml
index 5e380f07e2..9077564795 100644
--- a/sw/lib/ocaml/mapCanvas.ml
+++ b/sw/lib/ocaml/mapCanvas.ml
@@ -645,7 +645,7 @@ object (self)
 
 
 class widget =  fun ?(height=800) ?(srtm=false) ?width ?projection ?georef () ->
-  let srtm = GMenu.check_menu_item ~label:"SRTM" ~active:srtm () in
+  let srtm = GMenu.check_menu_item ~label:"display SRTM alt" ~active:srtm () in
   let lbl_xy = GMisc.label ()
   and lbl_geo = GMisc.label ()
   and lbl_alt =  GMisc.label ()
@@ -676,6 +676,7 @@ class widget =  fun ?(height=800) ?(srtm=false) ?width ?projection ?georef () ->
       let bg_menu = my_check_menu_item "Background" ~active:true ~callback:self#switch_background ~packing:self#file_menu#append () in
 
       let tooltips = GData.tooltips () in
+      tooltips#set_tip srtm#coerce ~text:"Display SRTM alt at pointer position (will request for download if not available)";
 
       let b = GButton.button ~packing:toolbar#add () in
       ignore (b#connect#clicked (fun _ -> bg_menu#activate ()));
@@ -777,7 +778,9 @@ class widget =  fun ?(height=800) ?(srtm=false) ?width ?projection ?georef () ->
 
     method display_alt = fun wgs84 ->
       if srtm#active then
-    lbl_alt#set_text (sprintf " SRTM:%dm"(self#altitude wgs84))
+        lbl_alt#set_text (sprintf "  SRTM:%dm"(self#altitude wgs84))
+      else if not (Srtm.available wgs84) then
+        lbl_alt#set_text (sprintf "  SRTM: N/A")
 
     method display_group = fun s ->  lbl_group#set_text s
 
diff --git a/sw/lib/ocaml/srtm.ml b/sw/lib/ocaml/srtm.ml
index 672744f070..22d3b7a1ae 100644
--- a/sw/lib/ocaml/srtm.ml
+++ b/sw/lib/ocaml/srtm.ml
@@ -79,6 +79,9 @@ let of_wgs84 = fun geo ->
 let of_utm = fun utm ->
   of_wgs84 (Latlong.of_utm WGS84 utm)
 
+let available = fun geo ->
+  try ignore(of_wgs84 geo); true with _ -> false
+
 let area_of_tile = fun tile ->
   let area = open_compressed "srtm.data.bz2" in
   let rec _area_of_tile = fun () ->
diff --git a/sw/lib/ocaml/srtm.mli b/sw/lib/ocaml/srtm.mli
index c3742b41bf..8c0a9becc7 100644
--- a/sw/lib/ocaml/srtm.mli
+++ b/sw/lib/ocaml/srtm.mli
@@ -33,11 +33,14 @@ exception Tile_not_found of error
 
 val error : error -> string
 
+val available : Latlong.geographic -> bool
+(** [available wgs84_pos] Returns true if srtm tile is available *)
+
 val of_utm : Latlong.utm -> int
 (** [of_utm utm_pos] Returns the altitude of the given UTM position *)
 
 val of_wgs84 : Latlong.geographic -> int
-(** [of_utm utm_pos] Returns the altitude of the given geographic position *)
+(** [of_wgs84 wgs84_pos] Returns the altitude of the given geographic position *)
 
 val area_of_tile : string -> string