diff --git a/conf/messages.xml b/conf/messages.xml
index 4a19a4de90..9bcbe6d2dc 100644
--- a/conf/messages.xml
+++ b/conf/messages.xml
@@ -37,12 +37,12 @@
 
    <message name="GPS" id="8">
      <field name="mode"       type="uint8"  unit="byte_mask"/>
-     <field name="utm_east"   type="int32"  unit="cm" alt_unit="m" alt_unit_coef="0.01"/>
-     <field name="utm_north"  type="int32"  unit="cm" alt_unit="m" alt_unit_coef="0.01"/>
-     <field name="course"     type="int16"  unit="decideg" alt_unit="deg" alt_unit_coef="0.1"/>
-     <field name="alt"        type="int32"  unit="mm" alt_unit="m" alt_unit_coef="0.001"/>
-     <field name="speed"      type="uint16" unit="cm/s" alt_unit="m/s" alt_unit_coef="0.01"/>
-     <field name="climb"      type="int16"  unit="cm/s" alt_unit="m/s" alt_unit_coef="0.01"/>
+     <field name="utm_east"   type="int32"  unit="cm" alt_unit="m"/>
+     <field name="utm_north"  type="int32"  unit="cm" alt_unit="m"/>
+     <field name="course"     type="int16"  unit="decideg" alt_unit="deg"/>
+     <field name="alt"        type="int32"  unit="mm" alt_unit="m"/>
+     <field name="speed"      type="uint16" unit="cm/s" alt_unit="m/s"/>
+     <field name="climb"      type="int16"  unit="cm/s" alt_unit="m/s"/>
      <field name="week"       type="uint16" unit="weeks"/>
      <field name="itow"       type="uint32" unit="ms"/>
      <field name="utm_zone"   type="uint8"/>
@@ -1104,18 +1104,18 @@
   </message>
 
   <message name="GPS_INT" id="155">
-    <field name="ecef_x"  type="int32" unit="cm"   alt_unit="m"   alt_unit_coef="0.01"/>
-    <field name="ecef_y"  type="int32" unit="cm"   alt_unit="m"   alt_unit_coef="0.01"/>
-    <field name="ecef_z"  type="int32" unit="cm"   alt_unit="m"   alt_unit_coef="0.01"/>
+    <field name="ecef_x"  type="int32" unit="cm"   alt_unit="m"/>
+    <field name="ecef_y"  type="int32" unit="cm"   alt_unit="m"/>
+    <field name="ecef_z"  type="int32" unit="cm"   alt_unit="m"/>
     <field name="lat"     type="int32" alt_unit="deg" alt_unit_coef="0.0000057296"/>
     <field name="lon"     type="int32" alt_unit="deg" alt_unit_coef="0.0000057296"/>
-    <field name="alt"     type="int32" unit="mm"   alt_unit="m"   alt_unit_coef="0.001"/>
-    <field name="hmsl"    type="int32" unit="mm"   alt_unit="m"   alt_unit_coef="0.001"/>
-    <field name="ecef_xd" type="int32" unit="cm/s" alt_unit="m/s" alt_unit_coef="0.01"/>
-    <field name="ecef_yd" type="int32" unit="cm/s" alt_unit="m/s" alt_unit_coef="0.01"/>
-    <field name="ecef_zd" type="int32" unit="cm/s" alt_unit="m/s" alt_unit_coef="0.01"/>
-    <field name="pacc"    type="int32" unit="cm"   alt_unit="m"   alt_unit_coef="0.01"/>
-    <field name="sacc"    type="int32" unit="cm/s" alt_unit="m/s" alt_unit_coef="0.01"/>
+    <field name="alt"     type="int32" unit="mm"   alt_unit="m"/>
+    <field name="hmsl"    type="int32" unit="mm"   alt_unit="m"/>
+    <field name="ecef_xd" type="int32" unit="cm/s" alt_unit="m/s"/>
+    <field name="ecef_yd" type="int32" unit="cm/s" alt_unit="m/s"/>
+    <field name="ecef_zd" type="int32" unit="cm/s" alt_unit="m/s"/>
+    <field name="pacc"    type="int32" unit="cm"   alt_unit="m"/>
+    <field name="sacc"    type="int32" unit="cm/s" alt_unit="m/s"/>
     <field name="tow"     type="uint32"/>
     <field name="pdop"    type="uint16"/>
     <field name="numsv"   type="uint8"/>
diff --git a/sw/lib/ocaml/pprz.ml b/sw/lib/ocaml/pprz.ml
index 774b7f1ea7..ba2c64c93a 100644
--- a/sw/lib/ocaml/pprz.ml
+++ b/sw/lib/ocaml/pprz.ml
@@ -168,6 +168,8 @@ let alt_unit_coef_of_xml = function xml ->
     | ("rad", "deg") | ("rad/s", "deg/s") -> string_of_float (180. /. pi)
     | ("m", "cm") | ("m/s", "cm/s") -> "100."
     | ("cm", "m") | ("cm/s", "m/s") -> "0.01"
+    | ("m", "mm") | ("m/s", "mm/s") -> "1000."
+    | ("mm", "m") | ("mm/s", "m/s") -> "0.001"
     | ("decideg", "deg") -> "0.1"
     | (_, _) -> "1."
 
diff --git a/sw/lib/ocaml/pprz.mli b/sw/lib/ocaml/pprz.mli
index 855dd2938c..b52124d3d5 100644
--- a/sw/lib/ocaml/pprz.mli
+++ b/sw/lib/ocaml/pprz.mli
@@ -93,8 +93,12 @@ val alt_unit_coef_of_xml : Xml.xml -> string
     rad -> deg
     m -> cm
     cm -> m
+    m -> mm
+    mm -> m
     m/s -> cm/s
     cm/s -> m/s
+    m/s -> mm/s
+    mm/s -> m/s
     decideg -> deg
     *)