diff --git a/sbapp/sideband/sense.py b/sbapp/sideband/sense.py
index cd6cc1c..b64f36c 100644
--- a/sbapp/sideband/sense.py
+++ b/sbapp/sideband/sense.py
@@ -796,7 +796,7 @@ class Location(Sensor):
     obj_rh = None
     aamsl = None
     if self.data["altitude"] != None and self.data["latitude"] != None and self.data["longitude"] != None:
-      aamsl = self.get_aamsl()
+      aamsl = max(0, self.get_aamsl())
       coords = (self.data["latitude"], self.data["longitude"], aamsl)
       obj_ath = angle_to_horizon(coords)
       obj_rh = radio_horizon(aamsl)
@@ -825,7 +825,7 @@ class Location(Sensor):
         s = relative_to.sensors["location"]
         d = s.data
         if d != None and "latitude" in d and "longitude" in d and "altitude" in d:
-          lat = d["latitude"]; lon = d["longitude"]; alt = altitude_to_aamsl(d["altitude"], lat, lon)
+          lat = d["latitude"]; lon = d["longitude"]; alt = max(0, altitude_to_aamsl(d["altitude"], lat, lon))
           if lat != None and lon != None:
             if alt == None: alt = 0
             cs = (slat, slon, salt); cr = (lat, lon, alt)
diff --git a/sbapp/ui/telemetry.py b/sbapp/ui/telemetry.py
index 209edd8..cd79bdc 100644
--- a/sbapp/ui/telemetry.py
+++ b/sbapp/ui/telemetry.py
@@ -1275,7 +1275,7 @@ MDScreen:
                     MDTextField:
                         id: telemetry_s_fixed_altitude
                         size_hint: [0.382, None]
-                        hint_text: "Altitude"
+                        hint_text: "Ellipsoid Height (GPS Altitude)"
                         text: ""
                         font_size: dp(24)