Clean up GPS code and add some flags per #1740

src/gps/NMEAGPS.cpp

@@ -223,13 +223,10 @@ bool NMEAGPS::lookForLocation()
         }
     }
 
-/*
-    // REDUNDANT?
-    // expect gps pos lat=37.520825, lon=-122.309162, alt=158
-    DEBUG_MSG("new NMEA GPS pos lat=%f, lon=%f, alt=%d, dop=%g, heading=%f\n",
-              latitude * 1e-7, longitude * 1e-7, altitude, dop * 1e-2,
-              heading * 1e-5);
-*/
+    if (reader.speed.isUpdated() && reader.speed.isValid()) {
+        p.ground_speed = reader.speed.kmph() * 1e3; // Scale the speed (in km/h * 10^-2) to match the expected m/s * 10^-5
+    }
+
     return true;
 }