GPS: fixes after review

Ensure 3D fix before returning velocity_down
UBLOX: restore check of fix_status as part of determining 2D or 3D fix
SIRF: add missing brackets on fix type check

libraries/AP_GPS/AP_GPS_SIRF.cpp

@@ -174,7 +174,7 @@ AP_GPS_SIRF::_parse_gps(void)
         // parse fix type
         if (_buffer.nav.fix_invalid) {
             fix = GPS::FIX_NONE;
-        }else if (_buffer.nav.fix_type & FIX_MASK == FIX_3D) {
+        }else if ((_buffer.nav.fix_type & FIX_MASK) == FIX_3D) {
             fix = GPS::FIX_3D;
         }else{
             fix = GPS::FIX_2D;

libraries/AP_GPS/AP_GPS_UBLOX.cpp

@@ -228,10 +228,15 @@ AP_GPS_UBLOX::_parse_gps(void)
         Debug("MSG_STATUS fix_status=%u fix_type=%u",
               _buffer.status.fix_status,
               _buffer.status.fix_type);
-        if (_buffer.status.fix_type == AP_GPS_UBLOX::FIX_3D) {
-            next_fix = GPS::FIX_3D;
-        }else if (_buffer.status.fix_type == AP_GPS_UBLOX::FIX_2D) {
-            next_fix = GPS::FIX_2D;
+        if (_buffer.status.fix_status & NAV_STATUS_FIX_VALID) {
+            if( _buffer.status.fix_type == AP_GPS_UBLOX::FIX_3D) {
+                next_fix = GPS::FIX_3D;
+            }else if (_buffer.status.fix_type == AP_GPS_UBLOX::FIX_2D) {
+                next_fix = GPS::FIX_2D;
+            }else{
+                next_fix = GPS::FIX_NONE;
+                fix = GPS::FIX_NONE;
+            }
         }else{
             next_fix = GPS::FIX_NONE;
             fix = GPS::FIX_NONE;
@@ -241,10 +246,15 @@ AP_GPS_UBLOX::_parse_gps(void)
         Debug("MSG_SOL fix_status=%u fix_type=%u",
               _buffer.solution.fix_status,
               _buffer.solution.fix_type);
-        if (_buffer.status.fix_type == AP_GPS_UBLOX::FIX_3D) {
-            next_fix = GPS::FIX_3D;
-        }else if (_buffer.status.fix_type == AP_GPS_UBLOX::FIX_2D) {
-            next_fix = GPS::FIX_2D;
+        if (_buffer.status.fix_status & NAV_STATUS_FIX_VALID) {
+            if( _buffer.status.fix_type == AP_GPS_UBLOX::FIX_3D) {
+                next_fix = GPS::FIX_3D;
+            }else if (_buffer.status.fix_type == AP_GPS_UBLOX::FIX_2D) {
+                next_fix = GPS::FIX_2D;
+            }else{
+                next_fix = GPS::FIX_NONE;
+                fix = GPS::FIX_NONE;
+            }
         }else{
             next_fix = GPS::FIX_NONE;
             fix = GPS::FIX_NONE;

libraries/AP_GPS/GPS.h

@@ -141,7 +141,7 @@ public:
         return _status >= GPS_OK_FIX_2D ? _velocity_east  : 0;
     }
     float velocity_down(void)  {
-        return _status >= GPS_OK_FIX_2D ? _velocity_down  : 0;
+        return _status >= GPS_OK_FIX_3D ? _velocity_down  : 0;
     }
 
     // last ground speed in m/s. This can be used when we have no GPS