AP_Terrain: use ahrs singleton

libraries/AP_Terrain/AP_Terrain.cpp

@@ -56,8 +56,7 @@ const AP_Param::GroupInfo AP_Terrain::var_info[] = {
 };
 
 // constructor
-AP_Terrain::AP_Terrain(AP_AHRS &_ahrs, const AP_Mission &_mission, const AP_Rally &_rally) :
-    ahrs(_ahrs),
+AP_Terrain::AP_Terrain(const AP_Mission &_mission, const AP_Rally &_rally) :
     mission(_mission),
     rally(_rally),
     disk_io_state(DiskIoIdle),
@@ -81,6 +80,8 @@ bool AP_Terrain::height_amsl(const Location &loc, float &height, bool corrected)
         return false;
     }
 
+    const AP_AHRS &ahrs = AP::ahrs();
+
     // quick access for home altitude
     if (loc.lat == home_loc.lat &&
         loc.lng == home_loc.lng) {
@@ -161,6 +162,8 @@ bool AP_Terrain::height_amsl(const Location &loc, float &height, bool corrected)
 */
 bool AP_Terrain::height_terrain_difference_home(float &terrain_difference, bool extrapolate)
 {
+    const AP_AHRS &ahrs = AP::ahrs();
+
     float height_home, height_loc;
     if (!height_amsl(ahrs.get_home(), height_home, false)) {
         // we don't know the height of home
@@ -208,7 +211,7 @@ bool AP_Terrain::height_above_terrain(float &terrain_altitude, bool extrapolate)
     }
 
     float relative_home_altitude;
-    ahrs.get_relative_position_D_home(relative_home_altitude);
+    AP::ahrs().get_relative_position_D_home(relative_home_altitude);
     relative_home_altitude = -relative_home_altitude;
 
     terrain_altitude = relative_home_altitude - terrain_difference;
@@ -254,7 +257,7 @@ float AP_Terrain::lookahead(float bearing, float distance, float climb_ratio)
     }
 
     Location loc;
-    if (!ahrs.get_position(loc)) {
+    if (!AP::ahrs().get_position(loc)) {
         // we don't know where we are
         return 0;
     }
@@ -295,6 +298,8 @@ void AP_Terrain::update(void)
     // just schedule any needed disk IO
     schedule_disk_io();
 
+    const AP_AHRS &ahrs = AP::ahrs();
+
     // try to ensure the home location is populated
     float height;
     height_amsl(ahrs.get_home(), height, false);
@@ -342,7 +347,7 @@ void AP_Terrain::log_terrain_data(DataFlash_Class &dataflash)
         return;
     }
     Location loc;
-    if (!ahrs.get_position(loc)) {
+    if (!AP::ahrs().get_position(loc)) {
         // we don't know where we are
         return;
     }

libraries/AP_Terrain/AP_Terrain.h

@@ -76,7 +76,7 @@
 
 class AP_Terrain {
 public:
-    AP_Terrain(AP_AHRS &_ahrs, const AP_Mission &_mission, const AP_Rally &_rally);
+    AP_Terrain(const AP_Mission &_mission, const AP_Rally &_rally);
 
     /* Do not allow copies */
     AP_Terrain(const AP_Terrain &other) = delete;
@@ -336,10 +336,6 @@ private:
     AP_Int8  enable;
     AP_Int16 grid_spacing; // meters between grid points
 
-    // reference to AHRS, so we can ask for our position,
-    // heading and speed
-    AP_AHRS &ahrs;
-
     // reference to AP_Mission, so we can ask preload terrain data for 
     // all waypoints
     const AP_Mission &mission;

libraries/AP_Terrain/TerrainGCS.cpp

@@ -92,7 +92,7 @@ void AP_Terrain::send_request(mavlink_channel_t chan)
     schedule_disk_io();
 
     Location loc;
-    if (!ahrs.get_position(loc)) {
+    if (!AP::ahrs().get_position(loc)) {
         // we don't know where we are
         return;
     }
@@ -206,6 +206,7 @@ void AP_Terrain::send_terrain_report(mavlink_channel_t chan, const Location &loc
     float home_terrain_height = 0;
     uint16_t spacing = 0;
     Location current_loc;
+    const AP_AHRS &ahrs = AP::ahrs();
     if (ahrs.get_position(current_loc) &&
         height_amsl(ahrs.get_home(), home_terrain_height, false) &&
         height_amsl(loc, terrain_height, false)) {