AP_Radar: Rearrange OSD text items and add relative heading arrow

Moves peer distance with direction to arrow to second line.
Adds relative heading arrow (peer heading relative to current craft) to first line.
Moves vertical distance to first line.

First line elements: Relative heading/Peer ID/Vertical direction/Vertical distance
Second line elements: Direction to peer arrow/horizontal distance to peer

libraries/AP_OSD/AP_OSD_Screen.cpp

@@ -1706,26 +1706,31 @@ void AP_OSD_Screen::draw_radar(uint8_t x, uint8_t y)
     Location loc;
     if (ahrs.get_location(loc) && ap_radar->get_peer_healthy(id)) {
         const Location &peer_loc = ap_radar->get_peer(id).location;
+        uint16_t peer_heading = ap_radar->get_peer(id).heading;
         float distance = loc.get_distance(peer_loc);
         ftype vertical_distance;
         if (!peer_loc.get_alt_distance(loc, vertical_distance)) {
             vertical_distance = 0.0f;
         }
         int32_t angle = wrap_360_cd(loc.get_bearing_to(peer_loc) - ahrs.yaw_sensor);
-        if (distance < 2.0f) {
+        int16_t relative_angle = wrap_360_cd((peer_heading * 100) - ahrs.yaw_sensor);
+        if (distance < 2.0f)
+        {
             //avoid fast rotating arrow at small distances
             angle = 0;
         }
         char arrow = get_arrow_font_index(angle);
-        backend->write(x, y, false, "%c%c", id + 65, arrow);
-        draw_distance(x+2, y, distance);
-        draw_vdistance(x+1, y+1, vertical_distance);
+        char relative_arrow = get_arrow_font_index(relative_angle);
+        backend->write(x, y, false, "%c%c", relative_arrow, id + 65);
+        draw_vdistance(x+2, y, vertical_distance);
+        backend->write(x, y+1, false, "%c", arrow);
+        draw_distance(x+1, y+1, distance);
     } else {
         backend->write(x, y, true, "%c", id + 65);
     }
     if (AP_HAL::millis() - last_peer_change > 2000) {
         id = ap_radar->get_next_healthy_peer(id);
-	last_peer_change = AP_HAL::millis();
+	    last_peer_change = AP_HAL::millis();
     }
 }