navigator: allow mission items with same position

This reverts the addition of a check against mission items that have the
same position. This breaks existing MAVSDK implementations where a
LOITER_TIME item is set right after a WAYPOINT with the same
coordinates. It is an interim hack to allow the vehicle to hold still
during a photo is captured.

This leaves the check in place for gates where we need to be able to
calculate the direction between gate and waypoint.

src/modules/navigator/mission_feasibility_checker.cpp

@@ -676,7 +676,6 @@ MissionFeasibilityChecker::checkDistancesBetweenWaypoints(const mission_s &missi
 
 	double last_lat = (double)NAN;
 	double last_lon = (double)NAN;
-	float last_alt = NAN;
 	int last_cmd = 0;
 
 	/* Go through all waypoints */
@@ -715,15 +714,16 @@ MissionFeasibilityChecker::checkDistancesBetweenWaypoints(const mission_s &missi
 
 				/* do not allow waypoints that are literally on top of each other */
 
-			} else if ((dist_between_waypoints < 0.05f && fabsf(last_alt - mission_item.altitude) < 0.05f) ||
+				/* and do not allow condition gates that are at the same position as a navigation waypoint */
-				   /* and do not allow condition gates that are at the same position as a navigation waypoint */
+
-				   (dist_between_waypoints < 0.05f && (mission_item.nav_cmd == NAV_CMD_CONDITION_GATE
+			} else if (dist_between_waypoints < 0.05f &&
-						   || last_cmd == NAV_CMD_CONDITION_GATE))) {
+				   (mission_item.nav_cmd == NAV_CMD_CONDITION_GATE || last_cmd == NAV_CMD_CONDITION_GATE)) {
-				/* waypoints are at the exact same position,
+
-				 * which indicates an invalid mission and makes calculating
+				/* Waypoints and gate are at the exact same position, which indicates an
-				 * the direction from one waypoint to another impossible. */
+				 * invalid mission and makes calculating the direction from one waypoint
+				 * to another impossible. */
 				mavlink_log_critical(_navigator->get_mavlink_log_pub(),
-						     "Distance between waypoints too close: %d meters",
+						     "Distance between waypoint and gate too close: %d meters",
 						     (int)dist_between_waypoints);
 
 				_navigator->get_mission_result()->warning = true;
@@ -733,7 +733,6 @@ MissionFeasibilityChecker::checkDistancesBetweenWaypoints(const mission_s &missi
 
 		last_lat = mission_item.lat;
 		last_lon = mission_item.lon;
-		last_alt = mission_item.altitude;
 		last_cmd = mission_item.nav_cmd;
 	}