clover: add GPS usage example

clover/examples/gps.py

@@ -0,0 +1,47 @@
+# Information: https://clover.coex.tech/en/simple_offboard.html#navigateglobal
+
+import rospy
+from clover import srv
+from std_srvs.srv import Trigger
+import math
+
+rospy.init_node('flight')
+
+get_telemetry = rospy.ServiceProxy('get_telemetry', srv.GetTelemetry)
+navigate = rospy.ServiceProxy('navigate', srv.Navigate)
+navigate_global = rospy.ServiceProxy('navigate_global', srv.NavigateGlobal)
+set_position = rospy.ServiceProxy('set_position', srv.SetPosition)
+set_velocity = rospy.ServiceProxy('set_velocity', srv.SetVelocity)
+set_attitude = rospy.ServiceProxy('set_attitude', srv.SetAttitude)
+set_rates = rospy.ServiceProxy('set_rates', srv.SetRates)
+land = rospy.ServiceProxy('land', Trigger)
+
+# https://clover.coex.tech/en/snippets.html#wait_arrival
+def wait_arrival(tolerance=0.2):
+    while not rospy.is_shutdown():
+        telem = get_telemetry(frame_id='navigate_target')
+        if math.sqrt(telem.x ** 2 + telem.y ** 2 + telem.z ** 2) < tolerance:
+            break
+        rospy.sleep(0.2)
+
+start = get_telemetry()
+
+if math.isnan(start.lat):
+    raise Exception('No global position, install and configure GPS sensor: https://clover.coex.tech/gps')
+
+print('Start point global position: lat={}, lon={}'.format(start.lat, start.lon))
+
+print('Take off 3 meters')
+navigate(x=0, y=0, z=3, frame_id='body', auto_arm=True)
+wait_arrival()
+
+print('Fly 1 arcsecond to the North (approx. 30 meters)')
+navigate_global(lat=start.lat+1.0/60/60, lon=start.lon, z=start.z+3, yaw=math.inf, speed=5)
+wait_arrival()
+
+print('Fly to home position')
+navigate_global(lat=start.lat, lon=start.lon, z=start.z+3, yaw=math.inf, speed=5)
+wait_arrival()
+
+print('Land')
+land()