docs: add wait_arrival snippet

docs/en/snippets.md

@@ -13,6 +13,10 @@ Python
 Flying towards a point and waiting for copter's arrival:
 
 ```python
+import math
+
+#...
+
 def navigate_wait(x=0, y=0, z=0, yaw=float('nan'), speed=0.5, frame_id='', auto_arm=False, tolerance=0.2):
     navigate(x=x, y=y, z=z, yaw=yaw, speed=speed, frame_id=frame_id, auto_arm=auto_arm)
 
@@ -55,6 +59,23 @@ Usage:
 land_wait()
 ```
 
+### # {#wait_arrival}
+
+Wait for copter's arrival to the [navigate](simple_offboard.md#navigate) target:
+
+```python
+import math
+
+# ...
+
+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)
+```
+
 ### # {#get_distance}
 
 Calculating the distance between two points (**important**: the points are to be in the same [system of coordinates](frames.md)):

docs/ru/snippets.md

@@ -22,6 +22,10 @@ Python
 Полет в точку и ожидание окончания полета:
 
 ```python
+import math
+
+# ...
+
 def navigate_wait(x=0, y=0, z=0, yaw=float('nan'), speed=0.5, frame_id='', auto_arm=False, tolerance=0.2):
     navigate(x=x, y=y, z=z, yaw=yaw, speed=speed, frame_id=frame_id, auto_arm=auto_arm)
 
@@ -65,6 +69,23 @@ def land_wait():
 land_wait()
 ```
 
+### # {#wait_arrival}
+
+Ожидание окончания прилета в [navigate](simple_offboard.md#navigate)-точку:
+
+```python
+import math
+
+# ...
+
+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)
+```
+
 ### # {#get_distance}
 
 Функция определения расстояния между двумя точками (**важно**: точки должны быть в одной [системе координат](frames.md)):