docs: translation updates (#186)

* docs: Update frames article (en)

* docs: Add navigate_target notes to simple_offboard (en)

* docs: Update note about single-marker navigation

* docs: Add note about auto parameters in PX4 (en)

docs/en/aruco_map.md

@@ -61,6 +61,8 @@ Usage example:
 rosrun aruco_pose genmap.py 0.33 2 4 1 1 0 > ~/catkin_ws/src/clever/aruco_pose/map/test_map.txt
 ```
 
+You can also use the [online map editor](arucogenmap.md) to create ArUco maps.
+
 ### Checking the map
 
 The currently active map is posted in the `/aruco_map/image` ROS topic. It can be viewed using [web_video_server](web_video_server.md) by opening the following link: http://192.168.11.1:8080/snapshot?topic=/aruco_map/image
@@ -102,6 +104,12 @@ If you're using **LPE** (`SYS_MC_EST_GROUP` parameter is set to `local_position_
 * Vision position standard deviations: `LPE_VIS_XY` = 0.1 m, `LPE_VIS_Z` = 0.1 m.
 * `LPE_VIS_DELAY` = 0 sec.
 
+<!-- * Compass should not be fused: `ATT_W_MAG` = 0 -->
+
+> **Hint** We recommend using **LPE** for marker-based navigation.
+
+You may use [the `selfcheck.py` utility](selfcheck.md) to check your settings.
+
 > **Hint** In order to use LPE with the Pixhawk v1 hardware you should download the [`px4fmu-v2_lpe.px4` firmware](firmware.md)
 
 ## Flight
@@ -120,10 +128,13 @@ time.sleep(5)
 navigate(x=2, y=2, z=2, speed=1, frame_id='aruco_map')
 ```
 
-Starting from the [image](image.md) version 0.18, the drone also can fly relative to a marker in the map, even if it doesn't see it:
+### Using a specific marker frame
+
+Starting with the [image](image.md) version 0.18, the drone also can fly relative to a marker in the map, even if it is not currently visible. Like with [single-marker navigation](aruco_marker.md#working-with-detected-markers), this works by setting the frame_id parameter to aruco_ID, where ID is the desired marker number.
+
+The folloding code will move the drone to the point 1 meter above the center of marker 5:
 
 ```python
-# Fly to 1 meter above the marker 5
 navigate(frame_id='aruco_5', x=0, y=0, z=1)
 ```
 

docs/en/frames.md

@@ -1,16 +1,28 @@
 Coordinate systems (frames)
 ===
 
-> **Note** Documentation for the [image](image.md), versions, starting with **0.15**. For older versions refer to [documentation for version **0.14**](https://github.com/CopterExpress/clever/blob/v0.14/docs/ru/frames.md).
+> **Note** The following applies to [image](image.md) version 0.15 and up. See [previous version of the article](https://github.com/CopterExpress/clever/blob/v0.14/docs/ru/frames.md) (Russian only) for older images.
 
-![Clever coordinates systems (TF2)](../assets/frames.png)
+![TF2 Clever frames](../assets/frames.png)
 
-Main frames in package `clever`:
+Main frames in the `clever` package:
 
-* `map` coordinates relative to the point of flight controller initialization: the white grid in the illustration;
-* `base_link` — coordinates relative to the quadcopter: schematic image of the quadcopter in the illustration;
-* `body` — coordinates relative to the quadcopter regardless of pitch and roll: red, blue and green lines in the illustration.
+* `map` has its origin at the flight controller initialization point and may be considered stationary. It is shown as a white grid on the image above;
+* `base_link` is rigidly bound to the drone. It is shown by the simplified drone model on the image above;
+* `body` is bound to the drone, but its Z axis points up regardless of the drone's pitch and roll. It is shown by the red, blue and green lines in the illustration;
+* `navigate_target` is bound to the current navigation target (as set by the [navigate](simple_offboard.md#navigate) service).
 
-> **Hint** In accordance with [the agreement](http://www.ros.org/reps/rep-0103.html), for frames associated with the copter, the X-axis directed forward, Y – to the left, and Z – up.
+> **Hint** Frames that are bound to the drone are oriented according to [the ROS convention](http://www.ros.org/reps/rep-0103.html): the X axis points forward, Y to the left, and Z up.
 
-More clearly, 3D visualization of the coordinate systems can be viewed using [rviz](rviz.md).
+3D visualization of the coordinate systems can be viewed using [rviz](rviz.md).
+
+tf2
+--
+
+Read more at http://wiki.ros.org/tf2
+
+tf2 ROS package is used extensively in the Clever platform. tf2 is a set of libraries for C++, Python and other programming languages that are used to work with the frames. Internally, ROS nodes publish `TransformStamped` messages to `/tf` topic with transforms between frames at certain points in time.
+
+The [`simple_offboard`](simple_offboard.md) node can be used to request the drone position in an arbitrary frame by setting the `frame_id` argument appropriately in a call to `get_telemetry` service.
+
+tf2 can be used from Python to transform coordinates (for objects like PoseStamped and PointStamped) from one frame to another

docs/en/optical_flow.md

@@ -20,6 +20,8 @@ Optical Flow publishes data in `mavros/px4flow/raw/send` topic. In the topic `op
 
 ## Setup of the flight controler
 
+> **Hint** Suggested parameters are applied automatically in [our custom PX4 firmware](firmware.md#modified-firmware-for-clever).
+
 When using **EKF2** (parameter `SYS_MC_EST_GROUP` = `ekf2`):
 
 * `EKF2_AID_MASK` – flag 'use optical flow' is on.

docs/en/simple_offboard.md

@@ -1,11 +1,11 @@
 Simple OFFBOARD
 ===
 
-> **Note** Documentation for the [image](image.md), versions, starting with **0.15**. For older versions refer to [documentation for version **0.14**](https://github.com/CopterExpress/clever/blob/v0.14/docs/ru/simple_offboard.md).
+> **Note** The following applies to [image](image.md) versions **0.15** and up. Older documentation is still avaliable [for version **0.14**](https://github.com/CopterExpress/clever/blob/v0.14/docs/ru/simple_offboard.md) (Russian only).
 
 <!-- -->
 
-> **Hint** For autonomous flights it is recommanded to use [special PX4 firmware for Clever](firmware.md#modified-firmware-for-clever).
+> **Hint** We recommend using our [special PX4 firmware for Clever](firmware.md#modified-firmware-for-clever) for autonomous flights.
 
 The `simple_offboard` module of the `clever` package is intended for simplified programming of the autonomous drone flight (`OFFBOARD` [flight mode](modes.md)). It allows setting the desired flight tasks, and automatically transforms [coordinates between frames](frames.md).
 
@@ -140,6 +140,12 @@ Flying 3 m to the right from the drone:
 navigate(x=0, y=-3, z=0, speed=1, frame_id='body')
 ```
 
+Flying 2 m to the left from the last navigation target:
+
+```python
+navigate(x=0, y=2, z=0, speed=1, frame_id='navigate_target')
+```
+
 Turn 90 degrees counterclockwise:
 
 ```python
@@ -170,6 +176,8 @@ Ascending to the altitude of 2 m (command line):
 rosservice call /navigate "{x: 0.0, y: 0.0, z: 2, yaw: 0.0, yaw_rate: 0.0, speed: 0.5, frame_id: 'body', auto_arm: true}"
 ```
 
+> **Note** Consider using the `navigate_target` frame instead of `body` for missions that primarily use relative movements forward/back/left/right. This negates inaccuracies in relative point calculations.
+
 ### navigate_global
 
 Flying in a straight line to a point in the global coordinate system (latitude/longitude).

docs/ru/aruco_map.md

@@ -128,16 +128,9 @@ time.sleep(5)
 navigate(x=2, y=2, z=2, speed=1, frame_id='aruco_map')  # полет в координату 2:2, высота 3 метра
 ```
 
-Начиная с версии [образа](image.md) 0.18, доступны также полеты относительно отдельного маркера в карте, даже если дрон его не видит:
-
-```python
-# Полет на высоту 1 м над маркером 5
-navigate(frame_id='aruco_5', x=0, y=0, z=1)
-```
-
 ### Полет в координаты по ID маркера
 
-По аналогии с [навигацией по отдельным маркерам](aruco_marker.md#навигация-по-маркерам) при настройке карты маркеров дрон сможет лететь в координаты относительно отдельного маркера, используя фрейм aruco_ID с соответствующим ID маркера. Эта функция будет работать даже в случае, если дрон не видит в данный момент нужный маркер.
+Начиная с версии [образа](image.md) 0.18, доступны также полёты относительно отдельного маркера в карте, даже если дрон его не видит. По аналогии с [навигацией по отдельным маркерам](aruco_marker.md#навигация-по-маркерам) при настройке карты маркеров дрон сможет лететь в координаты относительно отдельного маркера, используя фрейм aruco_ID с соответствующим ID маркера.
 
 Полет в точку над маркером 5 на высоту 1 метр: