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* 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)
29 lines
1.8 KiB
Markdown
29 lines
1.8 KiB
Markdown
Coordinate systems (frames)
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===
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> **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.
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Main frames in the `clever` package:
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* `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;
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* `base_link` is rigidly bound to the drone. It is shown by the simplified drone model on the image above;
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* `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;
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* `navigate_target` is bound to the current navigation target (as set by the [navigate](simple_offboard.md#navigate) service).
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> **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.
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3D visualization of the coordinate systems can be viewed using [rviz](rviz.md).
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tf2
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--
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Read more at http://wiki.ros.org/tf2
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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.
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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.
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tf2 can be used from Python to transform coordinates (for objects like PoseStamped and PointStamped) from one frame to another
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