Do not use the term "world frame"

[ufechner7]

Please, use only reference frames that are defined in our documentation: https://opensourceawe.github.io/KiteUtils.jl/dev/reference_frames/

So we have:

• SE for small earth reference frame
• W for wind reference frame
• EX for earth xsense reference frame
• KS for kite sensor reference frame
• EG: for NorthWestUp (earth ground) reference frame
• ENU for East North Up reference frame

In addition, in VortexStepMethod.jl https://opensourceawe.github.io/VortexStepMethod.jl/dev/reference_frames/ is defined:

• CAD reference frame
• KB (kite body) reference frame

[1-Bart-1]

In the documentation it says:

For position and velocity vectors of the model the ENU (East North Up) reference frame is used.

But ENU is a convention, not a frame. You can use ENU for the kite body frame as well, for example.
Instead of saying ENU is a frame, the frame could either be called the global frame or the world frame. I propose:

For position and velocity vectors of the model in the world frame, the ENU (East North Up) convention is used.

[1-Bart-1]

Reference frames could be as simple as saying that everything that has an orientation also gets a frame:

kite_body
sensor_body - usually has the x y and z directions written on the physical unit
winch_body - z along drum axis

And then one world frame
world or global (using the ENU convention)

[ufechner7]

Well, we have the convention to use two or three capital letters to describe the reference frames, and then we have functions like fromENU2EG() that convert a vector from one reference frame to another: https://opensourceawe.github.io/KiteUtils.jl/dev/functions/#Coordinate-system-transformations .

Currently I don't see any good reason to change that convention.

But we also have the functionenu2ned() which is inconsistant.

[1-Bart-1]

I use rotations like R_b_w in my code to rotate from body to world frame. I find this intuitive and easy to use, and I use it because I found the different frames confusing.

[1-Bart-1]

we have functions like fromENU2EG() that convert a vector from one reference frame to another

Both ENU and EG are world frames with different conventions. Switching between them is not the same as using for example R_b_w which rotates from a local body frame to a world frame.

[1-Bart-1]

Having a body/local and world frame is used in Multibody.jl as well. For clarity in the code, world frame is good. We can update the docs, but for that we should create a different issue.

https://github.com/JuliaComputing/Multibody.jl/blob/8e3f8c1eb3e37a48a37247ba187a402db42dfee5/src/components.jl#L16C1-L16C200

[ufechner7]

You cannot close this issue. We need to discuss that in a call.

[1-Bart-1]

This package is more like a compiler than a specific kite model implementation. So in the yaml file you define:
z_ref_points: [1, [12, 11]] # KCU to LE for Z (normal)
y_ref_points: [12, 10] # Center LE for Y (span)
These define your reference frame. So the user decides which frame from KiteUtils.jl is used. In the package we don't know in advance which frame the user decides to use, so we cannot give them specific names.

[1-Bart-1]

I will keep using the term world frame.