XSD: add scaling value 2E-3

[hamishwillee]

Allow efficient scaling of a % value in UINT16 value. With this, 0 to 100 is represented by 50000.

This is needed for https://github.com/mavlink/mavlink/pull/2526/changes#r3465455513 - but would do no harm anyway.

[peterbarker]

This works, but why not the full range? Leaving room for flag "not supplied values, of course.

I also suggest making the soc 0-1 rather than as a percentage to make things simpler. Usually that will be scaled to a percentage, but it may not need to go via that before the GCS renders a little "gauge" icon, for example.

We're trying to move away from percentages generally in ArduPilot, preferring a scaler of 0-1 (or -1 to 1 in places...)

[hamishwillee]

@peterbarker There's literally no difference in the data conveyed by a scaled percentage or a normalized value from 0 to 1, so if you want to call SoC a normalized scaled value then go for it :-).

I'm opposed to scaling across the full range though because it makes the maths a little bit harder, and a lot less intuitive. You could argue that doesn't matter, but I think it increases the chance for error.

If the argument is that the extra range gained from scaling from 50K up to 64K ish will make a difference, then you're arguing that it makes sense to move back to a float :-)

EDIT PS This is just my opinion. You're welcome to take this to the dev call since we're not getting this resolved right now unless you agree with me. I would like to come out of the call on Wednesday with agreement that this is the message. 3 years is a long wait.

[peterbarker]

On Thu, 25 Jun 2026, Hamish Willee wrote: If the argument is that the extra range will make a difference, then you're arguing that it makes sense to move back to a float :-)

Yeah, I don't think *that* logics ;-)

[hamishwillee]

Yeah, I don't think that logics ;-)

I'm sure you get my point

• if we don't need the extra resolution, choosing to provide it should be balanced against the calculation cost, ease of scaling, and so on.
• if we really do need more resolution it is unlikely that increasing the range by 15% oir whatever it is will be sufficient long time.

I know I'd prefer to work with numbers that are easy to convert to decimal unless there is real value in it.