After the user steps, the same movement only stays the same command if the distance frame is nailed

What it is

People slide half a metre on a sofa, step closer, sit sideways. Distance from hand to sensor and from hand to body both change. The coordinate anchor decides whether a “twenty centimetres right” swipe is relative to the room, to the device, or to the shoulder of this moment. The wrong anchor makes amplitude mapping, hit distance, even direction change after a shift, and people say “it just worked.” Consistency at the distance layer comes before the details of how a volume is hung on a device or a body. Ask first: after a move, is the same bodily action still the same command.

Why it happens

In absolute space, hand displacement is body displacement plus displacement relative to the shoulder. If the system reads swipe from hand speed in room coordinates, walking contaminates the gesture. If speed is taken relative to shoulder or head, walking subtracts out and a swipe after a walk still looks like a swipe. The cost: a wrong shoulder estimate drifts the whole relative frame. Distance likewise: “please stand at two metres” with a device origin becomes “you are now too close” once the person sits. “Operate at chest height” with a body origin lets people change seats, but a hand behind the torso is then through its own near edge. Consistency is the anchor not moving on a stance change, not a smarter recognizer.

Studying it

Have people produce the same swipe and the same pinch from three stances: comfortable centre distance, half a metre to the side, one step forward and back. Compare recognition, amplitude mapping (how far the UI travelled for the same throw), and whether it “still felt like the same move.” The factor is the anchor: device origin vs shoulder origin vs origin frozen at engagement. Gesturing while walking as a stress condition. Do not measure only on a marked floor sticker.

Where it stops holding

A fixed seat and a fixed headset barely challenge the anchor; laboratories will underestimate this. With several people, each needs their own anchor, or the person who stepped closer rewrites the distant person's distance scale. In an elevator or a car the device origin itself moves, a room anchor dies, and a body anchor is required. Whether the anchor freezes at engagement or keeps following changes the time structure of consistency—that is a finer layer. At the distance layer, pick one and remeasure after a shift.

Applying it

• Spec what swipe/pinch displacement is relative to: device, shoulder, or a position frozen at entry.
• Acceptance includes a side shift and a step forward/back. If mapping or recognition jumps with stance, change the anchor before changing the vocabulary.
• If walking use is required, prefer a body anchor, and define what happens when the shoulder is lost and the anchor dies.

Related

• Same group: C4.10.1 Interaction distance should sit inside capture range · C4.10.3 The boundary is invisible, so leaving it and a recognition miss look the same · C4.10.4 Boundary state must be expressed and distinguishable from recognition failure
• Adjacent: C4.21 Coordinate anchors of the interaction volume · C4.15 Conditions for entering engagement
• Search: coordinate frame · body-relative gesture · stance consistency