Encode time as vertical position when 2D overlap hides movement

Move time into a vertical spatial axis when a 2D map view piles different moments on top of the same places. For example, lift spatio-temporal points into a 3D space-time cube so repeated positions over time form a readable trajectory or oscillation instead of a flat overlapping cloud.

Separating time from map position lets viewers see sequence and motion directly rather than infer it from overlapping marks or weak brightness changes. The paper contrasts a crowded 2D spatio-temporal view with a 3D view where the vertical time axis makes the movement pattern visible.

Mechanism: The extra axis creates spatial separation for successive time points, so order and repeated movement become visible as structure instead of staying hidden inside overplotting.

Evidence: The paper argues that the third dimension can make time more visibly distinguishable than 2D brightness coding, and its space-time example shows that vertical time encoding reveals oscillation that is hard to perceive in the overlapping 2D view (Brath, 2014).

• User Goal: Reconstruct motion or sequence through geographic space.
• Task: See what came before and after, and identify repeated or oscillating movement.
• Data: Time-stamped locations or geotemporal point data.
• Chart Setting: A mapped point or trajectory display where multiple times occupy the same or nearby positions.
• Audience: Readers who need pattern visibility more than a flat map-only view.
• Success Criterion: Movement order is visible directly from the geometry rather than inferred from overlapping points.

Break it when: The 3D points are effectively non-anchored and the scene lacks enough cues to decode depth. Why: The paper notes that random 3D point locations cannot be determined reliably without additional perspective cues or supportive data structure.

Sacrifice: You give up the simplicity of a flat map. Risk: Readers may struggle with depth if the 3D scene does not provide enough positional cues. Mitigation: Use this move where the temporal structure itself or other scene cues make the 3D position readable.

Mistake: Leave time in a 2D overlapping map and try to rescue the sequence with brightness alone. Why it fails: The ordering and movement pattern remain hard to perceive when points occupy the same space.

Failure Sign: Readers can see where points are but cannot tell the direction, repetition, or oscillation over time. Quick Check: Ask whether the temporal path is visible from the geometry itself rather than from labels or memory. Stronger Test: Compare the same data in a 2D overlapping map and in a 3D vertical-time view, then inspect which one makes the movement pattern directly readable.

• Add a vertical axis dedicated to time.
• Separate repeated locations by placing successive time points at different heights.
• If the lifted points still feel ambiguous, add stronger depth cues or use a view whose data structure gives clearer spatial cues.