Name: GAP Segment Predictor
Author: ololof

Predict exactly when you'll finish a hilly segment — using Grade Adjusted Pace (GAP), not raw pace.

Flat-ground pace predictions fall apart on rolling or climbing terrain: a tough climb early in a segment throws off any simple "time = distance / current pace" estimate. This data field fixes that by tracking your effort in GAP terms throughout the segment, then projecting your remaining time based on how much distance and elevation gain you have left.

HOW IT WORKS

Press Lap to start a new prediction — the field resets and begins tracking distance, elevation gain, and grade-adjusted pace from that moment. As you run, it continuously re-estimates your grade-adjusted effort using a standard running energy-cost model (Minetti et al.), so a slow uphill stretch and a fast downhill stretch are weighted correctly instead of throwing off your pace average. Your remaining time is projected by assuming the elevation gain left in your segment settings is spread over the distance left, at your current GAP effort.

ON SCREEN

• Predicted finish time — large, front and center
• Distance done / distance left
• Elevation gained / elevation left
• Elapsed time / time left
• Average GAP and average raw pace
• The actual pace you need to hold for the rest of the segment to hit your predicted time

SETTINGS

• Segment distance (km) — default 2.76 km
• Segment elevation gain (m) — default 192 m

Set these once for your regular hilly loop, interval, or race segment, then just press Lap at the start each time.

WHO IT'S FOR

Built for runners who train on hilly or rolling segments where flat-pace math doesn't hold up — hill repeats, trail loops, or any repeated segment with real elevation change. If you've ever crested a hill with no idea whether you're on pace, this field is for you.

All distances and paces are shown in kilometers, and the layout automatically adapts to your watch's screen shape and the field size you assign it.