A worked example of how Verdant Ride checks a leaderboard time. One 23-minute session — “Xanten (105)”, 24 August 2026 — plotted over satellite imagery and OpenStreetMap, so land and water are unambiguous.
The whole session sits on Xantener Nordsee, a flooded gravel lake at Xanten, North Rhine-Westphalia (51.6956°N, 6.4299°E). Launch is the beach beside Hafen Wardt on the south shore. 8.34 mi of laps, all of it on open water. Every metre of this session is exactly where an eFoil session should be.
The board lost GPS for 63 seconds and came back 350 m away, on the dike path along the northeast shore. The Fastest Minute window opens right there. Its first 16.5 seconds are a dead-straight 522 m line back across the lake — 70 mph average — while the board’s own speed sensor reads 0.0 mph the whole way. That is a receiver crawling home from a bad fix, not a rider.
Fliteboard writes its own speed onto every track point. Where the receiver is healthy the two agree almost exactly — the raw GPS figures just alternate high/low every half-second, and averaging two consecutive samples lands within 1 mph of the sensor. Where the receiver is not healthy, the sensor reads 0.0 and the positions go to fantasy.
| Time | GPS-derived | Board sensor | Step | What it is |
|---|---|---|---|---|
| 958.5 s | 112.4 mph | 0.0 mph | 20.6 m | re-lock walk-back, on land |
| 960.0 s | 121.2 mph | 0.0 mph | 11.7 m | re-lock walk-back |
| 965.0 s | 19.7 mph | 23.3 mph | 6.3 m | healthy — low half of the zigzag |
| 965.5 s | 28.1 mph | 24.2 mph | 4.2 m | healthy — high half of the zigzag |
| 973.0 s | 303.7 mph | 0.0 mph | 45.1 m | second dropout |
| 988.0 s | 26.8 mph | 33.4 mph | 9.0 m | healthy, fastest clean stretch |
Nobody did anything wrong here. This is a normal 23-minute session on a lake, on a board whose receiver dropped out twice — something every GPS device on the market does. Our Fastest Minute algorithm read the recovery as speed and published a number no eFoil has ever recorded. That is our bug to fix, not the rider’s.
It also shows why throwing out the whole ride is the wrong fix. Of the 121 fixes in that minute, 15 are garbage and 106 are fine, and the other 22 minutes of the session are clean. Reject the bad steps, keep the ride.
The clean fixes also confirm the sensor is the better source. Where the receiver is healthy the raw GPS speed alternates high–low every half second — 19.7, 28.1, 19.7, 28.1 — which is a sampling artifact, not the rider surging twice a second. Average any two consecutive samples and you get 23.9 mph. The board says 24.2. That is the whole case for reading <gpxtpx:speed> first and falling back to positions only when it is absent.