Real river geometry, not a straight-line guess.
Where the Dunajec forms the Slovak-Polish border
17 km
Of the Dunajec's roughly 249 km, only this 17 km stretch actually forms the border, through the Pieniny Środkowe range east of the Czorsztyn reservoir. The rest of the river runs entirely within Poland.
Windiest route: Rafting from port Sromowce Wyżne to Krościenko, sinuosity 3.11× - the water travels over 3x further than a straight line would.
Per-route breakdown
The app's stored estimate for the same 7 routes adds up to 95.8 km - a haversine-based approximation, not traced river geometry.
Sinuosity index
Real channel length ÷ straight-line distance between start and end. A standard river-geomorphology measure of how much a river winds: 1.0 is dead straight, 2.0+ is classified "extreme meandering". Every one of these 7 routes clears 2.0.
Elevation drop
Real elevation drop and average gradient along each route, from Copernicus EU-DEM (25m). A coarser global elevation dataset was tried first and gave physically impossible results (the river appearing to flow uphill) in this narrow, steep-walled gorge - switched datasets and re-verified before shipping this.
River shape traced from real OpenStreetMap river-way data. Each route's start and end point is projected onto the actual river centerline, and the real distance between those two points is measured along the water, following every bend. Elevation from Copernicus EU-DEM (25m resolution).