Tobler's hiking function – walking speed vs. slope angle chart.
Tobler's hiking function is an exponential function determining the hiking speed, taking into account the slope angle. It was formulated by Waldo Tobler. This function was estimated from empirical data of the Swiss cartography professor Eduard Imhof.
Formula
Walking velocity:
where
W = walking velocity [km/h]
dh = elevation difference,
dx = distance,
S = slope,
θ = angle of slope (inclination).
The velocity on the flat terrain is 5km / h, the maximum speed of 6km / h is achieved roughly at -2.86°.
On flat terrain this formula works out to 5km/h. For off-path travel, this value should be multiplied by 3/5, for horseback by 5/4.
Pace
Pace is the reciprocal of speed. For Tobler's hiking function it can be calculated from the following conversion:
where
p = pace [s/m]
m = gradient uphill or downhill (dh/dx = S in Tobler's formula),
12Magyari-Sáska, Zsolt; Dombay, Ştefan (2012). "Determining minimum hiking time using DEM"(PDF). Geographia Napocensis. Anul VI (2). Academia Romana − Filiala Cluj Colectivul de Geografie: 124–129. Retrieved 21 March 2013.