Geographers developed a series of models that strongly predict how terrain slope impacts travel rates. Using a crowdsourced fitness-tracking database, they analyzed GPS data from nearly 30,000 people.

Slew rate is the slope of the waveform, calculated as ΔV/Δt. Fig. 2 shows the ΔV/Δt calculation at the 10% and 90% points, but the calculation can be done at any location on the waveform. ... Yes, ...

Here, on Colorado’s Western Slope, no snow means no snowpack. And no snowpack means no water in an area that’s so dry it’s lucky to get 10 inches of rain a year.