Time and Energy is often more important than Distance
You are out on a trek. It’s 9:30 am. The sign at the trail start says there is a great lake just 1.5 kilometres from the camp you are staying at. Easy enough for you and children in the group to do with you and be back at camp for lunch. No need to take food with. Right? It’s only 3 kilometres return. Even at a child’s pace that’s only 2 hours.
What the sign does not tell you is the lake is 300 meters higher than where you are now, and gaining altitude takes energy.
As you gain altitude each 100 meters of ascent uses the same energy as walking between 1.5 to 2 kilometers depending on your walking speed. So that 300 meters ascent will equate to 4.5 to 6 kilometers extra “Energy kilometers”.
Assuming the distance to the lake is 1.5 km each way, that makes it 3 km total, but now we add the energy kilometres needed for the altitude gain which is an additional 4.5 to 6 kilometres. (We only count the up hills)
So now the trip to the lake is going to be a total of between 6 to 9 “Energy Kilometers”. Can you and the children do that before lunch without having substantial drinks and snacks along the way?
A child walking at 1.5 kilometres an hour is now going to take between 4.5 and 6 hours. An adult will take 1.5 to 2.5 hours.