Everyone who enjoys walking has sometime faced problems with "height gain" :

It could be you come across a hill that you misread as going down rather than up

It could be you are just tired from your activities and do not wish to walk yet more up

Maybe on your route card you forgot to add time for height gain and are now behind time

a height graph of a route is a very useful tool at the planning stage

it allows you to work out where in the day the uphill sections are,
as well as how long they might take

this is an example from a magazine, but it is relatively easy to draw your own

Working out how much time to allow for height
gain

This is worked out using Naismiths rule

if you are unsure about Naismith's rule, see my web page navigation distance

Naismith's Rule for height gain

as well as work out the time taken to walk various distances
you can work out how long it will take to walk uphill

a simple calculation of height gain using Naismith's rule allows 1 minute for each 10 meters of height gain.
the easiest way to do this is to count the contour lines of height gain (check that the contours are 10 meters apart) then add this to the route card

some people a also add time for descent (although this is a matter of personal choice) the formula often used is 1 minute for each 20 metres of descent of average descent.