When calculating the distance of a journey on the map you need to remember the actual distance you are going to travel along the ground will be further than the map implies.
The two dimensions of a map don’t show you the actual distances of slopes you will be travelling up and down, adding to the overall distance you walk.
Note: 1 millimetre on the map equates to 50 metres on the ground
You need to know how many double paces it takes you to cover 100 metres
The average person takes approximately 65 double paces, ie, thats everytime the right foot hits the ground.
By counting your paces as you walk, you can judge how far you have travelled. This is obviously useful for night navigation or in bad visibility.
What you have to remember is that different types of terrain will effect your pacing, also going up and downhill.
Slope: Pace lengthens downhill and shortens uphill.
Winds: A tailwind will lengthen your pace, headwinds will shorten.
Surface: Loose surfaces will shorten your pace.
Equipment: Heavy burdens will shorten the pace.
Stamina: Fatigue will shorten the pace.
Visibility: Bad visibility, or at night will shorten the pace.
This method quite simple, just imagine how many footbal fields you could fit in between you and your objective.
This is one of the methods that we used to use in the Army and I have practiced it with Coastguard Rescue Teams who found out how accurate it could be.
Each member of the group comes up with what they think is the distance to the objective. One person then adds up all the totals (Prefarably the one whos good at maths) then divide the total amount by the number of group members.