a) Keep Track: You can understand how far along the route you’ve come by noting landmarks that you pass. Keep your map facing North and your thumb on your current position, then move your thumb when you reach your next way point.
b) Time: If you know your approximate speed you can calculate how long it should take to travel the distance. For example if your approximate speed is 4km/h it’ll take you 30 minutes to travel 2km.
c) Distance: Count each step with your right foot. If your approximate stride length is 0.8 metres, then it should take you 62 steps to travel 100 metres.