Hello, and welcome to this lesson of the online course Wilderness Navigation Master, where you will learn to measure distance on your topographic map.
Why you should measure distance on map?
Why this is important to know because when you know the distance from your starting point to your arrival point or from your actual position to the arrival point, you can estimate your travel time, which can help take good choices like not being out in the dark and getting lost easily.
I want you to know that there is more than one method to do that, but because this course is for outdoor enthusiasts like a hiker, hunters, backcountry skiers, etc, I want you to learn with the tools that you will have on you, like the string of your compass or the ruler on the edge of a compass.
Flat map error:
But before going on to show you how to measure distance on a map using both methods, I want you to know that the distance you will get from your flat topographic map is not the same as the actual distance.
Because, due to slopes, the distance on a map is slightly less than what it is in reality, and the more the slope gets steeper, the more the difference get’s bigger.
Is there a solution?
Yes, but it’s not what you can do easily when you are outdoor. For that, it’s better for you to adapt to this, and add some distance to what you get from your topographic map, depending on the slopes you will encounter.
Like I’ve said before, the more the slope is steeper, the more distance you have to add.
Now that you know the importance of measuring distance on a map, the different methods, and the slight difference between what you will get from your map and what is in reality, let’s start with measuring distance using the compass edge ruler method.
Method #1: compass ruler
I have the Rocky Mountain National Park map with the scale of 1:50000, for that, I will use this edge of the compass that has the same scale.
Let’s say that we head to this trailhead named Poudre Lake on our vehicle and we want to hike starting from this little red point to this little redpoint that represents the Alpine Visitor Center.
What I personally do is that I measure every straight line independently as I do in the video below at 2:36.
As you see, I’ve found that this trail measures around (1 km), and when I convert it to miles, it’s 4 miles.
Now let’s check that in the web tool called Caltopo (watch the video below at 3:33).
As you see, it’s a little bit the same thing.
This is the flat, map, distance.
And if you notice, in the first 10% of this trail, we have an elevation gain of 500 feet, and not too much elevation gain over the rest of the trail that we can ignore.
So, my approximate real distance will be 4.2 miles instead of just 4 miles.
That’s all for how to measure distance on a map with the ruler or the edge of your compass, now let’s see the other method that consists of using a map string.
Method #2: using a compass string
Like I’ve said before, I want you to learn how to measure distance with tools that you will have on you most of the time during your outdoor activity, for that, I will show you how to do it using the compass string.
See the video at 5:11
Like you see, using the headphones cable and the map scale bar, I’ve found that it’s around 4.10 miles, it’s a little bit like what I did found using the first method.
So you can rely also on this measurement method.
That’s all, this is how we measure distance on a topographic map. Don’t forget that if you have slopes in your way, you should always convert your flat map distance to the real distance.
Now let’s go to the exercise.
Thank you, and don’t forget that you can share with us in the comments section below what trail you did measure, and how much flat map distance you did found, or just which method you prefer using, the compass string or the compass ruler method?
Thank you again and see you in the next lesson.
Updated on June 7, 2021 by Ben