Introduction to Topographic Maps

SPEAKER: Hi everybody!

Today we're going to take a look at
topographic maps, and I'm going to

teach you how to read them, and we're
going to go through some of the rules`

that will help them make sense.

So right now you're looking at a
topographic map, and it probably

looks like a bunch of squiggles and
lines and colours.

Probably does not make too much sense
to you.

Here's another topographic map, the same
thing, probably just looks like a bunch of

brown squiggles with some other colours
thrown in there.

By the end of the video, hopefully you're
going to be able to look at a map like this

and you're going to be able to see the
topography, or the shape of the land.

So a topographic map looks like this one
on the bottom, and basically what they do

is they are a map that is able to show us
the elevation, the height above sea level,

and the shape of the land by using these
lines, which are a kind of isoline,

called contour lines.

So on the top we have a landscape, you
can see there's a cliff over here, there's

a hill over here.

When you know how to read a topographic
map you can actually look at this and

you can tell that there's a cliff over
here and there's a hill over here.

Topographic maps have certain features
that you will always see, so let's go

through 4 of those features.

The first thing you're going to have to
figure out is what the contour interval is.

When you look at a topographic map, you'll
notice that not every line is labelled.

For example, this map, we have 300
labelled, we have 400 labelled.

Those lines are a little bit darker than
the surrounding lines.

Those numbered lines are called index
contour lines, the reason they only

label some of them is because we don't
want the map to be too confusing,

we don't want numbers everywhere.

So, the first thing you have to do is
figure out what the contour interval is.

In other words, what is the difference
between each pair of lines?

Now, sometimes they'll tell you the
interval in a key under the map, but

more often than not you're gonna have to
determine it yourself.

So if we start with this map over here,
again we have 300 and it's

either meters or feet or kilometers,
we're not sure with this map because it

doesn't tell us.

But we have 300 here, we have 400 here.

So our task is to figure out what the
contour interval is, what are we gonna

count by to get to 300 to 400?

Now, hopefully, you're looking at this
and you're realizing, well, it's a

difference of 100 and it's spread out
over 5 lines, so 100 divided by 5

is 20.

So for this map the contour interval
would be 20 units.

So by units, we mean either miles or
kilometers or meters.

Let's take a look at this top left map
over here.

So we're going from 20, and then we're
skipping a line, it's not labelled, then

we're going to 20.

So that one's pretty easy, we're
counting by 5's.

The bottom left map over here, okay, I
see that this contour line is labelled

as 50, and this contour line up here is
labelled as 100.

So, again, it goes from 50 to 100, which
is a difference of 50, and it's going

5 lines between them, so 50 divided by
5 is 10.

And then on the last map, this one's
pretty easy to figure out.

We're counting by 25's, so our contour
interval would be 25 whatever unit is

being used.

Let's take a look at another map.

Can you figure out on this map what
the contour interval would be?

And feel free to pause the video.

Well hopefully you realized that we're
going from 500 to 600, so we're going

a difference of 100, and again we're
spreading it out over 5 lines so we're

counting with an interval of 20 meters.

Once you know the interval, you can now
figure out the elevation of any of the

lines that are not labelled.

So, for example, line A, right over
here, if we're counting by 20's, this`

line would be 540 meters.

I want you to see if you could figure out
what the elevation of line B would be.

So think about that for a second.

And hopefully, you're realizing that
it's 580 meters.

Okay, so again: contour interval, first
thing you want to figure out.

The next thing that you'll notice on
most maps is somewhere there will be a

compass rose, and that's important
because that will show you where North is.

And normally when we look at a map, North
is usually up, but that is not always

the case.

You can see on this map that they're
telling you that north is facing the right

side of the map, so North is really here
and then South would be over here.

So you want to look at the compass rose,
you want to figure out where North is,

where South is.

So, let's go through some of the rules of
how to read a topographic map, okay.

Going back to this first map that we
looked at earlier.

I want you to notice when there's a cliff,
what the contour lines look like.

So right over here, where the land is
steep, you probably notice that the

contour lines are very close together,
and that's always going to be the case.

Rule #1 is: the closer the lines are, the
steeper the slope.

Or, the opposite, the more spread out
the lines are, the gentler the slope.

We can see on the side of this hill over
here we have a nice flat area, uh,

right over here, the land is pretty flat
over here and on our contour map we can

see the lines are spread apart much
further than they were over there.