All language subtitles for 06_contour-maps.en

Contour maps are an effective way of depicting

a three-dimensional surface using two-dimensional flat lines.

So, let's see how we can use contour maps to show surfaces.

So, here I have a satellite image of

Whistler BC which is in a nice beautiful mountainous area.

I've actually never been to Whistler,

so I would really like to go there,

but let's just have a look at it.

So, this would be a way of showing the terrain for that using contours.

So, these green lines represent a 200-meter contour interval.

What that means is that the vertical distance,

the vertical elevation between that line and that line is 200 meters.

Now, the horizontal distance could be

something else depending on the steepness of the slope,

but the vertical distance is 200 meters from there to there,

it's another 200 meters from there to there,

and there to there, and so on.

As you probably are already gathering,

the closer together they are,

the steeper the slope,

and the farther apart they are,

the more gradual the slope.

So, this is a way of being able to depict this terrain,

this three-dimensional surface with

these nice simple lines that we can put on top of our map.

We can vary the interval.

Here we have a 100-foot interval instead of a 200-meter interval,

and since feet are smaller than meters,

we end up with more lines here.

So, there's a good and a bad thing here,

it's that there's more lines which I think is to the point

where it's getting almost a bit distracting especially with this line thickness,

but we are getting a lot more detail in terms of what we're able to see.

So, you can see there's a little peak there and there perhaps, and there.

So, we're getting more detail in terms of the terrain itself,

but you have to be careful because it depends on what the subject if your map is.

Often, if it's a topographic map or a reference map where

the contour lines are just one of many different map layers or themes on the map,

you don't want it to take over the map or to be too obvious.

You want it to be a little more subtle than that,

and so having a 100-foot interval,

it might be useful in our formation depending on your map reader,

but you have to balance that out with how much is it cluttering your map.

For the purpose of comparison,

I've added in a digital elevation model which is a raster way of depicting a surface,

and that's what we have here.

So, you can see there's the bottom of the valley here,

and then we go up the side of the slope here.

So, this is using a raster data model.

If I add in the contour lines,

this is a vector data model.

So, this is a different way of depicting the same terrain.

You're not going to get nearly as much detail,

it's not as rich of a dataset,

but depending on the purpose of your map,

that might be all that you want to put in there.

Typically, you wouldn't put both of them in at the same time,

I'm just doing this so you can compare the two.

So, for example, you can see there's this side valley up here,

and so you can see that the contour lines follow that.

So, you get a sense of how the lines are showing the terrain.

Here we have the 100-foot interval just the same as I was showing a minute ago,

and so again you can really see the detail that's visible

with the enhanced version or more lines that we have or the smaller interval.

This is a 3D perspective.

If I put this together with ArcScene,

if you're wondering how I made this.

So I draped the vector contours on top of the raster digital elevation model.

This is with a 200-meter interval,

and I just thought this would be useful to get a better visualization of

the steepness of the slope and how the contour lines follow those.

So you can see that there and there for example.

If I put in 100-foot interval as well just like I was doing before,

I'm hoping that this helps you to see or visualize,

for example there's this nice whatever you want to call it, peak-bump,

whatever, and you got the contour lines going up the side just as you would here.

At the bottom of the valley,

they're quite far apart because it's fairly flat and as it gets more steep,

the lines start to get closer and closer together.

There's really not a lot to work with with contour maps,

you can create contour maps from a digital elevation model in the software.

I'm not really going to go into the details of that here.

I just want you to know that these exist and that how to read them, how to look at them.

But one of the few things you can do is you can change the interval itself,

so that's how many lines there will be,

and then the width of those lines.

So here, the width is too thick.

This is not a very good map and then the problem is

once the line start to overlap each other like you're seeing here,

then you're reducing the legibility of those lines.

You're not able to tell them apart from one another,

and so you're losing information because you're not able to

actually discern those who're peak to no from one another.

This is a nice example of the government of Canada topographic map,

and I love the way they've put this together.

I've always admired their map design

in that there's a lot of information packed into these maps,

and you'll notice that these contour lines also known as

ISO lines or lines of equal value are there,

and if you want to see them,

if you want to pick them out,

they're easy to see if you need to see them,

but they don't dominate the map,

they're not overpowering the map.

If you're not interested in contours,

if you're more interested in the rail lines or the roads or whatever,

you can focus on those as well,

and that's the sign of a good reference map.

Just while I'm showing these topographic maps is a funny thing,

but this was purely by accident.

When I was putting it together, it's some Murphy's Law or something that of

course the area that I wanted to map was at the edge of two map sheets.

Not only that, one of them is using meters and one of them's using feet,

so they're using different contour intervals.

So, you've got these lines that

don't match or meet up at all at the edge of the map sheet.

Now, if I'm showing him out quickly and maybe nobody will notice,

but if you're actually needed to depend on this,

if you're out hiking or doing something like that,

this would be a bit of a problem.

So, this is unusual.

It's not something you'd run across all the time,

but I thought I would just mention it.