Lesson video

Hi, my name is Chloe, and I'm a Geography Field Studies tutor.

This lesson is called Sketch Maps and Cross Sections and it forms part of the geographical skills unit of work.

In this lesson we're going to be looking at what cross sections and sketch maps are and how we draw them.

Let's get started.

By the end of today's lesson, you'll be able to use sketch maps and cross sections to understand what a landscape is like.

There are some keywords to run through first of all.

A label, a written description of something in an image or on a map.

An annotation is a bit like a label, but it involves much more description and explanation of something that you might not be able to see in the image or on the map itself.

A cross section is an imaginary vertical slice through a landscape.

There are two parts to this lesson.

Firstly, how do geographers use sketch maps? And then how do geographers use cross sections? So let's start with that first one, all about sketch maps.

Now compare these two maps below of Brook Beach.

Which map appears to be more accurate? And which one tells you how local people think about Brook Beach? You can see on the left hand side of the screen we've got an OS Map, which is the more traditional style of mapping that I think we're used to.

And on the right hand side we have a sketch map and you might not have seen something quite like this before.

So which one do you think is more accurate? And which one do you think is more about people's personal opinion about a place? Well, if you look at the OS map, it's really, really accurate representation of what a place is like.

As far as possible, it's drawn to scale and it has all the main features of the place marked on it.

You can see it's pretty detailed.

Geographers may describe OS maps as objective.

They're based on fact.

Now, when you compare that to the sketch map, you can see it's nowhere near as accurate as the OS map.

Some of the detail has been missed out.

In fact, in this example, a lot of the detail has been missed out but as well as that other details have been included, so things that we didn't see on the OS map.

Sketch maps can give geographers information that would not traditionally be recorded by an OS map.

This one is drawn by a local resident and represents the things that are important to them.

So things like the fact that dogs are allowed on the beach, or there was a cliff collapse, maybe this affected their lives.

Geographers may describe sketch maps as more subjective.

They're more based on opinion than OS maps are.

A sketch map purposefully focuses on some elements of the map's location and not others.

And what elements are included depends on what the intended purpose or audience of the map is going to be.

So in this example, we can see we've got a section of London that you might have been to.

A map about tourism will show visitors a route that incorporates the best attractions.

Natural History Museum, the V & A Museum, Science Museum, the Prince Albert Memorial and so on.

So that sketch map has been drawn for a very specific purpose to guide people from one visitor attraction to another.

Other details on the map have been missed out.

Complete the sentences with the missing words.

Do pause the video and have a think about everything you've learned so far.

Come back to me and I'll tell you the right answers.

Right, let's see what answers you have.

A sketch map tends to be, something that means opinion based, subjective.

While an OS map tends to be more objective.

Sketch maps will include certain features and ignore others depending on the maps audience and purpose.

Sketch maps may not be completely accurate, but they still follow some of the conventions of more formal or traditional maps.

Sketch maps represent a location from above, a bird's eye view.

They may contain short labels or a key to show what features are, or how they're grouped, just like you would find on an OS map.

So here we've got a label dinosaur footprint.

So we're imagining it's going to be a fossil site and it's got a little symbol, it's got a label so we can see what's going on there.

You might find something very similar to that on an OS map.

A sketch map does not have to be aligned to grid north.

Remember our OS maps, the north point is always the top of the map.

Instead the map will normally be orientated in the direction that makes most sense for the purpose of the map.

Like an OS map, a sketch map should be drawn using clean lines.

Though it is subjective, it's not an artistic representation of a place.

That's an important thing to remember.

Sketch maps are often hand drawn, though they don't have to be.

You could do a digital sketch map as well.

This means that they're unlikely to be drawn to a scale.

Features may be shown as circles or blocks as you can see in the example here, rather than their actual shape 'cause they're trying to convey a message quite quickly rather than be drawn down into accuracy.

To improve the map's message, geographers may use written descriptions.

So let's look at our sketch map again.

It's now got a title.

"A sketch map of Brook Beach from a local resident's perspective." We've got this idea about the dogs being allowed on all year.

We've got the fact that we've got a great picnic spot, this fossil area with dinosaur footprints, cliff collapse, we've got something the Millie Road, it's called the military road in real life, but obviously locals call it something different.

A parking area, wooden steps.

Now some of those we would find on the OS map, most of that stuff we wouldn't.

Labels emphasise certain features and annotations highlight something that is not visible from the sketch map itself.

Sketch maps should also have a title, we've got one here, that highlight their purpose and from whose perspective the map is drawn.

And that's really important 'cause remember sketch maps are pretty much subjective so it's really important we know who is actually drawing that particular map.

Which of the written descriptions on this sketch map are annotations? Let's see what Izzy thinks.

"The description about the dogs is an annotation 'cause you can't see this on the map." You wouldn't know from looking at the map where the dogs were allowed on the beach or not.

"The picnic area might be marked on the map, but I wouldn't know it was a good spot without seeing this annotation." So we've got somebody's opinion that that's a really great picnic spot.

That's something that is subjective.

You wouldn't find that on the map itself.

"The map wouldn't show when the cliff collapsed took place either." So it might show that there might be a change in landscape shape, but you wouldn't know when that had occurred.

So lots of elements of a sketch map actually are annotations 'cause they tell us things that you cannot see directly.

Let's check our understanding of that.

True or false.

A sketch map should look like an artistic sketch of a location.

Is that true or false? Have a think.

Pause the video and then come back to me.

Okay, hopefully you have remembered that that is false, but why is it false? Well, despite its name, a sketch map should be made up of clean lines to clearly show the different features of the map.

It's important we can still read the map and understand its purpose.

Our first task of this lesson.

Study this example of a sketch map.

List all the features that make it different to an OS map.

So you can see here we've got maybe some playing fields I think we are looking at.

So we've got a football pitch, car park, woodland, some trees, playground and so on.

We've also got a title, "A sketch map of Middleton Park from a local child's perspective." So that's quite an important addition there.

So list all the features that make it different to an OS map.

Think about all the things we've just learned.

Pause the video and write me a list of those features.

So let's look at what you've got.

Your answer could include these points.

The features are not drawn to scale.

You can see there's no scale bar on the sketch map.

The features are probably not their accurate shape.

You can see they're a little bit random.

They're not drawn with any accuracy.

The map is not north aligned.

Hopefully you notice that.

And of course, remember our OS maps are always north aligned.

Some features are not included.

There's going to be things there in that playing field, in that woodland, which are important but which are not included.

We don't know for example what type of woodland it is and that would be included on an OS map.

Local information is included instead.

Things like the fact that the football pitch gets really muddy in winter, that wouldn't be something that you would read on an OS map.

And the map has annotations as well as labels, so we're seeing that level of subjectivity coming into the sketch map that we wouldn't see on the OS map.

Hopefully, you've got those points.

So the second part of our lesson, how do geographers use cross sections? Now a cross section is a graphical representation that appears to show the landscape as if it were cut through.

It's almost always a cut along an axis with the ground at the bottom and the sky at the top.

So it's like you're slicing through the atmosphere through to the earth.

For example, a river channel will be cut from bank to bank.

And you can see in the photo there, X on one side and Y on the other.

That is a very traditional way of marking your start and endpoint of your cross section.

And then you can see in the sketch of the cross section there, you've got X and Y and you can see that you've got the river channel there underneath it.

A cross section might be used to show the depth of something, such as a beach, or the relative height of something, such as a building in a skyline.

Geographers might use cross sections to show what is not immediately visible such as soil or geology or how the gradient might change along a route.

The cross section's title will always tell the geographer what it intends to show.

So here we can see we've got a soil profile.

In other words the depth of different layers, different areas of soil sit at, a cross section of the downland to show the soil profile of the area.

It looks like earth has been kind of sliced through.

Map cross sections are drawn accurately to scale.

These are line graphs with a horizontal distance along the X axis and a vertical distance, or depth, or height along the Y axis.

So these are very specific.

A map cross section will look like a line graph.

Other forms of cross section will look more like a kind of graphic for how the earth has been kind of cut into.

But a map cross section is very specific.

It will look like this, nothing like a map really.

This cross section shows the change in elevation between two points on the map.

So again, X and Y marking the start and the finish goes up very steeply to around 50 metres above sea level, and then drops gently down towards our Y marker.

Map cross sections might also be labelled and annotated with additional graphical information like a sketch map would be.

So you can see on our example here, we've then got a section of woodland has been identified and that's been added to our map cross section.

Map cross sections may be used to measure aspects of the landscape.

Geographers can find out the highest and lowest elevations in the cross section.

They could literally read these off the graph.

The total width of the cross section, again, you can read that from the graph.

How land use or cover changes with elevation.

If there are any unusual features such as a height or depth that appears out of place, a kind of anomaly within the landscape.

And how the gradient changes.

So we can actually use those map cross sections to find out an awful lot about what the landscape is like.

Let's check our understanding there.

Which of the following would you not expect to see on a map cross section? Is it a scaled axes.

Key, a title, labels or annotations? Which one would you not expect to see? Pause the video and have a think and then come back to me.

Hopefully, you've realised that the thing you would not have on a map cross section is a key.

Yeah, so we do have axes.

They're most often scaled, sometimes they're not, but they would be almost all cases have some kind of scale on them.

Your map cross section would definitely have a title to tell you what its purpose is.

And it would have labels and annotations to highlight certain features of the landscape.

So how would you actually draw a cross section? First of all, on your map you would mark the X and Y points, X being the start and Y being the endpoint of your cross section.

You would then take a piece of paper and you'd have to make sure this piece of paper is long enough to mark both the X and Y points on it.

You would lay it out so it's straight edge is between your X and Y.

Then with a pencil, you'd mark that start and endpoint, the X and the Y, and then you would mark every position of every contour and label its height.

So you can see here just a little marker's been placed onto the paper for the 10, 20, 30, 20 and 10 contour lines.

You'd also make a note of any features that you might want to label or annotate on your cross section.

So in this case, we can see that between the 10 metre contour and the endpoint Y, we've got a marsh.

So that's quite important thing.

So this person has actually written that on there piece of paper.

You'd then take a piece of graph paper and you draw a pair of axis, a traditional X and Y axis.

The maximum Y value would have to be the top of your Y axis.

This is to ensure that we can actually fit all of your cross section onto the paper.

Then you'd place your piece of paper along the X axis and mark the contour values at the corresponding places on the graph.

You can see on the piece of paper where the 10 contour line marker has been put, that person has then gone up to the 10 metre point on their Y axis and place little cross.

They've done the same for the 20, the 30 and so on.

You would then join the points together and it's really important you don't use an angular line.

You don't go straight from one point to another.

You try to use a nice, gentle curve between the lines, trying to as closely as possible represent the landscape that is on your map.

You would also add any labels that are needed.

So the marsh has been added in here between that 10 metre point and the end of the cross section at Y.

You complete the graph by drawing a second Y axis that is kind of neatly framing the entire thing and you would write a title as well.

So in this case we can see, "A cross section to show the change in gradient between point X and Y." So let's check our understanding of that process.

Andeep has drawn a cross section of a valley, but what mistake has he made? So we've got a title, we've got the points are in there, we've got a label as well.

Let's see what our options are.

He's not drawn enough points to make it accurate.

He has used sharp angles to join the points.

He has drawn two Y axes or he has added a label.

Have a good look at the graph that Andeep has drawn.

Pause the video and then tell me what mistake has he made? Okay, hopefully you can see that the mistake that Andeep's made is that he's used these kind of sharp angles.

He's gone directly point to point rather than having a nice curve to his line.

Your second and final task of today.

Practise drawing a map cross section using the contour map below and some graph paper.

Remember to include any necessary labels and a title.

I can see one thing on this map that you're probably gonna want to label.

For this task, you do not need to use the correct scale on the X axis.

You can see this map has not been given a scale so you don't have to try and use one.

This is gonna take a little bit of time.

Do go back over the steps if you need to, to remind yourself of how to do this.

Pause the video and then I'll see how your graph compares with mine.

Okay, let's look at your graph first of all.

So you should have something that looks a little bit like this.

You should have a fairly gentle slope.

You should then have a lake that that's labelled and then have a quite a steep slope going up towards the 90 metres.

There's other things you need to make sure that you have done, so check these off with your own copy.

Check that you have put two Y axis onto your graph.

One on the left and one on the right.

You should also have a title on your.

Sorry, your Y axis.

So you can see I've labelled up, "Metres above sea level." So it's really clear what this elevation is being measured in.

You should also have a main title for the whole cross section.

So here, my title has been, "A cross section to show the change in elevation between points X and Y on the map." You'll probably have something similar.

I hope you spotted that there was a lake that you should have labelled on your map as well, so that's been labelled.

I've actually changed my colour as well to show that there's water there.

And you can have a gentle curved line.

Remember, no angles between the points, has to be a nice gentle curve between those different points.

Hope you manage to get all of those correct.

Let's review what we've learned today.

A sketch map is a map drawn for a specific purpose that may miss out some of the detail of an OS map.

A sketch map helps us to understand how someone might view a landscape and what is important to them.

A cross section is a graph of a landscape as if it has been sliced open.

It is used to show the depth or height of something as well as gradient.

Well done.

Being able to draw a sketch map and a cross section are two really important skills for you to have in geography.

Best now to actually go away and practise them for yourselves.

Maybe draw a sketch map of somewhere that you know really well, or choose an area of an OS map that you are unfamiliar with and then try to draw a map cross section from it.