Lesson video

Hello, my name is Chloe and I'm a geography field studies tutor.

This lesson is called Using and Interpreting Spatial Data, and it forms part of the geographical skills unit of work.

We're going to be looking at what spatial data is and how we can use maps to really showcase it.

Let's get going.

By the end of this lesson, you will be able to interpret spatial data that is shown in a variety of map styles.

Before we begin, there's some keywords we need to review.

First of all, spatial data itself.

This is data that is assigned to a specific location.

You might have heard of GIS before.

It stands for Geographical Information System.

It's software that creates maps of spatial data as well as having digital tools that you can use to analyse it.

Choropleth shading is where we use density of colour on a map to show the density of data spatially.

An isoline is a line on a map that joins points that have the same value.

This lesson is in three parts.

First question we're going to ask is what is spatial data? We're then going to ask how does GIS help geographers understand data? Finally, we're going to be thinking how about how can spatial data be displayed on maps? Let's start with that first one.

Spatial data is data that is specific to a particular space or place.

Geographers specialise in handling spatial data.

This is what makes them distinctive from scientists and sociologists.

An ecologist for example, might study the relationship between plants and animals, but a geographer might also be interested in those things.

What makes a geographer different is that they will want to understand how space and place through the collection of spatial data, has an influence on that relationship.

So most data that geographers handle is spatial to some degree because it's all happened in a particular location.

To make data specifically spatial, it must have a spatial marker.

This is an element of data that tells geographers where it was collected.

So spatial markers might include things like latitude and longitude points.

It might be a geo GPS coordinate, it might be a grid reference, a postcode, or it could just be a location name.

All of those things are spatial markers that can be attached to the data to tell the geographer where it took place.

Let's check our understanding of those ideas so far.

Complete the sentences with the missing words.

Do pause the video and have a look at the paragraph below and then come back to me with your ideas for what can go in the blanks.

Okay, let's see what ideas you had.

Geographers specialise in handling spatial data.

When they study something, they want to know what influence space and place have had on the data.

The data has to have a marker, such as a latitude and longitude, a GPS coordinate, a grid reference, a postcode or a location name.

Well done if you've got those.

A Geographical Information System or GIS is a way of digitally mapping spatial data.

It is computer software that takes the spatial markers that have been paired with the data and uses these to place the data at the right point on a map.

So those postcodes or those location names, GPS coordinates, latitudes and longitudes and so on, it uses that data to then put that data onto a digital map.

This then allows geographers to see if there are any spatial patterns in the data or they could use the data to describe the characteristics of a particular place.

Using GIS is not the same as drawing the data by hand on a paper map, something you've probably already had a go at.

Not only is GIS quicker and it's gonna be more accurate because it's using digital spatial markers, it also allows a greater depth of meaning to be gained in the interpretation.

GIS allows layers of data to be viewed through each other.

This means that spatial relationships between data sets can be found.

We're gonna talk a little bit more about this later in the lesson.

Data can be edited, it can be added to, it can be filtered and you can't do any of those things if you are using data that has been presented on a paper map.

Right, let's check our understanding.

Using a GIS map is no different to using a paper map.

What do you think, is that true or false? Pause the video and then come back to me.

Well done if you recognise that it is false, why is that statement a false one? Yes, so plotting data on a GIS map is more accurate and allows for greater levels of data manipulation and interpretation.

Our first practise task of this lesson, place ticks in the correct places in the table to indicate the most suitable spatial markers for the data given.

So you can see you've got four different types of data, which could be presented on a map, and you've also got four different spatial markers, latitude, longitude, a grid reference, postcode, or a location name.

Now it's worth noting here, some of the data may work with more than one spatial marker, so don't worry if you're going to have more than one tick per row.

Pause the video here and have a really good think about which type of spatial marker is gonna be paired most effectively with what type of data.

Let's look at where you've placed your ticks in the table then, let's start off with that first one.

Cities that receive high levels of in-migration, thinking about the kind of spatial marker that would work best with this.

Well done if you recognise location name, that would definitely work, but well done even more so if you recognise that latitude and longitude could be used.

That would work perfectly if we're looking at a world map and we're trying to pinpoint cities.

Now we're going to go more detailed here.

So now we're looking at road junctions that have high levels of air pollution.

Well, we can see that some of these instantly aren't going to work.

A road junction doesn't have a postcode or a location name for example, but a grid reference would work really well.

It would really pinpoint where that is on a map.

Latitude and longitude, no, it would be too big.

Next one, streets with a higher proportion of people who are aged over 65.

Ah, so now we're looking at streets.

Now streets do have a postcode and they also have a location name.

Problem with the street is that it's going to take up multiple grid references, so that probably isn't going to work as well.

And likewise, latitude and longitude, again, way too large a space could be considered for that.

So streets aren't going to work alongside latitudes and longitudes.

Our final one, areas of a country that have seen the highest levels of deforestation.

Right, now here we're going in the opposite direction.

So if it's an area of a country, it's unlikely to have a location name 'cause it could cover lots of different areas and quite large areas maybe that cover lots of different place names.

Definitely not a postcode, but yes, grid reverences would work and latitude and longitude would work as well.

Hope you got those in the right place.

Our next part of the lesson is gonna answer the question, how does GIS help geographers understand data? To read a GIS map, one needs to understand how such maps are structured, if you like, how they're drawn.

The starting point of a digital map is the base map.

This is the map onto which all the data will be secured.

You want to think of it, if you like, as the bottom layer of all of the map.

There's lots of different base maps that can exist and they all have slightly different purposes.

So some base maps may show physical features such as relief, you can see on our base map here, we've got the waterways are marked and we've got contour lines.

These would be used when the final map's data is connected to the physical environment.

So if we are presenting data, which is purely physical geographical data, probably gonna be using a base map, something like this.

Now instead you might have a quite different style of base map.

It might show human features such as roads, and these are going to be used when the final map's data requires a link to more human spaces.

So you can see in this example here, some of those other physical features don't exist.

We haven't got waterways, we haven't got relief markers, for example, we have got a little bit of land use indicated perhaps by the green spaces and then the buildings, but the road names and their shape and size is going to be more important for the type of data that is presented on this type of map.

Spatial data on GIS maps is held on layers.

It's quite difficult to understand this, but it's best to think of them a little bit like digital pieces of tracing paper that get laid over the top of the base map.

One layer or one piece of digital tracing paper will hold the data from one data set.

So multiple layers can be laid on top of the base map and on top of each other.

So you have your base map at the bottom and then you have your layers of data on top.

This means that someone reading a GIS map can see the base layer and multiple layers of data all at once.

They can see right through from the top layer of data through to the base map.

Again, think of it like tracing paper.

This helps them to see spatial relationships between the data sets, so they can see how one layer of data might have a relationship to another layer of data and might have another relationship to the base map itself.

Let's check our understanding here.

Sam wants to compare house prices with their age and their distance from a river.

What is her most likely GIS setups? Let's look at that again, house prices, the age of the house and where the house is in relation to a local river.

Is she going to use a base map, a layer of house prices, a layer of house ages and a layer showing the river's position? Is she going to use a base map showing physical features, a layer of house prices and then another layer of house ages? Is she going to instead have a base map showing the physical features, a layer of house prices and house ages together on one layer? Which one is her most likely GIS setup? Have a think about those digital pieces of tracing paper and how we use a base map.

Pause the video and then come back to me with the right answer.

Well, hopefully you can see that it's answer B.

So her base map is going to show all the physical features, she's then gonna have a layer showing the house prices and a layer of the house ages.

She's got everything covered there.

She doesn't have to have a separate layer showing the river itself.

That would be on her base map.

Spatial data can be presented in one of three ways.

Again, we're thinking about how it is that these maps are produced.

You could have a point.

So data is assigned to a single point on the earth's surface.

So something like our latitude, longitude point, that is a single point on the earth's surface.

It cannot be disputed with anywhere else.

You might have your data as a line, so the data is shown as a flow from one point to another.

Something like the movement of a river or traffic on a road would be line data.

You might also have polygons.

So this is an area that's assigned to data where the whole shape has the same identity.

So you might have a lake or a piece of woodland, something like that where it's an area rather than a point or rather than a line.

Now point data could include specific points where an event has occurred or data about specific spatial features such as trees or mountain peaks.

In the example we've got here, we've got data where a particular event has occurred, in this case, it's an earthquake in the year 2017.

So each point on that digital map is a point of an earthquake.

It's where the epicentre of the earthquake took place.

Line data could include flows of money, such as overseas investments.

It could be water such as rivers, people, migration roots or soil like landslides.

So anything which is showing movement between two points can be shown as line data.

In the example we've got here, again, we are in the hazards topic and we are looking at tropical storms and the paths that they take coming off the sea and making landfall.

Polygon data could include land use such as blocks of retail or housing or land designation.

So something where somebody has actually given the land a particular title, such as a Site of Special Scientific Interest, or an AONB, an area of outstanding natural beauty.

Those types of designations would also count as polygon style data.

In the example here, we've got the index of multiple deprivation and it's showing how different areas compare with each other in terms of deprivation data.

It could also show other values where the land has been split into separate areas, such as values assigned to different countries or to regions.

So if there are natural kind of like borders in the land, like state borders or country borders, you might use polygon data there to show the difference between different countries.

Let's check our understanding.

True or false, traffic levels passing through an area could be shown as line data on a GIS map.

What do you think, true or false? Pause video and I'll tell you the right answer in a moment.

Well done if you recognise that it's true, but why is that statement true? Yes, it's all because traffic flows can be shown as a line because we are looking at where traffic starts, where it ends, and therefore it's going to be a movement between two points, well done.

Now our practise task here, we've got a mix and match task, match the data to the way it would be presented on a GIS map.

The three that we've already covered, point data, line data, polygon data.

You've got three different types of data as well.

Which one would you present in which way if you were designing a GIS map? Pause the video and see if you can work it out.

Okay, let's look at your answers.

So first of all, stream flow rates as they pass through a drainage basin, we are moving from one point to another.

It can only be line data.

Different types of woodland found in a national park.

It's going to be areas of land, so it's got to be polygons.

And eruption magnitude data for a number of volcanoes, and a volcano is at a particular point on the earth surface, so it has to be point data.

We're coming onto the final part of today's lesson.

How can spatial data be displayed on maps? Presenting spatial data can use some sophisticated mapping techniques.

We've got an example here, a dot map.

This shows many locations of point data.

In this case, the data points do not have a value, but instead each dot is simply a point to show an observation of a certain feature.

So every time you see a dot in this example, you know that's where an earthquake has taken place.

There's no other value assigned to that particular dot.

Interpretation of dot maps involves geographers looking to see where there are areas of least and most dots clustered.

Now classically on something like an earthquake map, we can see that the earthquakes are clustered around the plate boundary lines.

This tells them where there is the greatest density of something and also of course, where there's the least density of something.

Point data that has values can be shown as proportional symbols.

You will have seen a map like this before, I'm sure.

This is where the larger the symbol, the larger the measure, the count, the score or the rank of the data.

In our example here, each point is a world city, but the size of that point has been shown as the size of the population of that city.

So the larger the circle, the larger the population of the city.

Geographers interpret these maps by seeing if there are areas of large symbols all in one place.

They might also look for patterns where the symbols progressively get larger or smaller as they go across an area or along a route or along a transect.

So for example, if you're looking at cities, you might look, is there a particular part of the world that seems to be having more large cities than others? If it was different type of data, you might think why is it going from smallest to largest size circle in a particular place or along a transect? If point data might occur in spatial bands or clusters, an isoline map may be used.

An isoline joins points together of the same value.

If shading is seen between the lines, it is known as an isoplath map.

Now it's really important here to get your head around the fact that this is still point data, even though you can't see individual dots on the map.

They've been joined together by lines, but it's not line data, it's still point data.

In this example, an isoline map has been used to show the maximum summer temperatures in 2018.

So any point on that line which is labelled as 22 degrees Celsius, we know that that place has a point on it which has a value of 22 degrees.

Geographers will look for areas of rapid change in value.

So where the lines are close together, it means that in this example, we are going from one temperature very quickly across the land to another temperature.

You would also look for areas where there's no change in value, so where the lines are much, much further apart, and this would tell us that there's pretty uniform temperatures in that part of the UK.

Let's check our understanding of that.

What is the difference between a dot map and an isoline map? Is it A, a dot map has no values, the dots just show the location of something, B, a dot map has the points joined together, C, a dot map has symbols that are sized according to their value or D, a dot map will show progressively larger or smaller symbols.

This is not easy 'cause all of those sound quite familiar from what we've just learned.

So read the descriptions carefully, pause the video and see if you can find the right answer.

Right, let's see what you got.

Well done if you recognise it was that first description, a dot map has no values.

The dot is just showing where something took place, so where there was an earthquake, where there was a volcano, where there was a pine tree or something like that.

It doesn't show any other value associated with it.

Where the point data is quite complex, a situated chart map may be drawn.

We've got an example here, a situated bar chart map to show traffic data for three areas of Ventnor.

So we've got three small bar charts drawn onto the map to show how the traffic data are varied, both in the total amount and according to different types of vehicles.

Small charts, such as pie charts or bar charts, are placed on the point on the map where the data applies.

That's quite important, so it can show that spatial relationship as well.

Geographers interpret these maps by analysing the data in the small charts before thinking about their relative position on the map.

So they look at what are the charts telling us and then they think about how the charts relate to each other spatially.

Geographers may use flow line or desire line maps to show the movement of things from one location to another.

Here we've got a desire line map to show significant migration routes from Singapore.

So where people from Singapore might be migrating to, and you can see pretty much all over the world by the looks of things.

The lines may be shown as arrows to show the direction of movement and it could be that you have the wider the arrow or the wider the line, the larger the flow.

Flow lines on maps show exact paths taken, while desire line maps will show flows as straight or curved lines.

So in the example here you can see it's a desire line map, it's not showing the exact route that somebody takes from, for example, Singapore to get to Australia, it's showing the more direct route or curved route, kind of indicating like the path of a flight, for example.

Geographers interpret flow line maps and desire line maps by looking carefully at the point of origin and the point of termination of different lines, so where it starts and where it finishes.

They will also examine the thickness of the lines or the arrows to see if certain types of places have the greater or lesser amounts of flow.

So if all of the thick arrows are going all in one direction and all the thin arrows going in another direction, that instantly tells geographers that there's a pattern to be had.

Choropleth are used with polygon data.

They show a particular type of colour system.

So choropleth shading is where one basic colour is used, but darker and lighter shades of it show the different value of that polygon.

And generally it's the case that on the scale, the darker the shade of that colour, the higher the value of the data in that polygon.

Let's look at our example here.

We've got polygons and naturally because we're using country borders, so we've got blocks of colour across the map, it's showing maternal mortality rates per 100,000 live births.

So the darker the colour, the more mothers that are dying in childbirth, the lighter the colour, the fewer are.

Do also note here the spelling of choropleth.

It is a very common misspelt word.

It does not have an L at the start.

It's C-H-O-R, choropleth.

Geographers interpret choropleth maps by looking for areas dominated by extremes of dark and light shades.

They'll also look for patterns where the shading gets progressively darker or lighter across a route or across a transect or across a country.

For example, in this map, we can see quite easily the areas where there is the greatest amount of rainfall.

It's the areas that have been shaded the darkest.

We also can see the areas where there's the lowest levels of January rainfall, more towards the east of the country.

But if we look here, if we were to travel from west to east across the UK, we can definitely say that it goes from wet to dry.

It's a very clear pattern that we can interpret from the choropleth shading.

Let's check our understanding.

Complete the sentences with the missing words.

Have a look at the paragraph and see if you can find the words that need to fill in the blanks.

Do pause the video and I'll come back to you.

Right, let's see what answers you got.

Flow line or desire line maps can show line data, while choropleth maps show polygon data.

To interpret flow line maps, geographers study how thick the lines are.

Interpreting choropleth maps means studying how dark or light the shade of the areas shown are.

Hope you got those.

Our final task of today's lesson, study this choropleth map.

You can see it's of London.

It shows the population density of the different boroughs of London and the surrounding areas.

You've got a key underneath to help you as well.

Use the map and the key to describe the pattern of population density shown in the map.

You are probably going to be looking at about three or four sentences to make your description.

Do pause the video, have a really close look at the map 'cause there might be some data there that would surprise you.

Here's some of the things you could have included in your answer.

The centre of London generally has the highest population density, and I've actually quoted some data there.

An exception is one small borough right in the centre of the city where the population data is between 1,213 and 3,121 persons per square kilometre.

As one moves away from the centre of London, the population density decreases.

So I've used the choropleth shading to make three clear comments about this particular example.

Let's summarise our learning for today.

Geographers specialise in handling spatial data.

This is data that is linked to space and place.

GIS maps help geographers define spatial patterns in the data using point, line and polygon data.

Maps showing spatial data include dot maps, proportional symbol maps, isoline maps, situated chart maps, flow and desire, line maps and choropleth maps.

Interpreting these involves looking at the data itself as well as spatial patterns between data features.

Well done, there was a lot to take in there, wasn't there? Now the best way to really get to grips with different types of spatial data and GIS maps is to really have a good look at them for yourself.

See if you can find any examples online or in any textbooks that you have.

And you can see how geographers have used those mapping techniques to present different types of spatial data.