Advanced Higher Geography

Maps & Diagrams

It often makes sense, in Geography, to present information on a map. This can range from a simple map in an atlas up to extensive geographical information systems, which allow data to be stored, analysed and presented on much more complex digital maps.

We will cover a range of different styles of maps and diagrams:

Sketch Maps
Isoline Maps

Dot Maps
Choropleth Maps

Proportional Symbols Maps
Flow Line Maps

Sphere of Influence Maps
Transects & Cross Sections

Annotations

Annotation means to add notes to photographs, overlays, field sketches, graphs, maps, diagrams or data tables. The purpose is to highlight relevant information to the reader.

For example, a sketch map created using an overlay could include annotations which focus the reader on relevant features, such as roads, in a transport study.

The annotations can be added by hand or digitally.

Sometimes an annotated photograph isn't as valuable as a field sketch. In the same way, an annotated map may be superseded by a sketch map. These further draw the reader's attention to the relevant information and remove all the "noise" from the background.

Useful when:

There are clear features to be identified - not too many and not too few.
The annotations, sketch maps or field sketches contribute to the reader's understanding of the written information. That means they're not necessary for very simple things (e.g. I saw a cliff) and that they may not be very appropriate for very complicated things.
Linked to written text.
They are carefully planned - what information will you include and highlight - and what information are you removing as it's not relevant?
The position of the annotations don't make things too busy or overlapping.

Question: What are the main features required in a field sketch?

Watch this video from GeoBus and include a list in your notes.

Worked example

Starting at the top of the diagram and working down the page, we can see that the input into the drainage basin is precipitation. Most of the precipitation falls onto the vegetation and from there some of it is lost through evapotranspiration. Of the remainder, the water flows from the vegetation down into surface depressions where again some is lost through evapotranspiration and some becomes overland flow into channel storage.

The rest infiltrates into the soil to become soil moisture and again some is lost through evapotranspiration and some becomes throughflow into channel storage. Some of the soil moisture then percolates deep into the rocks to become groundwater which flows into channel storage.

Imagine having to read the above paragraph without the data being presented graphically. It would be mind boggling! This demonstrates a good use of a systems diagram.

By using the same terms as the diagram, and putting them in bold, it's easy to refer between the diagram and text.

Activity

This text talks about the inputs, stores, outputs and transfers involved in the glacial system. Using the terms in the text, create a systems diagram.

The glacial system consists of inputs, stores, transfers and outputs. Understanding the connections and relationships between the different components of the system helps indicate how a change in one component results in consequential changes throughout the system.

Inputs - The main input to the glacier system is through precipitation in the form of snow. Ice and snow can also be inputted to the glacial system through avalanches which can occur both naturally and due to human activity in mountain areas. Inputs to a glacier result in accumulation.

Stores - The mass of ice within a glacier is a store that can be added to (accumulation) or lost (ablation). Material that is carried by the glacier is also known as a store.

Transfer - The transfer is the movement of a glacier due to gravity, gradient and increasing accumulation at the glacier source. In mountainous areas this movement is much quicker than that of ice sheets, which are often on a flatter surface. The main movement is downhill although, unlike water, ice has the capacity to move uphill if the ice pressure behind is great enough, resulting in the over-deepening of glaciated valleys.

Outputs - The main output is the loss of water vapour from the evaporation of water from the glacier’s surface. If, under certain circumstances, snow and ice converts directly to water vapour without going through the liquid water stage it is known as sublimation.

Another output is calving which is where blocks of ice break off at a glacier’s snout. Usually this occurs where glaciers end in lakes or the sea, but it can also occur when ice falls off the end of a hanging valley glacier.

The other main water output from a glacier is where water leaves the snout of the glacier in liquid form as meltwater streams.

All these outputs from a glacier’s ice store are known as ablation. Solid material leaving the glacier can also be included as an output. As a glacier retreats (melts towards its source), rocky material will be washed out of the glacier, known as moraine.

Choropleth Maps

Choropleth maps show data across different unit areas.

The unit area will depend on the scale of the map - it could be a whole country or a smaller region.

Useful when:

Data is assigned to different regions/areas.
You are identifying patterns across a town, region or country (e.g. most of the areas in the south have lower poverty).
The data is ordinal, interval or ratio.
Colours chosen are appropriate; often this means graduated shades of one colour, but in some cases (e.g. temperature or things that are both positive and negative) these can be a range of e.g. red to blue. Pick colours appropriately - don't use red when talking about ice coverage and brown when looking at areas that have been reforested.

Question: Which of these sets of data would best be presented as on a choropleth map?

A – Changes in life expectancy (increase or decrease) across the US state of Alaska since 2020.

B - The reasons that people have chosen to live in a new housing development.

C - The angle of slopes across a raised beach.

The correct answer is A. If the data given is based on regions or areas, a choropleth map would visually show patterns of increase or decrease and allow trends to be identified. This could be useful data to those working on improving health outcomes or access in Alaska.

The data in B would give qualitative data, which is rarely used with choropleth maps. C would be best represented using an isoline map, which we will come to later in your course.

Worked example

The decision about how to group or categorise your data is often the hardest. In this population density map of Nepal, there are enough groups that it is useful data, but not too many that it becomes complicated.

The map makers have made the decision to have uneven groupings, i.e.:

Most of the groups have a range of 100
One of the groups has a range of 700
They have chosen to include a "above..." and "less than..." category

Ideally, choropleth maps should have categories with equal ranges, but sometimes map makers make deliberate decisions, based on the data they're working with, to do otherwise. Common groupings include:

All groups having the same range
All groups increasing in range evenly
Standard deviations
Natural breaks
Equal number of values/regions in each group

The darkest colour is usually used for the highest; in this case the capital city of Kathmandu stands out as having a very high population density.

Activity

Nitrous Dioxide (NO₂) is a gas, formed during combustion, which is the major contributor to air pollution in cities. It is a respiratory irritant, which worsens asthma and can contribute to infections in the lungs. It also contributes to smog and acid rain.

Some cities around the world have implemented low emissions zones (LEZ) to reduce the impact of air pollution. One of the cities which has done this is Glasgow.

As part of the work done to plan the LEZ, areas across Glasgow had their NO₂ levels measured.

Collect a print out of the map of Glasgow and create a choropleth map of the data. You will have to decide on the groupings/key and pick an appropriate colour scheme.

Proportional Symbols Maps

These display data using symbols or pictures which are different sizes. For example, a circle may appear bigger if the data value is larger.

There are two kinds:

Absolute scaling - where the symbols are mathematically proportional. e.g. a circle representing 2 million people is twice the area of a circle representing 1 million people.
Range grading - where each size of circle is assigned to a value/range of values, like in a choropleth map.

Useful when:

Data is point data - it can be tied to a specific place.
The symbols are far enough apart that they are all readable. This could be done by choosing an appropriate scale or not including small values.
Geometric shapes (circle, square, star) can be used, but thematic pictorial symbols can also be used to match the theme of the map. For example, a map of airport departures might use scaled plane pictures and a map of population might use stick figures.
Transparent symbols (as in the proportional-squares map) can be used, but too much overlap can cause difficulties with interpreting data.

Look through an atlas and find 5 examples of proportional symbols maps. What kind of data is displayed in this way?

Worked example

This is an example of an aggregated scale map, where the symbols are truly proportional. Only countries with urban populations more than 1 million are included, which removes the problem of overlapping symbols. Additionally, colour has been used to denote different continents.

The key is useful and includes some examples of circle size so that rough estimates can be easily made. There are some places (e.g. south-eastern Europe and central America) where the scale of the map makes it difficult to see the populations.

As the data is averaged across the whole country, the central point of each country has been used.

Activity

The emissions of NO₂ were measured again a year after the introduction of the LEZ. This was done using diffusion tubes, a low-cost way to sample pollutants over a 4 week period. The tubes are then analysed at a lab to determine the levels of NO₂

The LEZ was enforced from 1 June 2023.

Glasgow LEZ map

The results from after the introduction of the LEZ are shown in the table below. Draw a proportional symbols map of the results and answer the questions.

You will need to decide whether to use absolute scaling or range grading.

1) Glasgow's LEZ lies entirely within the Anderston/City ward of the map. By what percentage have the emissions here decreased?

2) Many of the other wards have also seen their NO2 levels decrease. Suggest two reasons that this might be.

3) Calton (Ward 9) has not seen a decrease in NO2 levels. Referring to the map, suggest why this might be.

4) The Glasgow LEZ was introduced with the aim of reducing air pollution in the city centre. What other social, economic or environmental benefits come from the introduction of LEZs?

4) Compare the choropleth and proportional symbols maps you have produced. Which technique works best to display this data? Give two reasons why.

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