A-Z of cartography

Read our hints and tips to guide you through the world of cartography with this handy A-Z from our GeoDataViz team.


A – Analysis

Geographic data can be used to perform geographical analysis. This is often performed using Geographic Information Software (GIS) and can be used to help you perform map-based analysis, answering and addressing numerous questions about your data. 

B - Boundaries

Boundaries on a map are normally used to represent the division between one entity or political unit from another, and are usually represented by a line. Boundaries are a good source for creating thematic maps which generally focus on a particular theme connected with a geographical area.

C - Colour

Colour plays an important part in helping aid the communication of a maps layers. It can be used to help provide familiarity between the real world and its representation on a map and can make the important elements of your map stand out. The OS GDV toolkit offers some useful guidance.

D - Data

Geographic data is information describing the location and attributes of real world things including their shapes and representation. This data comes in a range of formats and can be used to make maps, solve problems, provide insights and more.

E - Elevation

Elevation is the distance above sea level and is most commonly depicted through a topographical map. It is usually measured in metres or feet and can be shown by contour lines, bands of colour or by numbers giving the exact elevation.

F - Fonts

The right font choice is an important part of the map design process. With so many to choose from, it is easy to get it wrong so try to keep it simple. Don’t clutter your map with a range of different fonts and only use fonts that are still legible at smaller sizes.


A geographic information system is used for capturing, storing, analysing and displaying spatial or geographic data. It can be used to link seemingly unrelated data, helping you better understand spatial patterns and relationships.

H – Hierarchy

H is for hierarchy. A hierarchy is used to draw attention to certain elements of a map and push those of less importance further down the visual plane. This helps you differentiate map features and understand the map’s message effectively.

I - Icons

A map icon is used to represent and locate real objects and without them, a map might be quite difficult to understand. You can use icons to represent point, line or polygon features and they should ideally be as easily recognisable to your audience as possible.

J - John Snow

Not just a Game of Thrones character, John Snow was an English physician in the 19th century. His cholera map is often cited as one of the earliest known examples of geographic analysis being used to understand a health epidemic. His use of mapping in epidemiology is now used in GIS textbooks and courses to highlight the application of geographic analysis.

K - Knowledge

Geographic data can be used to inform and improve decision making. Data can be processed and visualised so that it turns into information and, ultimately, into knowledge.

L - Legend

A map legend is used to help explain the meaning of symbols on a map and it gives you the information needed for the map to make sense. Symbols in the legend should be shown in the same size, colour and depiction as they are on the map.

M - Marginalia

Most maps have two basic parts; the map itself and the information about the map. This information is commonly referred to as marginalia as it sits outside the edge of the map within its margins. Map marginalia can include titles, north arrow, copyright notice, legend, scale bars and publication date.

N - North Arrow

A north arrow is used on maps to indicate which direction north is. While it is not always necessary to show a north arrow, it can be useful in case your intended audience does not understand the orientation of the geographic area shown.

O - Ordnance Survey

Founded in 1791, Ordnance Survey is Great Britain’s national mapping agency. It carries out the official surveying of Great Britain, providing the most accurate and up-to-date geographic data relied on by government, business and individuals.

P - Projections

A map projection is a way of visually transforming the 3D earth onto a flat sheet of paper or computer screen. All map projections distort the earth’s surface in some way, and different projections are chosen depending on the purpose of the map.

Q - Quality Control

Quality control is an important part of any map design process and is used to ensure a map is error free and meets the user requirements. Cartographers pride themselves on being able to accurately visualise the real world and QC helps make sure they achieve this.

R - Raster (and vector)

Geographic data generally comes in two forms: raster or vector. Raster data is an image made from a grid of pixels (think satellite imagery) whereas vector data can be points, lines or polygons made up of paths and vertices (e.g. a road network).

S - Scale

Map scale is the relationship between a distance on a map and the same distance in real life. A map with a scale of 1:100 000 means that 1cm on the map equals 1km on the ground.

T - Title

The map title is the part of a map’s layout that describes the subject matter of the map. The title should instantly give the user a good idea of what the map is depicting. If the map is part of a series, then the title should clearly state which map it is and which series it is part of.

U - User requirements

An effectively designed map is one in which the intended message is clearly communicated to the map user. This is only possible by fully understanding what that message is and how the map is intended to be used.

V - Visualisation

Visualisation is at the core of what our GeoDataViz team do here at Ordnance Survey. They are responsible for making sense of complex data through compelling visuals in the most effective ways.

W - Web

Web maps are served and powered by the world wide web. They allow us to add interactivity and share our data or tell stories. Tiled web maps are displayed in a browser by seamlessly joining dozens of individually requested image files over the internet, and vector tiles are geographic data, packaged into small chunks which are then transferred over the web.

X & Y

X and Y refers to longitude (X) and latitude (Y) which are lines used on maps to easily locate places on earth. Longitude is the distance east or west of the prime meridian whilst latitude is the distance that is north or south of the equator.

Z - Zoom

Along with pan, tilt and rotate, zoom is one of the most common ways to navigate a web map. We have just launched our OS Open Zoomstack trial. Use the vector tiles to add slick, seamless zoom to your map application.