Better Mapping Seminar

In October and November 2006, the British Cartographic Society ran a series of 1 day seminars on Better Mapping. This page is the notes and conclusions from attending the London seminar.

Contents 1 Summary 2 Talks 3 There are Good Maps and Bad Maps 4 Basic Principles of a Map 4.1 Projections 4.2 Spheroids 4.3 Datums 4.4 Reference Systems 4.5 Scale 4.6 Generalisation 4.7 Accuracy and Precision 4.8 Marginalia 5 Creating and Maintaining the National Mapping Archive 6 Copyright, IP and Legal Deposit 7 Advanced Cartography with GIS 8 How to Create A Better Map 8.1 Right Info 8.2 Title and Facts 8.3 Symbology 8.4 Colour In Maps 8.5 Labels and Text

Summary

• Use colour sensibly. Don't make everything the same colour, and don't re-use colours for different things (eg motorways and rivers)
• When reducing, remove features. Otherwise you end up with a very accurate, but totally unreadable map
• When enlarging, errors and changes that were hidden will probably show up, so where possible find a more accurate data source
• can't just haul everything out of a GIS and display it. Need to figure out what's important, then colour and highlight that so it stands out
• what is right for one situation is probably wrong for another. Will need to customise the map for the intended audience
• your GIS should hold everything, but your map should be filtered to only have the things it needs
• decide on the primary message of your map, and any secondary messages. Then make sure that your map shows those clearly

Talks

Many of the talks had lots of maps in them, which provided great examples of the points they were making. As yet though, none of the example maps are available online.

There are Good Maps and Bad Maps

• Many different kinds of maps, from atlases to street plans
• They come from different datasets, at different scales, for different places
• At Harper Collins, maps come out of the GIS, and are further edited in Illustrator and Quark Express
• Use your GIS to get out something close to a map
• Then use your cartographic skills to finish it off
• Key point of cartography is not what you put on a map, but what you leave off it. GIS normally has too much data, so you need to be selective
• Same principles apply no matter the medium (paper, book, web etc)

Basic Principles of a Map

• Elements
  • Projection, Spheroids, Datums
  • Grids and Reference Systems
  • Scale
  • Generalisation
  • Accuracy and Precision
  • Marginalia and Metadata

Projections

• Equal Shape - same shape as from space
• Equal Area - size is right, shape is wrong

Spheroids

• Mathematical expression of the shape of the earth
• Earth isn't a perfect sphere
• Optimise the mathematical shape to match the real shape for the region of interest

Datums

• Where sea level is defined at

Reference Systems

• lat+long normally not wanted, as the grid isn't square
• instead, project onto an easting+northing system

Scale

• Large scale map - big in detail, small in area
• Small scale map - small in detail, big in area
• Data will have been collected for display at a certain scale
• If you try to match datasets from different scales, will mis-match between features shown, how well they overlap etc

Generalisation

• If the capture resolution is greater than the output map will be, you'll need to generalise your data
• Generalisation involves removing points and simplifying shapes
• Where you can, use a symbol for something, rather than writing it out

Accuracy and Precision

• Precision is the level to which it is recorded, eg 1.0 vs 1.0021112
• Accuracy is the degrees of errors on it, eg +- 1.0 vs +- 0.005
• Data may be precise to 3dp, but source may only be accurate to 1dp, so despite how it looks (3dp), is only 1dp
• Classification accuracy - is that a haystack, or a thatched cottage?

Marginalia

• Title, legend, scale, when made, who made for, who made by, GIS source metadata etc

Creating and Maintaining the National Mapping Archive

Listen to an Ed Parsons interview. You'll learn more from it.

Copyright, IP and Legal Deposit

The speaker really needs some training, and to read anything by Laurence Lessig. The bits on Legal Deposits of maps was a little interesting though. Agency for the Legal Deposit Libraries

Advanced Cartography with GIS

• The ESRI tools let you do lots of really cool things
• You can make really really pretty maps with them
• They support really fancy techniques for shading, shadows, hills and lakes etc
• It's a shame that they cost quite so much
• They don't support importing of .osm files, but it shouldn't be too difficult to add it in

• gvSIG can make fancy maps.
• This tool has a little less options but they are coming fast.

How to Create A Better Map

• Selecting the right information
• Picking the right line widths, shading and symbols
• Importance of colour
• Text placement, and the importance of labeling

Right Info

• What is the map's function?
• What's the primary message? Are there any secondary messages?
• What's the map size? (A1? A4? 300px?). What's the scale?
• How accurate are your sources? What scales and audiences were they compiled for?
• Who's the intended audience? What do you want them to get from your map?

Title and Facts

• Get your title right
• Get your facts right
• If you have some empty space, can you put anything useful there?

Symbology

• Made up of lines, nodes and areas
• Decide what's important, less important
  • eg make motorways wider and darker
  • make B roads narrower, but change the colour so it doesn't blend into the colour picked for mountains
  • make A roads smaller and less bright than trunk roads
• Do the lines, symbols and shadings make the map functional?
• Is there a hierachy of line weights, shadings and symbols?
  • eg more important symbols are larger, bolder and darker

• common GIS problem - pavement is same line weight and colour as motorways and tower blocks!
• need to decide on a hierachy, then set weights and boldness as required
• black lines (eg on edges) make it dark, and normally harder to read
• if an area's colour is dark enough, you probably don't need black edges

Colour In Maps

• Do the colours and patterns support the hierachy? Do the most important things stand out?
• Are associated things represented in associated colours?
• Is there a subliminal harmony in the colours used?
  • eg most have 30% yellow, in addition to their other colours
  • eg most have 30% in at least one colour
  • studies show that if colours are in harmony, people tend to look at maps for longer
• on a map where reliefs are important, make sure colours make it easy to spot peaks, valleys and ridges
• death by colour - if too many, then the colours no longer enhance the readability of the map. instead, they distract from it
• when colour is just being used to identify areas that are the same (eg countries), ensure that the colours are evenly distributed

Labels and Text

• Get letter spacing right. Visual spacing is best (equal visual space between the letters)
• Spacing between words needs to be bigger than spacing between letters
• Spacing between lines needs to be bigger than the spacing between words
• Blocks of text need to be clearly separate, give them a bigger vertical spacing
• Words, when on a map, shouldn't overlap with other words

• Text placement, three things to consider
  • The actual text
  • The appearance of the text
  • The position the text occupies
• Try to place names away from busy areas and clutter
• If the names clash too much, make all of them a bit smaller
• If you have to run a name onto two lines, keep the spacing small so it looks like one unit
• If you have a small feature, then consider makings the labels on it smaller
• Make names as central as you can