Tuesday, November 18, 2008

Mapping Proportional Geographical Data

Reading a blog post by Jon Udell just now - Visual numeracy for collective survival - I came across this question:
What do you call th[e] kind of [map] projection, where country size is proportional to a variable?

What do you call something like this, for example?

example of a cartogram

Any ideas? How would you search for it?

I started off for a search on "proportional country map", and was lucky enough to soon hit upon an explanation by scanning through the search results: this type of map is called a cartogram, and it's one of several ways of using a map to depict the value of some particular measure or statistic.

Visit the Worldmapper website, which hosts a collection of several hundred different cartograms (some of which are reprinted in The Atlas of the Real World: Mapping the Way We Live) and see if you can find cartograms that estimate the distribution of telephone lines across the world towards the end of the 20th century and in the early years of the 21st century. What caveats are provided about the data used to draw the map? Do you find that you can make sense of the cartogram? How effectively does it communicate to you the relative distribution of telephone lines across the world? What data values are actually being visualised? What data values might have been visualised? How important is the selection of the data set for making a 'sensible' cartogram?

As well as cartograms, there are several other ways of visualising data overlays on a map. In Feel the Heat, I described how heat maps should be used to show the density of a particular measure over particular areas of a map by using a continuous, semi-transparent map overlay. (Geographical heat maps are often isopleth maps, where the different colours border on an "isobar" value or contour line: one one side of the line, the value is higher than the cotour line value, on the other side, it is lower.)

Two other popular techniques are widely used to associate more 'discrete' data values with either administrative areas (counties, states, and countries, and so on) or particular locations.

Choropleth maps

Choropleth maps use shading or different colours (often along a spectrum) to colour different well defined areas of a map. The Many Eyes World Map provides a quick and easy way of plotting choropleth maps.

Proportional Symbol Maps

Proportional Symbol Maps,or more often Proportional Circle Maps associate a particular symbol, typically a cricle, with a particular point on a map, such as the centre of a city, or the capital city of a country. The diameter of the circle is then some function of the quantity being visualised. The Many Eyes World Map can be used to create proportional circle maps, as can the map maker tool on Goecommons.com.

One of the useful features of the Worldmapper site is that it makes the data that was used to create the cartograms available, which means that you can download and visualise it for yourself using whatever mapping tools you have available. Download the small Excel spreadsheet containing the data for the most recent telephone lines distribution. Open the spreadsheet file, select an appropriate set of data, and upload it to Many Eyes. Once it is uploaded, create appropriate choropleth and proportional circle map visulisations of it. Which mapping technique do you find more powerful, and why? The choropleth map, the proportional circle map or the cartogram?

See also: Perceptual Scaling of Map Symbols (from the making Maps: Digital Cartography blog).

PS you can create you own choropleth and proportional symbol maps using a variety of UN data sets, in a browser, at StatPlanet.

Wednesday, July 16, 2008

Interactive Graphics: Phases of the Moon

Sometimes, and animation can be used to explain or illustrate a process, or demonstrate how something that changes over time actually 'works'.

Where the animation is made interactive, this allows the audience to engage with the explanations, 'ask questions of it' and test out their own hypotheses or questions about how things might change in a particular situation.

For example, the following screenshot is taken from an interactive application that demonstrates how the different phases of the moon appear to come about:

Phases of the moon interactive ( http://highered.mcgraw-hill.com/sites/007299181x/student_view0/chapter2/lunar_phases_interactive.html )

You can try out the interactive animation here: Astronomy: Journey to the Cosmic Frontier (Mcgraw-Hill) interactive: "Lunar Phases Interactive".

Even though no textual explanation is given about how the different phases of the moon appear to us on earth, do you think you could provide an explanation of the effect simply based on the above graphic? What explanation do you think the image provides, and how does the graphic manage to communicate it? Do the elements of animation and/or interactivity help to explain the effect 'in more detail', and if so, how?

Saturday, July 12, 2008

Social Visualisation of Baby Names

In A Round Chart in a Square Hole - Stacked Bar Charts, I showed how several data points could be plotted on top of each other in a variant of a bar chart known as a stacked bar chart.

Another bar chart variant - a grouped bar chart - can be used to compare data from different classes, and at different times, as this example shows:

Try to find a data set that can be sensibly visualised using a grouped bar chart, and create a chart with that data using the Google Chart Generator or within Google Spreadsheets or another online service.

If you found a data set that included several related classes of data collected over many dates, you might find that there are too many bars that can be grouped sensibly.

In this case, it might be useful to be visualise the data using a technique that allows for stacked data to be represented using a stacked line graph.

The Baby Name Voyager provides an interactive example of just this approach.


Visit the Baby Name Voyager website and have a play with it. As you do so, try to identify what the underlying data set might be, how it is visualised, and what sorts of interactivity are described. When this website was first released,. it was very popular and attracted a large number of visitors. What different reasons can you think of for why anyone would want to explore the name data using the name voyager?

Now read the following paper about the Baby Name Voyager by its creator, Martin Wattenburg, and see if you can answer the questions that follow below: Baby Names, Visualization, and Social Data Analysis.
  • What prompted Wattenburg to create the visualisation?
  • Where did the data come from?
  • How is the data visualised and what sort of interactivity is provided?
  • In your own words, how does Wattenberg describe the notion of "social data analysis"?
  • What sorts of "role" does Wattenberg suggest people fall into when socially analysing the data?

Wednesday, July 9, 2008

Satellite Coverage Maps

Just after I put together the post on Visual Teaching - GPS Satellite Constellations I came across a site that displays live satellite tracking on a map:

Live satellite tracking http://www.n2yo.com

The site allows you to track particular satellites, or view satellites that are in your particular bit of sky...

Even if a satellite is in line of sight with your location, however, it doesn't necessarily mean that you can get a signal from it. Many of the antennae on a satellite are directional. The rather wonderful SatBeams website shows actual satellite coverage maps for a selected satellite:

Satellite coverage maps - http://satbeams.com

Where does SatBeams claim to get its data from? Is this a trusted source? Does the satellite tracking data site offer any explanation of where it gets its data from, and if so, how does this compare with the SatBeams site?

How can visitors to the Satbeams site particpate by contributing data back to it? In what ways might this user contributed data add value to the site or detract from it?

As well as satellite locations, it's also possible to find locations for other transmitters. For example, here's a geo-referenced list of UK television and radio transmitters.

(If you come across any related lists, such as a list of UK mobile phone cell masts, please post a link in a comment to this post:-)

Friday, July 4, 2008

Creative Mapping

Most people are familiar with the idea of maps as representations of geographical information, and making judgements about distances between places, climate, and maybe even cultures as a result of where they are on a map.

By reading particular map features - such as mountain ranges, uncrossable rivers, jungles and oceans - we also get an idea of how much effort might be involved in crossing a particular sort of terrain.

So how about using maps to tell a different sort of story, such as how close different businesses are in cultural terms?

Here's a 'regional' map...

Or how about this map of a city?

How effective are these maps at implicitly communicating some sort of story about what they depict? For example, how is DRM (Digital Rights Management) or Microsoft depicted in "The Web is Agreement"?

Each of these maps can be used to tell a story. For example, here's a walkthrough of a social entrepreneurship landscape:

The social entrepreneur landscape from David Wilcox on Vimeo.

How are geographical features used in the social entrepreneurship landscape to bring alive the relationship between, or roles played by, different social entrepreneurs and socially minded organisations?

Saturday, June 28, 2008

Visualising Floor Plans - From 2D to 3D

If you are ever in the market for buying a house, it's likely that whenever you get the details for a property it will include at least a 2D hand-drawn sketch of the floor plan of the house.

However, it's increasingly likely that a more professional looking floor plan will have been created using a CAD (computer aided design) floor plan editor, such as the Autodesk labs online drawing tool. (It's possible to share such drawing over the web , so if you have a go at using the Autodesk Labs Draw package to draw a floor plan, please post a link back to it in the comments to this post :-)

2D floor plans are all very well, but there is also an increasing number of tools that make 3D modeling, a technology once only available to professional architects, now available to all-comers.

For example,, SketchUp is a 3D design tool that can be used to create 3D models of buildings (as well as other objects). SketchUp models can be displayed in Google Earth and used in other 3D web applications and virtual worlds.

SketchUp works on Mac and Windows computers and can be downloaded from http://sketchup.google.com/.

It is also possible to model - and view - objects inside building that you have created, as well as creating the buildings themselves.

In true collaborative style, you can share and edit the designs that other people have created by checking them out of the 3D Warehouse.

One very powerful feature of SketchUp is the ability to use a photograph as the basis for a model, as the following movie illustrates:

Download Google SketchUp and have a go at creating your own 3D model. There are lots of video tutorials to help get you started on both the Google SketchUp website and on YouTube. When you have completed your model, why not upload it to the 3D Warehouse, or post a movie of a walkthrough of your model to a video sharing site, with a link back here? :-)

Once you have created a 3D SketchUp model, it can be submitted to the Google Sketchup 3D model warehouse, and then viewed in 3D worlds such as Google Earth. Online applications such as Scenecaster also allow you to reuse models from the SketchUp warehouse as part of an animated 3D walkthrough, as this movie shows.

If you are interested in using SketchUp to create 3D models from 2D floor plans, this set of tutorial videos will show you how:

(Note that if you use the Autocad Labs Draw application cannot directly export drawings in a CAD format that SketchUp can import. However, you can export the plan as an image and load that into SketchUp, where you can trace round it.)

If you do manage to create a 3D model from a floor plan, why not post a link back to the original 2D CAD drawing, and the 3D model you generated from it, as a comment to this post?

Monday, June 23, 2008

Visual Teaching - GPS Satellite Constellations

When I set up the visual gadgets blog, the intention was to use it to draft out a set of materials about data visualisation. So how about this: visualising data about GPS satellite locations...

Google GPS satellites

The above image is taken from a visualisation using Google Earth, as described here: Interactive Spiders and Charts. The visualisation also supports an animated view, showing the motion of satellites over a 24 hour period. It's particularly interesting to watch how different satellites come in and out of view of a particular location.

To view the visualisation in Google Earth, Add the following Network Link in Google Earth: GPS Satellite constellation. (If I get a chance, I'll try to put together a page that works in the Google Earth browser extension, and maybe uses Milton Keynes as the focus? An interesting exercise would be to let the user create the KML file that visualises satellites in view for their own location...)

The following movie describes how the GPS system works:

To learn more about GPS, HowStuffWorks has a good intro to How GPS Receivers Work, but for a more detailed view, check out the MIT opencourseware courses GPS: Civilian Tool or Military Weapon? and Modern Navigation.