Archive Science

Asteroid 2011 MD passes through the Earth’s GPS satellite network Chris McDowall Jun 27


Tomorrow the ten metre wide Asteroid 2011 MD will pass within 12,000 km of Earth. How close is that? Well, it’s close enough that it will travel through the network of GPS satellites that circle the Earth. Pasquale Tricarico, a Research Scientist at the Planetary Science Institute in Tucson, Arizona, has created a series of animations describing the event’s geometry.

I have embedded my favourite visualisation from the series below. It depicts the encounter from the point of view of the asteroid. Amazing.

Thanks to Michele Bannister for sharing the link.

Ring of Fire – Animated Map of World Earthquakes (Jan 1 – Mar 12, 2011 GMT) Chris McDowall Mar 13


This video was made very quickly and could use some work. I post it here in case you find it interesting. I suggest you watch it full-screen, in high definition with scaling off.

The animation depicts two and half months of 2011 USGS earthquake data. Blue circles represent deep seismic activity recordings (>= 40km deep). Red circles represent shallow seismic events (<40km deep). Each event leaves behind a red dot to show the overall pattern. The animation ends the day after the 8.9 quake that hit Japan on March 11 and includes the shallow 6.3 Christchurch quake.

I am keen to spend some time improving this animation. Perhaps I will find some time in the coming weeks. I intend to release the programming code as an open source project – I would love to see the community build on this stuff.

Friday morning video – Powers of Ten Chris McDowall Oct 29

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This classic short documentary from 1977 helps viewers conceptualise the relative sizes of things in the Universe.

Powers of Ten begins with a one meter wide scene viewed from a distance of one meter. Every ten seconds the camera zooms in or out by a factor of ten. It seamlessly transitions from galactic vistas to scenes rendered at sub-atomic scales. It’s twenty years since I first saw this film and I still find it breathtaking.

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The film has been remade several times. Here’s an impressive recent version from the Imax film Cosmic Voyage. Morgan Freeman provides the voiceover.

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… and the obligatory Simpson introduction.

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Friday morning video – Asteroid Discovery From 1980 – 2010 Chris McDowall Sep 10

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An incredible video created by Scott Manley shows the locations of known asteroids starting in 1980. As asteroids are discovered they are added to the map and highlighted white so you can pick out the new ones.

Armagh Observatory host a current map of the solar system where you can see a two dimensional projection of known near-Earth objects.

Bump up the resolution, dim the lights and full-screen it. (via BoingBoing and @auchmill).

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Six months of seismic activity in under a minute Chris McDowall Sep 08


I created a video to animate six months of 2010 New Zealand seismic activity data picked up by the GeoNet sensors. The animation begins in April and ends a few days after the 7.1 quake that hit Christchurch on September 4. Keep in mind three things when you view the video.

  • Blue circles represent seismic activity recordings.
  • Each event leaves behind a small, pale red dot to show the overall pattern.
  • Most events are either small, deep or both.

Note how sparse the pattern of spots across Canterbury is until early September.

The data comes from the excellent folks at the New Zealand Geonet project. You can download the data as a spreadsheet from

I created the individual animation frames using Python and matplotlib. I stitched the images together with FFmpeg. I acknowledge the New Zealand GeoNet project and its sponsors EQC, GNS Science and LINZ for providing the data.

Two Christchurch quake animations Chris McDowall Sep 08


A quick post to note that Paul Nicholls has created a nice animation of the Christchurch Quake Map. He’s representing several variables at once. In addition to location and time, he depicts both magnitude (circle size) and depth (circle colour) while providing a running textual report of seismic events. It is well worth checking out.

Christchurch Quake Map

I started creating my own animated map on Tuesday morning. You can see my experiment here. I am happy with how the information is presented but unfortunately I do not have the time this week to take it any futher (e.g. adding time controls, refining layout, handle mobile devices). In the interests of pushing the Christchurch quake map site forward, I have shared my code with Paul.

A screenshot from the quick earthquake animation test I made. Click the image to see the animation.

A screenshot from my quick earthquake animation experiment. Click the image to see the animation.

Hand drawn chart of aftershock intensity Chris McDowall Sep 06


Mike Dickison, from the excellent Pictures of Numbers information design blog, has been working with GeoNet’s seismic data. This morning Mike asked the Internet “has anyone produced a graph of all the aftershocks and their intensity over the past two days?” It seemed that nobody had, so he created his own … by hand.

The figure below is a scanned copy of Mike’s bar graph of aftershocks following the large quake. Note the tall line at the far left of the chart. That is not the Y axis – that’s the big one.

A chart created with actual graph paper is a rare and wonderful thing. This made my day.

2010 Christchurch earthquakes aftershocks

Mapping quakes in Canterbury Chris McDowall Sep 05


I awoke yesterday morning to a stream of tweets and news articles reporting a massive earthquake near Christchurch. I followed the coverage throughout the day, reading the surreal accounts of everyday scenes turned upside down. Every so often an aftershock would ripple across Twitter and I would get a sense of the rhythm, if not the magnitude, of the event.

This morning I decided to try and map the data myself. I downloaded the seismic activity data from the GeoNet data portal. GeoNet is a joint geological hazard monitoring project between GNS and the Earthquake Commission. One of the great things about GeoNet is the fact that their data is freely available for researchers and members of the public to download and analyse.

Late this morning I wrote a short programme to parse the GeoNet data and generate a storyboard of maps to visualise the pattern of seismic activity for Canterbury on September 4. Each map represents one hour. The circles represent seismic events, centered on the quake’s epicenter. The larger the circle, the higher the quake’s magnitude. I have neglected to include a legend – it’s Sunday afternoon now and my dogs are begging to be walked – but the magnitudes can be inferred by examining and comparing the maps’ “largest magnitude” values.

If people are interested I can update the maps later this week to include the many aftershocks that occurred today.

UPDATE (Sunday) : John Fouhy has threaded the maps together into a cool animation. Nice!

UPDATE (Tuesday) : Paul Nicholls has created an animation of the last few days. It’s definitely worth checking out.

See the original set of quake maps below.

Seismic activity in Canterbury (Sunday, September 5)

Seismic activity in Canterbury (Saturday, September 4)

Why visualise data? Chris McDowall Sep 03


Why visualise data? In the introduction to his classic text, The Visual Display of Quantitative Information, Edward Tufte answers this question in three words. “Graphics reveal data”.

To illustrate his point Tufte asks the reader to examine four datasets of eleven (x, y) datapoints, collectively known as Anscombe’s quartet. I’ve reproduced them in the figure below.


The datasets that constitute Anscombe’s quartet share identical basic statistical properties and can be described by the same linear model. Take a look at them. What can you see? If you’re anything like me, the answer is probably “not very much”.

When the data is graphed their characteristics and differences become immediately apparent.


Visualisation renders complex data accessible. Graphics and interactive visualisations make visible things we never expected to see. They lend tangibility to abstract concepts, reveal patterns and highlight outliers. Good visualisation tells stories, surprises us and challenges our assumptions.

This blog will examine the state of data visualisation in New Zealand and abroad. I plan to draw attention to the interesting, the timely and the beautiful. I hope you will join me.

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