Saturday, February 2, 2013

A little about the "Race Flow Chart"

The Yukon Quest started about six hours ago, and in a 1000-mile race that means that it's too early to know much about much.  But, I'm seeing some discussion on Facebook that makes me think that it might be helpful to explain a little about Trackleaders' "Race Flow" plot.

One of the things I really like a lot about Trackleaders is that they want to do more than just show you static positions on a map.  Those are definitely useful but they don't capture the general sense of what's going on.  I love using numbers to explain things but I am not a mathematician.  Numbers need to describe something going on in the world - they need to have descriptive power.  And I really think that the race flow plot does.  It's a really, really simple idea but it is incredibly elegant.  It shows the dynamics of the race

Here's the basic idea:  They have a two-dimensional graph.  The x-axis (the horizontal one) shows the race time (the number of hours since the race started.  The y-axis (the vertical one) shows the number of miles along the trail someone has traveled.  So, when they get a new tracker update for a given musher, they put a dot on the plot showing how many miles the team was along the trail at that point in time.  When you connect the dogs with a line, that line has slope - the steeper the slope, the faster the team was traveling, and the more level the slope, the slower the team was traveling.  If it's completely level, the team has stopped.

Here's a screen capture about 6.5 hours into the race:

You'll see that the lines are basically parallel, which shouldn't be surprising, especially not this early in the race.  You can take a look at the plot and by looking where the lines are, you can see things like that at about hour 5.5, Hugh was around mile 52 and Lance was around mile 49.  Similarly, you can see that Hugh passed mile 40 around 4 hours and 10 minutes into the race and Lance passed it around 4 hours and 35 minutes into the race.  You can get a sense of how far apart they are by measuring the distance between them on the y-axis (miles) at a given time.

So that's all great, but what really interests me are the stories being told here.  You can see that someone is catching up with someone else when their lines are converging (for example, Normand and Allen at about hour 6.5).  You can see when they're falling behind as their lines get further apart (for example, Randy Mackenzie falling behind Markus Ingebritsen at about 6 hours and 15 minutes).  You can see passes when their lines cross (Kelley Griffin passing Randy at about 4:15 into the race).  You can see who's traveling together (their lines are basically on top of each other, like Susie Rogan and Allen from about 5:45 into the race), and so on.  A very nice thing is that you can make some projections.  In this screen grab you can see that Hugh's tracker has been updating but Lance's hasn't (the most recent "breadcrumb" was received shortly before 6 hours into the race, while Hugh's updated about 6 hours and 40 minutes into the race.  But this plot allows us to get a handle on where they're likely to be in relation to each other, by extending the lines for each musher on the same slope the line's currently on.  From here, it looks like Lance is gaining on Hugh, but very, very slowly.  So, even without recent tracker updates you can get a rough handle on where they might be in relation to each other.

It would be fantastic if Trackleaders would extend the plot to allow us to choose which mushers to show, but as it stands it's still my favorite tool for getting a quick handle on how the race is going.


  1. Interesting. Would you make a flowchart about how to understand this whole race? Here's the perfect flow chart tool to do it with; it's fast and easy and you don't need to download anything. Thanks for your time