Hello, my name is Rob Fatland and this is the first in an occasional blog primarily about earth system science. That is: The task of understanding our habitat using interwoven system models. 'Our habitat' now extends from -35,576 feet (10843 meters) thanks to James Cameron to +29,029 feet (8,848 meters) thanks to Tenzing Norgay and Edmund Hillary. And that's the last time I'll use English units, by the way; if Americans can follow the British into the intricacies of this bizarre language we can certainly follow them in the adoption of the metric system. Which brings me to today's topic, the interpolation of trajectories.
Do you write code? By which I mean, do you crawl under the hood of a computer, go behind the curtain, and direct its activity in some Great and Powerful Oz sort of way? I would consider "YES" accurate if you work with formulas in Excel, or if you use hypertext markup, or if you use JavaScript or Python or C or C# or MATLAB... the list goes on. There are lots of venues for making computers do what we want; and I have a very interesting such Want I chase after: A scientific objective that I work on in spare moments. I would like to predict the future of the northeast Pacific Ocean... and this pursuit led to an amusing bug the other day. So my story so far: Hello World to earth systems to metric units to computer programming to a Bug on the road to thinking about the future... here we go.
I use a virtual globe application called Worldwide Telescope (WWT) to draw and explore earth science data in geospatial context. This has advantages and disadvantages. The main disadvantage is that the necessary skills took a bit of work to develop. The advantage is that I can draw a million or more data points; and recently this has been about visualizing water flow in the coastal oceans. But the scientist I work with creates trajecotories as discrete locations sequential in time separated by a kilometer or more... and sometimes the water goes up and sometimes it goes down in depth. So I built -- with Nels Oscar, a grad student at OSU -- some code for interpolating these trajectories so that they render more smoothly. It is like filling in the gaps in a jumpy animation: If you provide some intermediate frames all the motion smooths out.
To see what I'm talking about, go to this link and click the Play button by the video: http://www.layerscape.org/Content/Index/1222
Well the bug was kind of goofy as all bugs are: I was choosing how many intermediate points to interpolate based on the distance between consecutive points... in depth, in longitude and in latitude. Of course 50 is much bigger than 0.01... so a 50 meter depth change overshadowed one hundredth of a degree of latitude change... I was treating apples of distance as oranges of distance; the results were not pretty at all. But easily remedied: Make everything apples and there we have it, smooth interpolated trajectories and we can return to exploring what those trajectories mean, the whole purpose of the visualization exercise. Two-dimensional charts serve just fine in many instances; but we need tools like WWT to see and think in four dimensions. (More on this at http://layerscape.org.)
So hello world, welcome to the earthscience blog, I must add 'made possible by Microsoft Research'. My game plan: Let's use technology to explore and better understand the earth; let's see where we're all headed, and if there is trouble ahead as we now suspect then let's see if we can't figure out how to change course for the better.