A recent post by Aydin about trains from above piqued my interest. At first, I looked at his interpretation and, being something of a railfan, I felt that I could correct and supplement his interpretation.
At first, I discounted his interpretation of the two darker-roofed cars on the left side. But, trying to be objective, I had second-thoughts. I can't just discount his interpretation based on my assumptions. I have to be able to falsify interpretations. Really, a wonderful application of science. So lets look more closely at his photo and interpretation. This photo below is taken from his site and his arrow points to what he interprets as the two engines of the train. The primary question he asks was "how can you tell what direction the train was going based on a satellite photo?" I'll get to that question later, but first, lets address Aydin's interpretation of "engines" on the left side of the string of cars:
Here is his closeup:
Aydin's interpretation that these two cars on the far left were engines. I discounted this - why did I? Because in general, locomotive engines have distinct roof-top characteristcs that would stand out even in satellite view:
Here's a slightly more oblique view of an enigne pulling a train of boxcars. Note the distinct patches on the top of the engine.
Big thing is the three large circles on the long end. These radiator fans (some have two, some have three) are extremely common. However, not all locomotives have these fans (this is what I jumped on first, but if one must be objective, we have to determine if this assumption is valid). However, all diesel locomotives have some kind of dark grille on their tops. There are some darker spots on those two cars in the above satellite photos. But, they aren't in distinct circles or rectangles which nearly all locomotives have.
However, there are electrified locomotives which are relatively box-like and don't have obvious grilles on top. But the boxes on top of the locomotives to hold the pantograph (the thing that touches the overhead wires) stands out. The tops of the cars on the far left of the satellite photo are smooth (albeit a little darker than the others).
The only difinitive characteristic that I don't see is the windshield. All locomotives have at least a little break in their shape at the location of the windshiled. Given the lack of radiator grilles and windsheild break, I am interpreting those end cars as boxcars. The beauty of interpretation of observed data is that I might be wrong. I would imagine someone could put forth a set of characteristics that would contradict my interpretations (which is different from Aydins'). It's science with all the warts and wrinkles that personal interpretation brings with it.
So, to answer Aydin's question: what direction is a train going? That's an answer for the next post.