I opened the map editor to see if it could help me figure this problem out. It turns out that there is an option to display a grid that overlays the map and each of the grid squares has a width and height that corresponds to the unit of length referred to implicitly in the SCV velocity. I also ended up figuring out that the unit of time is one second when playing the game at “normal” speed. I initially guessed and hoped that those would be the units, but I verified it through an experiment.
The picture above shows the map I made to test my hypothesis. I had an SCV get a running head start so he would be at full speed by the time he reached the first vertical red line, at which point I started my stop watch. I then stopped my stop watch when he reached the final vertical red line. I added the roads along the vertical red lines, because the grid isn’t displayed outside of the map editor, and I loaded the map into the game by selecting “Test Document” in the drop down menu of the map editor. The amount of time it took the SCV to travel accross 16 grid lengths was 5.79 seconds.
Since 2.76 is very close to 2.8125 I assume that I’m correct about my interpretations of the units for distance and time, and that the error of 0.05 is due to the imprecision of my hand eye coordination using the stop watch.