Units for Unit Velocity

This article is about units of distance and time for in game units such as SCV’s and Marines. Unfortunately, that may be confusing because the word unit is being used for two different purposes in the same sentence. The different in game units in SC2 move at different speeds and that information can be looked up either in the map editor or online, for example at SC2Pod Wiki. Everywhere I looked, the movement speed of an SCV is stated as 2.8125, but the units of measurement are not reported. Without units, that number is meaningless except for comparison with other units. Even if some units such as “feet per second” were given, it still wouldn’t be useful, without some indicator of how far a foot in the game is, such as is provided by a legend in most maps. Another consideration is the fact that there are different game speeds and so we would need to know at which game speed the game seconds correspond to real life seconds.

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.

SCV Experiment Setup

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.

$\frac{16 \text{ grid lengths}}{5.79 \text{ seconds on normal speed}}= 2.76 \frac{\text{grid lengths}}{\text{seconds on normal speed}}\approx2.8125\frac{\text{?}}{\text{?}}$

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.

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