Any of the links posted in this thread are dead 404 links. So I cannot verify the numbers you supposedly take from these "photo's". But yes, the basic equation is actual distance= actual height / observed height, times some correction factor. What that correction factor is, depends on the mod/ or particularly used scale. And technically the zoom factor too.
In the end it doesn't matter when you measure the vertical scale with angles in degrees or radians or whatever. They are slopes that mean a certain rise over a certain distance. For small angles like this, it doesn't matter if you convert a degree or a small fraction of a radian to a slope with the sin or tan scale. They are very much the same. The curves move apart when you get nearer to 45 degrees (or pi/4; halve of square root 2 versus 1) and ultimately towards 90 degrees (halve pi ;1 versus infinity). For small angles it makes no difference in the calculation.
If you want to know the conversion factor used at the end you just work that formula back with known value to find the unkown: the conversion factor:
You know range, you know actual height, you know observed or measured height.
correction factor = actual distance * observed height /actual height
The units for distance or observed height and actual height are not important either, as long as you use the same through out. You measure distance in meters, then keep doing that in meters. If observed height is in scale tickmarks then tickmarks is it. Actual height can be in meters, or the stack number of shoe-boxes. How they relate all end up hidden in the conversion factor. The correction factor is unit-less in essense. Meters divided by meters times some arbitrary sized tickmark interval on screen (pixels if you want). A different zoomlevel just gives you another correction factor to multipy into it.
There is not much to get deeper into the matter really.
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