I find the easiest way to get a reasonably exact figure is to do multiple scans. What you're looking for is actually the most inaccurate scans.

Example:
Actual unit number: 50
4x scans say: 33, 68, 46, 71

You then work out the maximum/minimum it could be from the largest and smallest numbers.

Smallest number: 33
33 = 66 - 50% therefore you know that the 33 result means that the real number cannot be above 66.

Largest number: 71
71 = 47.3 + 50% therefore you know that the 71 result means that the real number cannot be below 47.3 (47)

Using this method you now know that your real number is between 47 and 66. Using advanced scans/more scans produces a more accurate outcome. Depends how much energy you can spare.

wow thats surprisingly helpful. Thanks!

may i point out that the ~ symbol actually means roughly equivalent too suggesting that normal military scans have an accuracy of roughly 50% meaning the scan can be anywhere up to 54.5% accurate. However if the use of the symbol ~ in game is not actually anything other than meaning =50% accuracy then i feel that it should be replaced as it contravenes mathematics. Thanks and hopefully that one can be cleared up.

Scans are given the ~ due to the fact that the can results vary by the figure given. Making a scan say =50% would be inaccurate as the scans are (almost never) exactly accurate. You appear to have misunderstood how scans in BD work, or I've misunderstood your post.

Everything here is great! This is pretty thorough. Another thing that you could use is to check their statistics if it is early in the era. That will give you the maximum amount they can have in their colony. It is 100% accurate.

I agree with everything except advanced scans are only 25% accurate the regular scans are 50% accurate. So it would make more sense just to run more regular scans then advanced ones especially since the advanced ones cost more energy. Tho the method you gave was a great one and I suggest everyone use it.

~50% means there is a potential variation of 50% (100 units could show between 50 and 150)

~25% means there's a potential variation of 25% (100 units could show between 75 and 125)

The ~25% result is more accurate, not less. Also both scans can produce either 50% or 25%.