Assuming a TOE of 100%.
The impact on CV is visible in the CV predictor Tooltip, so it's just to see the general impact.
(1) In dense terrain, the CV of infantry type ground elements is doubled and the CV of
AFV and combat vehicle type ground elements are halved (23.8.3).
(2) In double dense terrain the CV of infantry type ground elements is quadrupled (x4)
and the CV of AFV and combat vehicle type ground elements is quartered (x1/4).