There are couple of entries in cfgVehicles that affect detection:
camouflage = 2; //how difficult to spot. The bigger value, the better is vehicle spot-able over distance. Tanks use 8, men 1, aircraft up to 100.
audible = 6; // similar camouflage but for sound. The bigger value, the better the unit is heard.
accuracy = 0,25; // accuracy needed to recognize type of this target. Usually varies from 0 to 2. The bigger value, the more time you need to recognize specific type. Value 1000 is used for object that should be never recognized, for example medic should be known as regular soldier.
spotableNightLightsOff = 0,05; spotableNightLightsOn = 4; // night spot-ability coefficients, defined only in core
sensitivity = 1; sensitivityEar = 0,0075; // sensor sensitivity, most vehicles see and hear less than man
vehicles also use some defines about laser/IR targeting...
irTarget = true; irScanRangeMin=0; irScanRangeMax=0; irScanToEyeFactor=1; irScanGround=true; laserTarget = false; laserScanner = false;
in cfgMoves there is also one parameter:
visibleSize = 1; //defined the same for all except prone and prone reload animations