▁two ▁main ▁categories : ▁( i ) ▁floor - based , ▁and ▁( ii ) ▁in - sh oe . ▁The ▁underlying ▁technology ▁is ▁diverse , ▁r anging ▁from ▁pie zo elect ric ▁sensor ▁arrays ▁to ▁light ▁ref raction , G ef en ▁A ▁ 2 0 0 7 . ▁Press ure - sens ing ▁devices ▁for ▁assess ment ▁of ▁soft ▁t issue ▁loading ▁under ▁b ony ▁prom in ences : ▁techn ological ▁concepts ▁and ▁clin ical ▁util ization . ▁W ounds ▁ 1 9 ▁ 3 5 0 - 6 2 . R osen baum ▁D , ▁Be cker ▁H P ▁ 1 9 9 7 . ▁Plant ar ▁pressure ▁distribution ▁measurements : ▁technical ▁background ▁and ▁clin ical ▁applications . ▁J ▁Foot ▁An k le ▁S urg ▁ 3 ▁ 1 - 1 4 . ▁but ▁the ▁ult imate ▁form ▁of ▁the ▁data ▁generated ▁by ▁all ▁modern ▁techn ologies ▁is ▁either ▁a ▁ 2 D ▁image ▁or ▁a ▁ 2 D ▁image ▁time ▁series ▁of ▁the ▁press ures ▁acting ▁under ▁the ▁plant ar ▁surface ▁of ▁the ▁foot . ▁From ▁these ▁data ▁other ▁variables ▁may ▁be ▁calculated ▁( see ▁data ▁analysis .) ▁ ▁The ▁spatial ▁and ▁temporal ▁resolution s ▁of ▁the ▁images ▁generated ▁by ▁commercial ▁ped obar ographic ▁systems ▁range ▁from ▁approximately ▁ 3 ▁to ▁ 1 0   mm ▁and ▁ 2 5 ▁to ▁ 5 0 0   Hz , ▁respectively . ▁S ensor ▁technology ▁limits ▁fin er ▁resolution . ▁Such ▁resolution s ▁yield ▁a ▁contact ▁area ▁of ▁approximately ▁ 5