android - Different values of screen density -

i've defined item in values/dimen.xml value 48dp. when set height of view, in view hierarchy dump tool in eclipse, real height of view 72, 48*1.5, , seem legit in hdpi device (nexus 7). but, when load value piece of code:

float d = getresources().getdimension(r.dimen.dimension_name) 

,d 63, 48*1.3. running app on nexus 7 real pixel density 1.3, according this. doing wrong? there other way load dimension , real value (72)? or bug or something?

thanks in advance