Add extra information to a map created by Gmapping

Dear all, I would like to add an extra information to a map created by gmapping. In fact, in addition to 2d coordinates and the Occoupancy Grid (-1: Unknow 0: Free 100: Occupied) of each cell, I wish to add the height of this cell from the ground. for example: the height of a table from the ground is 0.75 meters, for a ball; 0.30 meters ... Is there someone who did this before ? Best Regards.