See Cohen, 134 N.H. at 427, 593 A.2d at 1147 (standard for reviewing nonconforming uses). The landowner who claims a vested right bears the burden of proving all necessary elements establishing that right. New London v. Leskiewicz, 110 N.H. 462, 467, 272 A.2d 856, 860 (1970). We uphold the trial court's findings of fact unless (1) the trial court did not properly defer to the ZBA's fact finding, see RSA 677:6 (1986), or (2) its findings are unsupported by the evidence, see Cohen, 134 N.H. at 426, 593 A.2d at 1146.