Poison Ivy comes in several forms and there seems to be some debate over even the Latin name. Some authorities put it in the genus Rhus and some in the genus Toxicodendron. Some stop with the species name radicans while others split it into two varieties or subspecies, negundo or rydbergii. On the ground it may present itself as a creeping vine, a very small ankle high shrub, a taller, hip high shrub, or a vine that climbs high up in trees and sends out "branches" that may be up to a metre (3 feet) long.
Yesterday, on a Field Botanist of Ontario outing, we saw the largest shrub variety of poison ivy that I have ever seen. It was located by the shores of the Niagara River a few hundred metres downstream from the Whirlpool Rapids growing on a large rock. It was large enough that a footpath, used by fishermen I suppose, went under it. (I bet they are puzzled as to how they got poison ivy on their necks.)
Yes, all those wonderfully green leaves across the bottom of the photo and the shrub like branches below them are part of the poison ivy plant.