Buildings on lots which are crossed by the oceanfront building line shall not exceed 34 feet in height from an elevation determined by striking a line, perpendicular to the building line, at the elevation thereof and running to the lot elevation at the setback line at the opposite side of the lot from the building line. The thirty-four-foot height limitation is to be measured from the elevation established at the midpoint in the line so struck between the building line and the opposite side setback line.