Abstract: The precision measuring apparatus comprises a portal mounted to translate on a platform and comprising two uprights supporting a first cross-piece along which runs a carriage bearing a measuring head. The weight of the carriage is unloaded through resilient means on to a second cross-piece disposed parallel to and below the first cross-piece. The second cross-piece is a part of a second portal having two columns translating on the platform together with the first portal. The columns of the second portal are disposed inside the uprights of the first portal, which uprights are hollow, and are moved by the upwriters by means of opposed pairs of compression springs disposed between each column and the corresponding upright.