Abstract: A pipeline survey pig includes an elongated hollow pig body having an enclosure for supporting a generally cylindrical tubular instrument chassis which, in turn, supports an inertial reference unit and associated signal processing and recording devices. A plurality of resilient cup members support the pig body for traversal through a pipeline section under the urging of pressure fluid. The cup members are spaced apart and secured to the pig body by spacer members which may be selectively provided to predetermine the axial spacing of the cup members so that the center of stiffness of the pig is in a predetermined position. The instrument chassis is secured in the pig body by a cam mechanism which is actuatable from one end of the chassis after insertion into the pig body to wedge opposed chassis door members into engagement with the pig body to enhance heat transfer between the chassis and the pig body.