This paper is an analysis of how to improve and find a more stable method of measuring the position of a piston in a hydraulic cylinder/accumulator in heave compensated systems. It provides an investigation of whether a radar system can be placed within the cylinder to get close range distance readouts. Technologies for piston positioning already exist on the commercial market, but they all share one common flaw: they are mounted on the outside of the cylinder. Due to the harsh conditions at the installation site, these sensors are vulnerable to corrosion, mechanical wear, and damage. An intrusive system could overcome these problems and prove a more stable system installation. This paper links a specified radar system to the application of piston position measurement in heave compensation systems. In doing so the most common properties of a close range radar system are analyzed and mapped out. It also investigates which properties make a radar system suited for close range distance measurements, and identifies the associated problems. This paper provides both a mathematical analysis of the problem as well as a test implementation. An intrusive measurement system could provide a longer lasting sensor with less (or no) need forservice and thereby reduce both downtime and installation costs.