Recently the Holistic Engine Rotor Measurement System (HERMES) has been installed in the Dynamics Lab at Imperial College London. It allows us to study the complex vibration behaviour of a spinning gas turbine in a well-controlled laboratory environment. As part of the test facility, a 3D-SLDV system has been purchased to provide highly dense vibration information of the engine casing. A detailed study of the modal response of the casing has recently been conducted, highlighting some very interesting modal behaviour, especially across the many flange joints of the engine. This paper will discuss some of the challenges in setting up and aligning the 3D-SLDV system on a relatively small but highly curved surface, introduce some of the obtained response data and discuss the implications of using full field 3D measurements to monitor engine casings.