Abstract: A method and apparatus for detecting pipe entrenchment or upheaval of a flexible pipe and/or the presence of an external feature to the flexible pipe. The method includes helically winding a temperature sensing element around a layer of a flexible pipe, helically winding a heating element around a layer of a flexible pipe, heating the heating element to a pre-determined temperature, measuring the temperature at at least two locations along the flexible pipe, comparing the measured temperature response at the at least two locations, and making a determination, from the comparison of measured responses, regarding the exterior vicinity of the pipe at one of the at least two locations.