A detector, comprising: one or more Light Detection and Ranging, LIDAR, devices on an aircraft (104, 500, 1004), each of the one or more LIDAR devices including a transmitter and a receiver, wherein: the transmitter is configured to repetitively scan an aerodynamic surface on the aircraft (104, 500, 1004) using laser pulses, forming scattered laser pulses (210, 220) scattered from the aerodynamic surface, the receiver is configured to receive the scattered laser pulses (210, 220) and output data comprising timing of the scattered laser pulses (210, 220) received in the receiver, the LIDAR devices are coupled to a computer (222, 1302) configured to calculate, from the data, temporal changes in coordinates of the aerodynamic surface that indicate a presence or absence of ice on the aerodynamic surface, characterized in that the data comprises a data set outputted for each of the plurality of scans representing the coordinates at different times, and for each of the data sets, the computer (222, 1302) is further configured to: extract a shape of the aerodynamic surface from the data set using a shape model; determine one or more deformations in the shape due to flexing of the aerodynamic surface due to weight of the wing (102, 508) and/or pressure of airflow over the wing (102, 508); transform the data set into common coordinates in a common reference frame using a transformation function, wherein: the common reference frame comprises the aerodynamic surface without the deformations, and the transformation function transforms the aerodynamic surface having the deformations into the aerodynamic surface without the deformations; temporal changes in the common coordinates in the common reference frame are used to detect the presence of the absence or the ice. the transmitter is configured to repetitively scan an aerodynamic surface on the aircraft (104, 500, 1004) using laser pulses, forming scattered laser pulses (210, 220) scattered from the aerodynamic surface, the receiver is configured to receive the scattered laser pulses (210, 220) and output data comprising timing of the scattered laser pulses (210, 220) received in the receiver, the LIDAR devices are coupled to a computer (222, 1302) configured to calculate, from the data, temporal changes in coordinates of the aerodynamic surface that indicate a presence or absence of ice on the aerodynamic surface, characterized in that the data comprises a data set outputted for each of the plurality of scans representing the coordinates at different times, and for each of the data sets, the computer (222, 1302) is further configured to: extract a shape of the aerodynamic surface from the data set using a shape model; determine one or more deformations in the shape due to flexing of the aerodynamic surface due to weight of the wing (102, 508) and/or pressure of airflow over the wing (102, 508); transform the data set into common coordinates in a common reference frame using a transformation function, wherein: the common reference frame comprises the aerodynamic surface without the deformations, and the transformation function transforms the aerodynamic surface having the deformations into the aerodynamic surface without the deformations; temporal changes in the common coordinates in the common reference frame are used to detect the presence of the absence or the ice. extract a shape of the aerodynamic surface from the data set using a shape model; determine one or more deformations in the shape due to flexing of the aerodynamic surface due to weight of the wing (102, 508) and/or pressure of airflow over the wing (102, 508); transform the data set into common coordinates in a common reference frame using a transformation function, wherein: the common reference frame comprises the aerodynamic surface without the deformations, and the transformation function transforms the aerodynamic surface having the deformations into the aerodynamic surface without the deformations; temporal changes in the common coordinates in the common reference frame are used to detect the presence of the absence or the ice. the common reference frame comprises the aerodynamic surface without the deformations, and the transformation function transforms the aerodynamic surface having the deformations into the aerodynamic surface without the deformations; temporal changes in the common coordinates in the common reference frame are used to detect the presence of the absence or the ice.