A method comprising: obtaining displacement sensor data about a measured distance of a non-contacting electromagnetic sensor array (100, 300, 500, 2120) relative to a surface of a Hot Mix Asphalt; comparing the displacement sensor data with reference displacement data to determine whether the sensor array (100, 300, 500, 2120) is at a reference distance relative to the surface of the HMA to secure an impedance measurement; in response to determining that the sensor array (100, 300, 500, 2120) is located at the reference distance, instructing the sensor array (100, 300, 500, 2120) to transmit a set of electromagnetic signals into the HMA; obtaining a return electromagnetic signal from the HMA; and calculating impedance characteristics of the HMA based upon the transmitted set of electromagnetic signals, the return electromagnetic signals, and the measured displacement data, correlating the calculated impedance characteristics with a density of the HMA, in response to determining that the sensor array (100, 300, 500, 2120) is located at a distinct distance from the surface of the HMA other than the reference distance, modifying the distance of the sensor array (100, 300, 500, 2120) such that the distance of the sensor array (100, 300, 500, 2120) will coincide with the reference distance, and after the modifying of the position of the sensor array (100, 300, 500, 2120), repeating the obtaining of the displacement sensor data about a measured distance of the sensor array (100, 300, 500, 2120) relative to the surface of the HMA and the comparing of the displacement sensor data with reference displacement sensor data to determine whether the sensor array (100, 300, 500, 2120) is at the reference distance relative to the surface of the HMA. obtaining displacement sensor data about a measured distance of a non-contacting electromagnetic sensor array (100, 300, 500, 2120) relative to a surface of a Hot Mix Asphalt; comparing the displacement sensor data with reference displacement data to determine whether the sensor array (100, 300, 500, 2120) is at a reference distance relative to the surface of the HMA to secure an impedance measurement; in response to determining that the sensor array (100, 300, 500, 2120) is located at the reference distance, instructing the sensor array (100, 300, 500, 2120) to transmit a set of electromagnetic signals into the HMA; obtaining a return electromagnetic signal from the HMA; and calculating impedance characteristics of the HMA based upon the transmitted set of electromagnetic signals, the return electromagnetic signals, and the measured displacement data, correlating the calculated impedance characteristics with a density of the HMA, in response to determining that the sensor array (100, 300, 500, 2120) is located at a distinct distance from the surface of the HMA other than the reference distance, modifying the distance of the sensor array (100, 300, 500, 2120) such that the distance of the sensor array (100, 300, 500, 2120) will coincide with the reference distance, and after the modifying of the position of the sensor array (100, 300, 500, 2120), repeating the obtaining of the displacement sensor data about a measured distance of the sensor array (100, 300, 500, 2120) relative to the surface of the HMA and the comparing of the displacement sensor data with reference displacement sensor data to determine whether the sensor array (100, 300, 500, 2120) is at the reference distance relative to the surface of the HMA.