The composition of ultra-high energy cosmic rays is still poorly known and this is an very important topic in the field of high-energy astrophysics. We detect them through the extensive air showers they create after interacting with the atmosphere constituents.
The secondary electrons and positrons of the showers emit an electric field in the kHz-GHz range. It is possible to use this radio signal in 20-80 MHz for the estimation of the atmospheric depth of maximal development of the showers Xmax,
with a good accuracy and a duty cycle close to 100\%. This value of Xmax is strongly correlated to the nature of the primary cosmic ray that initiated the shower.
We present the importance of using a realistic atmospheric model in order to correct for systematic errors that can prevent a correct and unbiased estimation of Xmax.