# RTK F9P Drotek Modules

Unlike previous U-blox GNSS module generation, new **ZED-F9P high precision GNSS** module now handles **multi-band GNSS L1/L2** which implies better estimation and correction of ionospheric interferences.

![](https://3825805345-files.gitbook.io/~/files/v0/b/gitbook-legacy-files/o/assets%2F-LYSZeu4HjB-NrVI4riL%2F-LZ_8HkizV6u2BGOvi4D%2F-LZ_8MmFXWv40AA10eSb%2FF9P%20%3A%20M8P.png?alt=media\&token=d487ca96-868a-4f09-99cb-89f07ba4eabd)

Indeed, ionosphere is the layer of the atmosphere where gas molecules are ionized by UV rays coming from the sun. Therefore, free electrons may interact with the GNSS signal broadcasted by satellites causing severe delay effects. Knowing L1 & L2 frequencies do not react the same way when facing this atmospheric disturbance, delays may be **virtually eliminated** by double differencing on the GNSS receiver side, consequently i**ncreasing GNSS RTK position accuracy.**