Context :

Aims : We provide new constraints on the chemo-dynamical models of the Milky Way by measuring the radial and vertical chemical gradients for the elements Mg , Al , Si , Ti , and Fe in the Galactic disc and the gradient variations as a function of the distance from the Galactic plane ( Z ) .

Methods : We selected a sample of giant stars from the RAVE database using the gravity criterium 1.7 < \log g < 2.8 .
We created a RAVE mock sample with the Galaxia code based on the Besançon model and selected a corresponding mock sample to compare the model with the observed data .
We measured the radial gradients and the vertical gradients as a function of the distance from the Galactic plane Z to study their variation across the Galactic disc .

Results : The RAVE sample exhibits a negative radial gradient of d [ Fe / H ] / dR = -0.054 dex kpc ^ { -1 } close to the Galactic plane ( |Z| < 0.4 kpc ) that becomes flatter for larger |Z| .
Other elements follow the same trend although with some variations from element to element .
The mock sample has radial gradients in fair agreement with the observed data .
The variation of the gradients with Z shows that the Fe radial gradient of the RAVE sample has little change in the range |Z| \lesssim 0.6 kpc and then flattens .
The iron vertical gradient of the RAVE sample is slightly negative close to the Galactic plane and steepens with |Z| .
The mock sample exhibits an iron vertical gradient that is always steeper than the RAVE sample .
The mock sample also shows an excess of metal-poor stars in the [ Fe/H ] distributions with respect to the observed data .
These discrepancies can be reduced by decreasing the number of thick disc stars and increasing their average metallicity in the Besançon model .

Conclusions :