A compact triple band antenna array for GNSS application, covers GPS L1, L2 and L5 frequency bands, is proposed in this paper. The array is comprised of 4 radiating elements spaced 0.47 wavelength apart (center to center) at the GPS L1 band and filled with dielectric material and three stacked patches. It is observed that due to the compactness of the antenna array the mutual coupling degrades the radiation properties. We present a modification in the ground-plane to mitigate the inter-element coupling and improve the axial ratio property. It reduces the axial ratio below 3dB in the main-lobe directions, which is required for the navigation systems.