[en] The yield ratios of neutron/proton (R(n/p)) and ${}^3\text{H}/{}^3\text{He}$ ($R(t/{}^3\mathrm{H}\mathrm{e})$) with reduced rapidity from 0 to 0.5 are investigated for 50 MeV/u ${}^{42,44,46,48,50,52,54,56}\text{Ca}+{}^{40}\text{Ca}$. This was conducted at whole reduced impact parameters using the isospin-dependent quantum-molecular-dynamics model in which the initial neutron and proton densities are sampled within the Skyrme–Hartree–Fock model, using which the neutron skin thickness ($\mathrm{\Delta <!--\; ??\; -->}{R}_{\mathrm{n}\mathrm{p}}$) is determined for different neutron-rich Ca isotopes. The results show that both R(n/p) and $R(t/{}^3\mathrm{H}\mathrm{e})$ have strong linear correlations with $\mathrm{\Delta <!--\; ??\; -->}{R}_{\mathrm{n}\mathrm{p}}$ of different Ca isotopic projectiles from five different centralities. It is suggested that R(n/p) and $R(t/{}^3\mathrm{H}\mathrm{e})$, from the same centrality, could be treated as possible experimental observables to extract the neutron skin or halo thickness for neutron-rich isotopic nuclei, including the nuclei near the neutron drip line.