The ability to obtain reconstructed floor maps of acceptable quality with less samples speeds up the acquisition phase, which is of the highest relevance for most radio-frequency (RF)-based through-the-wall mapping (TWM) applications, particularly in the area of law enforcement and security. The key issue impacting the acquisition time is the quantity of necessary samples for acceptable floor reconstruction quality, which in turn depends on the intersample distance. We evaluate the impact of enlarging the intersample distance in the reconstruction quality of an algebraic method applied to RF-based TWM, under a parallel-beam acquisition geometry. Finite-element method (FEM) is used to define a physical model, allowing high accuracy in the simulation results. Two test floor maps are built in the FEM model, and the correspondent very-high frequency RF samples are generated in each case, composing the so-called sinograms. The sinograms are forwarded to the algebraic reconstruction method—simultaneous iterative reconstruction technique—to provide estimates of the original floor maps. In simulations, the use of sinogram upsampling to improve image resolution leads to floor maps of acceptable reconstruction quality in a parallel-beam RF-based TWM setup with intersample distances up to two wavelengths for an angular step of 4.5 deg.