In this erratum Fig. 3 of Opt. Lett.44, 1011 (2019)OPLEDP0146-959210.1364/OL.44.001011 has been updated. A diagnostic method for the electron plasma density and temperature based on the exploitation of wide-band THz pulses is presented. The model accompanying the diagnostic method is described and it is shown useful to characterize the plasma density and temperature profile along a symmetry axis. This diagnostic is particularly interesting for plasma-acceleration schemes or laser-produced plasma channels.