In this study we present one example of application of the databases collected in low ionospheric monitoring by VLF/LF radio waves relevant for the Earth's observations and positioning by SAR and GNSS signals. We analyze contribution of the perturbed ionospheric D-region in propagation delay of this signals and the results of this analysis indicate the need for inclusion of this atmospheric layer in modeling of SAR/GNSS signal propagation. Keeping in mind that its influence is usually ignored in modeling of the ionospheric influence on satellite signals, this conclusion can be of high priority in preciously positioning, Earth's observations, analyses and emergency responses to changes caused by natural disasters and in many other areas of human activities.