Seismic noise of several sensors. The relative location of the recording points is needed more or less precisely for the different techniques, requiring either manual distance measurements or differential GPS location. The advantages of ambient vibration techniques compared to active techniques commonly used in exploration geophysics or earthquake recordings used in Seismic tomography. Limitations of these methods are linked to the noise wavefield but especially to common assumptions made in seismic: Seismic noise In geology and other related disciplines, seismic noise is a generic name for a relatively persistent vibration of the ground, due to a multitude of causes, that is a
Venus effect viewers see is different from what the actor sees, because the camera is not right behind the actor, but the position of the actor is often chosen so that his or her image is nicely framed in the mirror for the camera. Although the name of the effect refers to a woman, Venus, the effect is more general. The effect is seen with an animal apparently looking at itself in a mirror in "The Lady and the Unicorn" (French: "La Dame à la licorne") tapestries, where the unicorn appears to be gazing at its own reflection as it kneels on