question: Why do waves seem stationary when viewed from the airplane window?
comment: One major part it that a car move relative to stationary ground so it is quite easy to see that is move but out as sea all waves moves at relative same speed so to have a fixed point of reference you have to compare it to land. The next part is that waves are relative slow. Look at the [Beaufort\_scale]( URL_0 ) for the wind speed and the resulting waves. Look at Strong breeze where there start to be white crest on the waves the wind speed is 39–49 km/h and [the wave speed]( URL_1 ) then is in the 20-30km/h range compare to a car on a highway that travel at 4x - 6x time faster So next time compare a car in a at slow speed to a wave that hit the shore or move close to something stationary.
passages: Section::::Radar.
   However, the above equations represent a simplified model, as they assume that the reflecting waves are not moving. This is of course untrue and, because of the motion, the frequency of the scattered signal (and therefore its wavelength) is not the same as the one of the transmitted signal. In fact, “waves moving toward the receiver increase the return frequency, while waves moving away decrease the return frequency”.
   Even though the input transparency only occupies a finite portion of the "x"-"y" plane (Plane 1), the uniform plane waves comprising the plane wave spectrum occupy the entire "x"-"y" plane, which is why (for this purpose) only the longitudinal plane wave phase (in the "z"-direction, from Plane 1 to Plane 2) must be considered, and not the phase transverse to the "z"-direction. It is of course, very tempting to think that if a plane wave emanating from the finite aperture of the transparency is tilted too far from horizontal, it will somehow "miss" the lens altogether but again, since the uniform plane wave extends infinitely far in all directions in the transverse ("x"-"y") plane, the planar wave components cannot miss the lens.
   and
  
  and
  
  In the figure, the "plane wave" phase, moving horizontally from the front focal plane to the lens plane, is
  
  and the "spherical wave" phase from the lens to the spot in the back focal plane is:
   Section::::Types of devices.:Range gated imagers.
  
  These devices have a built-in shutter in the image sensor that opens and closes at the same rate as the light pulses are sent out. Because part of every returning pulse is blocked by the shutter according to its time of arrival, the amount of light received relates to the distance the pulse has traveled.
   where k is the spatial frequency and formula_2 is the amplitude of the jitter. Note that this frequency is in radians of phase per cycle. The equivalent expression in Hz is
  
  where u is the spatial frequency and formula_2 is again the amplitude of the jitter.
  
  For spacecraft, operation in a vacuum often means low mechanical damping. Meanwhile, spacecraft are compact and rigid, to withstand high launch loads. Jitter, then, is transmitted easily and often a limiting factor for high-resolution optics. 
   Section::::Modes.:Tropospheric modes.:Airplane scattering.
  
  Airplane scattering (or most often reflection) is observed on VHF through microwaves and, besides back-scattering, yields momentary propagation up to 500 km even in mountainous terrain. The most common back-scatter applications are air-traffic radar, bistatic forward-scatter guided-missile and airplane-detecting trip-wire radar, and the US space radar.
  
  Section::::Modes.:Tropospheric modes.:Lightning scattering.
   Nicholas Monsarrat, the novelist who wrote "The Cruel Sea", described the phenomenon in the Pacific Ocean in his unfinished final book "Master Mariner", which was partly inspired by this tale (he lived and worked in South Africa after the war) and the story of the Wandering Jew.
  
  Section::::Explanations as an optical illusion.
  
  Probably the most credible explanation is a superior mirage or Fata Morgana seen at sea.
   BULLET::::- Different modulation frequencies: If the cameras modulate their light with different modulation frequencies, their light is collected in the other systems only as background illumination but does not disturb the distance measurement.
   Section::::Vestibular/somatogyral.:Coriolis illusion.
   In the case of a thin oil film, a layer of oil sits on top of a layer of water. The oil may have an index of refraction near 1.5 and the water has an index of 1.33. As in the case of the soap bubble, the materials on either side of the oil film (air and water) both have refractive indices that are less than the index of the film. formula_21. There will be a phase shift upon reflection from the upper boundary because formula_22 but no shift upon reflection from the lower boundary because formula_23. The equations for interference will be the same.
   The autokinetic illusion occurs at night or in conditions with poor visual cues. This illusion gives the pilot the impression that a stationary object is moving in front of the airplane's path; it is caused by staring at a fixed single point of light (ground light or a star) in a totally dark and featureless background. The reason why this visual illusion occurs is because of very small movements of the eyes. In conditions with poor visual cues accompanied by a single source of light, these eye movements are interpreted by the brain as movement of the object being viewed. This illusion can cause a misperception that such a light is on a collision course with the aircraft.
   Section::::Pulse shaping.:Polarization.
   Section::::Range resolution (across track).
  
  The range resolution (the ability to separate the pixels of the image perpendicular to the direction of flight) of a SLAR depends on the length of the transmitted pulse. At the ground of Earth the range resolution has got an inverse relationship with the depression angle:
  
  The pulse width formula_3 is typically 0.4 … 1 µs, i.e. formula_7 = 8 … 200 m.
   Section::::Reception.
   Section::::Sears–Haack body.
  
  A superficially related concept is the Sears–Haack body, the shape of which allows minimum wave drag for a given length and a given volume. However, the Sears–Haack body shape is derived starting with the Prandtl–Glauert equation which governs small-disturbance supersonic flows. But this equation is not valid for transonic flows where the area rule applies. So although the Sears–Haack body shape, being smooth, will have favorable wave drag properties according to the area rule, it is not theoretically optimum.
  
  Section::::History.
  
  Section::::History.:Germany.
   Section::::Longitudinal modes.:Short period oscillations.
   The 3rd region surrounds the 2nd region and deflected waves captured by the receiver will have the same effect as a wave in the 1st region. That is, the sine wave will have shifted more than 270º but less than 450º (ideally it would be a 360º shift) and will therefore arrive at the receiver with the same shift as a signal might arrive from the 1st region. A wave deflected from this region has the potential to be shifted precisely one wavelength so that it is exactly in sync with the line-of-sight wave when it arrives at the receiving antenna.
   Section::::Vestibular/somatogyral.:Graveyard spin.
   Section::::Problem statement & basics.
  
  In a multipath system, the wireless channel is frequency dependent, time dependent, and position dependent. Therefore, the following parameters describe the channel:
  
  BULLET::::- Direction of departure (DOD)
  
  BULLET::::- Direction of arrival (DOA)
  
  BULLET::::- Time delay
  
  BULLET::::- Doppler shift
  
  BULLET::::- Complex polarimetric path weight matrix
   Section::::Vestibular/somatogyral.:Graveyard spiral.
   The pilot and observer sat very far forward in order for the pilot to have a reasonable field of downward vision for takeoff and landing and so that both he and the observer had a good field of view for spotting surface vessels even when in level flight.
   The marine navigation radar is non-coherent and is a typical example of an indirect wave sensor, because there is no direct relation between wave height and radar back-scatter modulation amplitude. An empirical method of wave spectrum scaling is normally employed. Marine navigation radar based wave sensors are excellent tools for wave direction measurements. A marine navigation radar may also be a tool for surface current measurements. Point measurements of the current vector as well as current maps up to a distance of a few km can be provided 
  
  (Gangeskar, 2002). 
   For incidence from water to air, or common glass to air, is not much different from . But is larger at smaller angles of incidence (Fig.12), and the amplitude may still be significant at distances of several times ; for example, because is just greater than 0.01, the evanescent wave amplitude within a distance of the interface is at least 1% of its value at the interface. Hence, speaking loosely, we tend to say that the evanescent wave amplitude is significant within "a few wavelengths" of the interface.
  
  Section::::Related phenomena.:Phase shifts.
   Section::::Theory.:Frequency domain.:Spatially encoded.
  