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Radar will not detect bodies of water on the ground (lakes, rivers etc) as the beam is reflected from the flat surface away from the
aircraft. Terrain is detected as is scatters the beam, and the back scatter can be seen on the display
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You're assuming that the water is flat. If there are ripples on the order of the radar wavelength (typically centimetre or millimetre) then you will get backscatter from those. What wavelength is weather radar using??
Interestingly (at least, to me) Radar makes a very good way to detect ships, especially when the seastate is calm, as the wake is rougher than the rest of the sea surface. You get a nice bright trail leading straight to your target. Take a look at
http://www.lpi.usra.edu/images/soce/soce_S10.gif
for example. That one is a photo, but you get just the same effects in RADARSAT images - I just dont have any to show. There's a shuttle-based SAR image of the gulf stream, however, just to show that radar can detect bodies of water on the ground pretty darn well
http://www.lpi.usra.edu/images/soce/soce_S04.gif
Cheers,
Evo.
[This message has been edited by Evo7 (edited 04 June 2001).]