Our TV news today said the cops have switched from radar to lidar because it is more accurate in fog. But isn't light absorbed by fog more than radar frequencies?
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Our TV news today said the cops have switched from radar to lidar because it is more accurate in fog.
All other things being equal in good visibility conditions lidar has a greater spacial accuracy than radar. Lidar also a better angular resolution which means that the lidar can differentiate between different vehicles better in heavy traffic.
So the accuracy part of tv news statement is correct.
However, the performance of lidar generally degrades a great deal in fog, rain and snow whereas that is much less so with radar. Thus the tv news statement is misleading with the reference to fog if you interpret the statement as meaning "lidar is generally better than radar in fog". There will be times when fog, snow and rain are present resulting in radar working and lidar not working.
Farcher
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LIDAR has usually greater flux than Radar because it is using a laser so the magnitude of the light is still high when received by the cars because the magnitude decreases as distance because of the inverse square law
Also transparency increases by frequency, so LiDar usually works in IR so it can go past the fog more easily. In dielectric mediums, there is a frequency known as the plasma resonant frequency, where a particular frequency is defined where an object becomes transparent, so higher frequencies have more chance of being transparent
Due to these factors we can measure the speed more easily in Lidar than radar, thus the speed mapping is more accurate.