In what scenario would LIDAR not be effective in measuring speed?

LIDAR, which stands for Light Detection and Ranging, relies on the emission of laser beams to measure distances and speed. For LIDAR to effectively measure speed, it must have a clear line of sight to the target. If there is no line of sight, the LIDAR cannot detect or measure the returning laser signals from the object. This absence of visibility can occur in situations where obstacles, weather conditions, or other factors obstruct the LIDAR beam, preventing the accurate data transmission needed for speed calculation.

In contrast, the other scenarios mentioned can still allow for LIDAR to function effectively as long as proper conditions are met. For instance, moving fast does not hinder LIDAR's ability to measure speed; in fact, it is designed to do just that. Proper calibration is crucial for accuracy, and standing still does not impede LIDAR measurement as it can still measure speed relative to other moving objects. Therefore, the lack of line of sight is the only scenario where LIDAR would be ineffective in measuring speed.