Not to be rude, but the NXT sensor is actually a ultrasonic
sensor, as in it sends ultrasonic sound waves out as opposed to the infrasonic usually used be actual sonar sensors.
Yes, Ultrasonic sensors such as these do have problems getting a distance on a curved or angled surface, as it bounces the sound waves off at an angle, away from the sensor. This is problematic, because the sensor gauges distance by how long it takes the sound it shot out to bounce back to it. This is a problem with practically all Ultrasonic sensors, especially the LEGO ones. IR Light reflectance works better, but only at small distances. As you said, Laser Rangers are by far the best, but are usually too exspensive for the common person (and kinda dangerous). The kind of sonar on submarines and such have many, many transmitters and receivers, so it is virtually surrounded by sound. Also, things such a cloth tend to absorb sound waves, causing NONE to be returned.
So, have I enlightened you at all?
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