I am using camera traps a with passive infrared sensor for my research and last week I decided to test their detection zones. I expected to find detection zone looking like this:
with a certain angle and range in which the sensor would operate, but instead I kept finding that the camera would only detect within a more 'rounded' zone:
Is this normal for passive infrared sensors? Or is it a consistent measurement error? Someone mentioned directivity to me but I have not been able to understand how that applies here. I hope this is the right place to ask, otherwise please point me in the right direction.