The loop vehicle detector is a traditional traffic detector. Its working principle is to embed induction coil on the road, and the induction coil is linked with the vehicle detector. 
When the vehicle passes through the coil, due to the change of coil inductance, the change of vehicle passing state is detected. At the same time, the state signal is transmitted 
to the vehicle detector for collection and calculation.

Advantage：Compared with other detectors, the coil vehicle detector has the advantages of low cost, high reliability, high detection accuracy and all-weather operation. It is the most widely used vehicle detector at present.

Disadvantage: According to the construction requirements of the ring coil, the first installation needs to cut the road surface, which causes damage to the road surface due to high construction cost; The detection coil is easy 
to sink and crack on the road surface which cause  False positive; Due to the limitation of its own measurement principle, when the traffic flow is congested and the vehicle spacing is small, the measurement accuracy will be greatly reduced;

GDC1000 3D Camera is G-TEK sensor new 3D vision sensor, it is designed especially for vehicle detection at barrier gate system. It can replace the loop coin and detector and easy the site installation.

GDC1000 measures distance at TOF (time of flight) principle basis. GDC1000 emits modulated laser (invisible) pulse continuously and when the light pulse encounters an object, it will be reflected and received by GDC1000 again. By calculating the phase difference and time difference of the light pulse transmitting and receiving, the distance between the measured object and the camera will be acquired.

More information about GDC1000 by  http://www.gteksensor.com/product/82.html