How to count humans in open space using sensors?

I would assume that all ground staff require some form of ID. Have you considered adapting that ID to allow for location detection.

Of course we can consider the ID card but six months ago one passenger travelled in the retractable landing gear from London to Canada and while the landing gear came down at 3000 ft that person had fallen down and died. Even we have lot of security measures we are seeing these sort of accidents.So a sensor can help us in this situation( I forgot the exact date ) so we are trying this at a basic level if this clicked we shall develop it further.

Based on what you've said, I would suggest a multi-layered approach as I doubt a single system could capture all use cases.

For example, if you create an ID badge with active beacon for location detection then this system can be synced in with a system that detect movement, on the assumption that everything is connected wirelessly to sync ID versus object detection etc.

As you are wanting to monitor areas under an aircraft, I assume then that you are height restricted, in terms of where you can place the sensor.

As such, there are LiDar sensors such as this one, for example, that might work as could be used to detect objects up to 40 meters away. Here is another, that measures up to 22 meters away. These could be used to create "no go" areas underneath the aircraft engine.

Otherwise looking at Radar/Microwave/PIR sensors. There are plenty of off the shelf options around that can detect up to 15m away and a few that could detect up to 30m away.

Cameras may not work looking horizontally for image capture in this case.

Based on what you've said, I would suggest a multi-layered approach as I doubt a single system could capture all use cases.

For example, if you create an ID badge with active beacon for location detection then this system can be synced in with a system that detect movement, on the assumption that everything is connected wirelessly to sync ID versus object detection etc.

As you are wanting to monitor areas under an aircraft, I assume then that you are height restricted, in terms of where you can place the sensor.

As such, there are LiDar sensors such as this one, for example, that might work as could be used to detect objects up to 40 meters away. Here is another, that measures up to 22 meters away. These could be used to create "no go" areas underneath the aircraft engine.

Otherwise looking at Radar/Microwave/PIR sensors. There are plenty of off the shelf options around that can detect up to 15m away and a few that could detect up to 30m away.

Cameras may not work looking horizontally for image capture in this case.