How to determine the presence of people within a radius of 300 meters?

Question

Algorithms

Let's say I'm in a rural area, a village, roughly speaking, how can I determine with the help of those means that there are people (animals too) within a radius of 300 meters from me or not and mark them on a map of the area?
PS The terrain is not a field, so purely visual recognition does not roll, there may be bushes and trees behind which you can not see.
PPS The thermal imager does not roll during the day either.
And yes, of course, the most low-budget options are of interest.

Answer 1

Just like a person does: visually and acoustically (including echolocation) + NS.

Answer 2

From the air it is possible with the help of image recognition from the UAV, provided that the objects are not masked.

Answer 3

Just in terms of sound