thats the minimum size. you measured the closest thing to the camera. at that distance the definition would be better. now measure the building in the background that the "drone" is flying directly above.
the perspective in that photo means it could be minimum 1.83m long (doubtful its closer to the camera than the pole) or it could be kilometres long if its behind the building in the background by any substantial distance. The definition of the building is a touch better than the drone, but there appears to be a mist or fog distorting it. measuring the building would give another data point on its size if it were positioned somewhere in the middle of the pole and the building.