Not all the aircraft over Syria belong to the Syrian government or the American led anti-ISIL (the Islamic State in Iraq and the Levant) coalition. A growing number of rebel groups, many of them Islamic terrorists, are using Chinese made quadcopters. The most popular is the Chinese Phantom quadcopter. The latest model, the Phantom 3, weighs 3.9 kg (8.6 pounds) can stay in the air about 20 minutes per flight and can go up to 2,000 meters from the operator. The operator can see (at 720p) what is under the Phantom using a small display and capture a higher resolution video (“2.7k” or 1080p) on a 16 GB micro memory card on the UAV. The Phantom 3 costs a thousand dollars and is widely available. It is easy to operate and has flight control software that makes it easy to operate and keeps the video image stable. You can equip these with a night vision camera. Max altitude is over 500 meters (1,600 feet) but most Phantoms operate lower down because getting to higher altitude takes time.
There are cheaper quadcopters and fixed wing UAVs and more expensive ($10,000 or more) ones. But for the needs of irregular forces in a chaotic combat zone relative cheap ones like Phantom get the job done. The sweet spot appears to be the thousand dollar Phantom 3 or similar models. It gets the job done, is easy to operate and you can afford to lose a few.