Part 107 UAS pilot reported a near miss with a low flying helicopter.

Narrative

Was shooting film and photos for the local development going up to advertise the many different things the area has to offer. As a responsible drone pilot; I had planned the flight; looked to see if it was controlled airspace to which I found it was not. I remained under 400 feet at all times and did my best to keep VLOS.It was only 3 minutes into the flight around XA04 where I lost VLOS for approximately 30 seconds as I was transiting over the trees near telephone wires to the next shot when I paused to hover. I was transiting around 350 feet from the indicated launch location but as it was sloped terrain; I would presume it was more like 250 feet. I hovered for approximately 5 seconds when all of a sudden; a helicopter came up behind me and flew over me around 200-250 feet or lower. Shocked; I immediately brought my drone down which at the time was well clear of the incoming helicopter that continued to fly forward until it was lost in the horizon. Based on the terrain it was impossible to notice a manned aircraft at that low of an altitude till last second to which I yielded right of way as best as I could when I knew it was in the area. The helicopter came in and left so quickly I did not have enough time to catch the tail number; but I presume based on the unique ball like appearance on the tip of the front of the helicopter and low altitude/Large telephone wires running through the landscape that it was conducting inspections. Once again I immediately brought the drone down to the ground and ceased operations for the day. The biggest thing I believe that caused this incident was the fact that based on being unbelievably low and the terrain; simply listening was not good enough and the lack of scanning and keeping eyes on the drone compared to watching my screen was not sufficient. Another thing in Class G airspace; a copter coming this low is so rare in this area I was more relaxed than normal and not thinking of aircraft as much. Finally; my location where I launched and was watching the drone was not the best area to see beyond my drone and incoming aircraft until last second. These things I will take into consideration the next time I go out to fly in this location. I will also always from now and on bring a Visual observer to help me keep eyes on my aircraft at all times and look beyond and the airspace for such low incoming aircraft like such that was experienced that day.