Sad to say....classical and predictable survey accident. Single engine piston, probably 1st line of the day flying heavy, high alt and low to the ground with limited viz into the sun with mountainous terrain to deal with.
8 or 9 yrs ago a similar accident in Namibia claimed the lives of 2 Canadians doing exactly the same in a multi piston.
Interested to find out whether these guys were here to do this on a temporary basis with little or no survey experience in their past flying career.
Should not have happened........
My condolences to all family and friends.