I think there might be a problem with a DEM I'm using to ran a viewshed analysis of a coastal area (88mt above sea level).
I've ran the tool twice, analysing the same area except the second analysis covers up a larger area. My results on the second analysis are really confusing: the west, north-west quadrant is either skipped or deemed not visible. I think this is incorrect because: a) I've been to the site, b) on the previous analysis, the area is indeed visible. I set up an observer at 16mt above the ground and only then I'm getting the area visible again.
Any ideas on what could be wrong, and how could I fix this? I'm attaching images of my first two results. For the two analyses I ran, I clipped the same source DEM.