I'm running a viewshed analysis is ArcMap 10.1, and I'm concerned about the results that I'm getting which if leading me to believe that my current understanding of viewshed variables may not be correct. Specifically, I'm concerned that I'm getting no viewshed values (GRIDCODE = 0) is areas were I'm fairly certain there should be a viewshed (based on personal knowledge).
The purpose of this viewshed analysis id to evaluate oceanfront views. I have a set of observation points that are centroid points to a home, and a lidar raster as my elevation input. The building footprint which the observation points rests in has been set to an elevation value of 0. Within the observation point file I have attribute fields for SPOT, AZIMUTH1, AZIMUTH2, RADIUS1, RADIUS2. I am currently not incorporating offset values.
I am understanding the SPOT value to be the height of the observer point measured from a height of 0. Is this correct? So, if I have the SPOT value listed as 13 and my map units are in feet, the observer height is being taken at 13 feet. Am I correct on this? If I am correct (which I'm fairly certain I am), is there something I may be missing that could be causing the off results I believe I'm getting?