Latitude of observer pin may not coincide with grid cell

[lemmingapex]

When the viewshed is run, the observer's cell is colored in black. For large viewsheds, the latitude of observer pin may not coincide with this black grid cell. In the northern hemisphere, the grid cell is north of the pin. This may have to do with the centroid of the area calculation for the UIimage. I'm not sure if the curvature of the earth or map projection need to be accounted for.