I am trying to run a viewshed analysis and I've downloaded DEM data from the UK ordnance survey (Landform-panorama). Since the data is in ASCII format I have created a seamless raster mosaic (and used the projected coordinate system - British National Grid). Now I am trying to display a point layer, with lat/lon coordinates of about 10 sites on top of the DEM raster layer. I have been told that both the raster layer and the point layer needs to have the same coordinate system, but when I use the projected coordinate system on the point layer, my points do not show up. However, if I use the geographic coordinate system on the point layer then the site locations pop up:
I was wondering whether any one could let me know if this is alright for a viewshed analysis? if not whether anyone could explain in layman's terms what I need to do in order to fix this issue. As always any advice would be greatly appreciated!