Distance value for hotspots

Hi, I saw a similar question on other thread however think this situation is slightly different. Ok so let's supose my panorama is geotagged, so it's center would be at an specific coordinate, and it will be always initially loaded pointing at north. I got some calculations in order to create hotspots pointing to other geotagged scenes in my viewer. It works pretty well... but then the user is able to add hotspots inside the viewer, So the question is as follows. Is there some kind of variable that I could use in order to recreate distance??. For example my panorama is located at coordinate -0.12232,1.445433. Now I added a hotspot inside the viewer and want to assign it also a coordinate, that would be the center plus some meters depending on the angle that's currently pointing the user... But is there some kind of zoom?? in the viewer that I could use to calculate or relate meters or distance to the coordinates? Thanks a lot.