How can I estimate the distance to an object in the field. I would like to know how to determine distance for long and short distance objects.

I was looking at my map last trip and trying to determine my location by triangulation, but all the peaks in the distance were so far away that they sorta blended and I could not tell what was what. Closer in there was a set of peaks and I could not determine if they were the first set on my map or the second set on my map. This is sort of new to me, but I find it very challenging. I have been googling with the intent of finding some source of info on distance determination, but I can't find much. I did find the online Army field manual and it was pretty cool.