Its time for me to mention something very important to everybody,
There is no possible way that anybody can see any images on rocks with weeds laying all over them, or with blurry photos.
If there are weeds get rid of them around the marker, if there are tree limbs get rid of them especially if they are obstructing your alignments.
Take more than one picture of a marker in case you get a blurry shot on one or two photos, and try to do this at different distances, I take 3-5 pictures at different zoom distances of each marker, then when I get home I find the one that looks the best on the computer, and People, Cell Phones are not very good cameras.