Regarding this site,..I will give you detailed information about this site.
1st.. The triangular positions of the old narra tree..If it is Equilateral dig the center of the triangle..If it is an isosceles then look for
the old narra tree or tree that similar to the leaves of the Narra tree forward..
2nd..That online Santol Tree,..based on your illustration their is an old santol Tree far from that online 4 Santol Tree,.Use a compass
from that 5th santol tree,..take a 90 deg. east 11 ft. forward and dig or go for trenching 4 to 6 ft. watchout for the marker,like Old bottle,
jar,a piece of metal,,etc.or rather a rock which could possibly the cap,..If you couldn't found anything..use this distance 11 or 22 meters from that 5th. old Santol tree..Go for trenching..Just an opinion
3rd..Regarding that old bamboo tree use that 1st. method it is almost the same..