Can someone please tell the height of each different colour .....
B21 = 5, L21 = 4, BB21 = 3, FF21 = 2, GG20 = 1, JJ19 = 0 (i.e. ground), OO20 = -1
2) Do you need to be adjacent to the river to see "into" the river in a G hex?
This will follow the same rules as any LOS across a crest line, so...