A D sin D A E
D E = ———————
sin A E D
or log D E = log A D + L sin D A E-L sin A E D.
From station F, E and G are visible, but the landmark D cannot be seen; therefore, as the latter can be seen from G, it will be necessary to fix the position of G first. Then,
sin E G D: D E :: sin E D G : E G,
D E sin E D G
or EG= ———————-
sin E G D
Now, sin E F G: E G :: sin F E G : F G
E G sin F E G
F G = ——————-
sin E F G
thus allowing the position of F to be fixed, and then
sin F H G : F G :: sin F G H : F H
F G sin F G H
F H= ——————-
sin F H G