-- TM grid to Lat Long

e={413281.966160,387453.412881}
n={5834950.555005,5826193.965008}
zn={31, 31}


include "WGS84data.txt"

k= kx:=(n-n0)/a1+k0, k3:=0, k4:=0, am:=0, del:=1, (k3:=kx-k0, k4:=kx+k0, am:=
((1+n1+1.25*n1^2+1.25*n1^3)*k3-(3*n1+3*n1^2+21/8*n1^3)*sin(k3)*cos(k4)+
(15/8*n1^2+15/8*n1^3)*sin(2*k3)*cos(2*k4)-35/24*n1^3*sin(3*k3)*cos(3*k4))*b1,
del:=n-n0-am, kx:=kx+del/a1) while del>0.0001, kx

v=a1/sqrt(1-e2*sin(k)^2)
r=v*(1-e2)/(1-e2*sin(k)^2)
h2=v/r-1

y1=e-e0
lat=k-y1^2*tan(k)/(2*r*v)+y1^4*tan(k)/(24*r*v^3)*(5+3*tan(k)^2+h2-9*tan(k)^2*h2)-
y1^6*tan(k)/(720*r*v^5)*(61+90*tan(k)^2+45*tan(k)^4)

lon=l0+y1/(v*cos(k))-y1^3/(cos(k)*6*v^3)*(v/r+2*tan(k)^2)+y1^5/(cos(k)*120*v^5)*
(5+28*tan(k)^2+24*tan(k)^4)-y1^7/(cos(k)*5040*v^7)*(61+662*tan(k)^2+1320*tan(k)^4+
720*tan(k)^6)

latd=lat*180/pi
lond=lon*180/pi

latd:{102.227998152,102.149467608}
lond:{-2.561811920,-1.465917266}