cylindrical equal-area projection

[haroim]

I have looked into it and i get out the following:

If i want to make a projection i will need for each (x,y) an altitude. I can find the altitude in a (lon,lat) form. So to get the altitude of (x,y) i will need to know the (lon,lat) of (x,y).

(x,y)=(lon,lat)

x = 2*pi*cos(theta) * (lon + 180)/360
lon = (x*360)/(2*pi*cos(theta))-180

y = R*sin(lat)/cos(phi)
lat=invsin(cos(phi)*y/R)

so (x,y)=(lon,lat)=( (x*360)/(2*pi*cos(theta))-180, invsin(cos(phi)*y/R)) )

so i should be able to calculate the altitude of (x,y) by taking the altitude of ( (x*360)/(2*pi*cos(theta))-180, invsin(cos(phi)*y/R)) ).

is this correct? And what is phi? Is it the standard latitude, and what number should i enter?