UV mapping a proceduraly generated sphere in OpenGL - opengl

Question

I'm trying to UV a 2D texture on a globe. Here's a piece of code:
double
delta = 0.0, // angle of latitude
theta = 0.0, // angle of longitude
theta_interval = (2.0 * M_PI) / latitude, // angle of latitude
delta_interval = M_PI / longitude, // angle of longitude
u_lats = 0.0,
v_longs = 0.0,
u_lats_interval = 1.0 / latitude,
v_longs_interval = 1.0 / longitude;
for (int i = 0; i < longitude; ++i) {
for (int j = 0; j < latitude; ++j) {
double
x0 = calc_x0(radius, x, theta, delta),
y0 = calc_y0(radius, y, theta, delta),
z0 = calc_z0(radius, z, theta, delta),
u0 = u_lats,
v0 = v_longs + v_longs_interval,
x1 = calc_x1(radius, x, theta, delta, delta_interval),
y1 = calc_y1(radius, y, theta, delta, delta_interval),
z1 = calc_z1(radius, z, theta, delta, delta_interval),
u1 = u_lats + u_lats_interval,
v1 = v_longs + v_longs_interval,
x2 = calc_x2(radius, x, theta, theta_interval, delta, delta_interval),
y2 = calc_y2(radius, y, theta, delta, delta_interval),
z2 = calc_z2(radius, z, theta, theta_interval, delta, delta_interval),
u2 = u_lats + u_lats_interval,
v2 = v_longs,
x3 = calc_x3(radius, x, theta, theta_interval, delta),
y3 = calc_y3(radius, y, theta, theta_interval, delta),
z3 = calc_z3(radius, z, theta, theta_interval, delta),
u3 = u_lats,
v3 = v_longs;
theta += theta_interval;
u_lats += u_lats_interval;
}
v_longs += v_longs_interval;
theta = 0.0;
delta += delta_interval;
So the way I wanted to do it is to go through the first 'strap' on the texture and then move on to the next one but it doesn't look good. I'm starting to think that it might be something about the texture because if I render less sphere, for example only 3 iterations of latitude it looks different.
Here's some pictures:
Full globe:
Same globe with only three interations of latitude:
Does anyone have any idea what I'm doing wrong?