▲ | mxfh 4 days ago | |
Except the helix curve shown in OP is NOT a loxodrome or rhumb line. It has equal spacing on the surface between lines, a loxodrome can't have that property since by definition it must cross the meridians at the same angle at all times. That means it always gets denser near the poles. --- Start with the curve: x = 10 · cos(π·t/2) · sin(0.02·π·t) y = 10 · sin(π·t/2) · sin(0.02·π·t) z = 10 · cos(0.02·π·t) Convert to spherical coordinates (radius R=10): λ(t) = π/2 · t (longitude) φ(t) = π/2 - 0.02·π·t (latitude) Compute derivative d(λ)/d(φ): d(λ)/dt = π/2 d(φ)/dt = -0.02·π d(λ)/d(φ) = (π/2)/(-0.02·π) = -25 (constant) A true rhumb line must satisfy: d(λ)/d(φ) = tan(α) · sec(φ) which depends on latitude φ. Since φ(t) changes, sec(φ) changes, so no fixed α can satisfy this. Conclusion: the curve is not a rhumb line. this is how one should look for varying intersection angles: | ||
▲ | srean 3 days ago | parent [-] | |
Indeed. It is one of the many well known spherical spirals / seiffert spirals. |