Rhumb destinations do not wrap angles after the first pole intersection #1152
Description
Given that a rhumb line has finite length to a given pole, and that RhumbDestination appears to wrap correctly in one direction, one would expect that latitude would be bounded to +/-90 and longitude to +/-180 as the path length increased. Instead, we see the following:
Here is a rust program that dumps the data:
use geo::{Point, RhumbDestination};
use std::fs::OpenOptions;
use std::io::{BufWriter, Error, Write};
fn main() -> Result<(), Error> {
let write = OpenOptions::new().write(true).create(true).open("./rhumb.csv");
let mut writer = BufWriter::new(write.unwrap());
let origin = Point::new(0.0, 0.0);
for i in 0..1000000 {
let dist = 100.0 * (i as f64);
let dest = origin.rhumb_destination(45.0, dist);
let lon = dest.x();
let lat = dest.y();
writer.write(format!("{dist:.16},{lon:.16},{lat:.16}\n").as_bytes())?;
}
Ok(())
}
and some python code to load and plot:
import pandas as pd
from matplotlib import pyplot as plt
df = pd.read_csv('rhumb.csv', header=None)
fig, ax = plt.subplots(2, 1, constrained_layout=True)
ax[0].plot(df[0], df[1])
ax[1].plot(df[0], df[2])
ax[0].set_title('Lon vs Dist')
ax[1].set_title('Lat vs Dist')
The expected fix would be that latitude would be clamped, either by taking the modulo of the path length from pole to pole, or empirically.