80,000 Li = 40,000 km, the equator is about 40,000 km long, and the earth turns once a day, so you can "sit on the ground and climb 80,000 Ali days, watch the astronomical phenomena and see thousands of rivers from a distance".
Longitude is arbitrary as long as latitude is zero or close to zero (e.g. east longitude 10 degree, north latitude 1 degree).