Pyephem和pypredict/gppredict差异

Question

我正试图用pyephem来预测地面站的卫星通过率。然而，我得到的结果与我用pypredict和gppredict得到的结果大不相同。这是我写的代码。你知道吗

import ephem
import predict
import datetime as dt

def passes(station, satellite, start=None, duration=7):
    result = []
    if start is not None:
        station.date = ephem.date(start)
    end = ephem.date(station.date + duration)
    while station.date < end:
        t_aos, azr, t_max, elt, t_los, azs = station.next_pass(satellite)
        result.append({'aos': t_aos.datetime(), 'los': t_los.datetime()})
        station.date = t_los + ephem.second
    return result

tle = """ISS (ZARYA)
1 25544U 98067A   18274.33960752  .00001880  00000-0  36095-4 0  9991
2 25544  51.6416 209.7138 0003794 227.2741 275.6194 15.53757611135029"""

station = ephem.Observer()
station.lat = 20
station.long = 0
station.elev = 0

epoch = dt.datetime.utcnow()

for i in passes(station, ephem.readtle(*tle.split("\n")), epoch, 1):
    print(i['aos'], i['los'])

print("===============")
p = predict.transits(tle, (station.lat, -station.long, station.elev), (epoch - dt.datetime(1970,1,1)).total_seconds())
for i in range(1, 8):
        transit = p.next()
        print(dt.datetime.utcfromtimestamp(transit.start), dt.datetime.utcfromtimestamp(transit.end))

结果呢

(datetime.datetime(2018, 10, 1, 17, 4, 43, 552230), datetime.datetime(2018, 10, 1, 17, 11, 12, 744164))
(datetime.datetime(2018, 10, 1, 18, 39, 4, 59194), datetime.datetime(2018, 10, 1, 18, 47, 5, 185600))
(datetime.datetime(2018, 10, 1, 20, 14, 28, 126953), datetime.datetime(2018, 10, 1, 20, 22, 3, 101339))
(datetime.datetime(2018, 10, 1, 21, 51, 6, 130556), datetime.datetime(2018, 10, 1, 21, 55, 21, 829297))
(datetime.datetime(2018, 10, 2, 16, 13, 51, 767026), datetime.datetime(2018, 10, 2, 16, 19, 13, 556850))
===============
(datetime.datetime(2018, 10, 1, 13, 43, 6, 584816), datetime.datetime(2018, 10, 1, 13, 53, 21, 721679))
(datetime.datetime(2018, 10, 1, 15, 20, 13, 473098), datetime.datetime(2018, 10, 1, 15, 29, 13, 799433))
(datetime.datetime(2018, 10, 1, 21, 58, 25, 378030), datetime.datetime(2018, 10, 1, 22, 1, 54, 993473))
(datetime.datetime(2018, 10, 1, 23, 32, 5, 284033), datetime.datetime(2018, 10, 1, 23, 42, 37, 942300))
(datetime.datetime(2018, 10, 2, 1, 9, 49, 741668), datetime.datetime(2018, 10, 2, 1, 17, 12, 346213))
(datetime.datetime(2018, 10, 2, 12, 51, 59, 647871), datetime.datetime(2018, 10, 2, 13, 0, 57, 292565))
(datetime.datetime(2018, 10, 2, 14, 27, 39, 19468), datetime.datetime(2018, 10, 2, 14, 37, 48, 730909))

我对庇以弗有什么错？你知道吗

Answer 1

如果我没记错的话，在PyEphem中一个非常尴尬的接口决定是，作为浮点数提供的角度是弧度。（我开始写Skyfield的一个原因是为了有一个没有这个问题的天文学图书馆！）你知道吗

尝试：

station.lat = '20.0'