您的代码似乎存在以下问题:
- 在调用函数之前,您需要将
lat1
和lon1
转换为弧度。
- 您可能错误地缩放了
radialDistance
。
- 对浮点数进行相等性测试是危险的。即使在精确算术后相等的两个数字,在浮点算术后也可能不完全相等。因此,对于测试两个浮点数
x
和y
是否相等,abs(x-y) < threshold
比x == y
更安全。
- 我认为您想将
lat
和lon
从弧度转换为度数。
这是我使用Python实现您的代码:
from math import asin,cos,pi,sin
rEarth = 6371.01
epsilon = 0.000001
def deg2rad(angle):
return angle*pi/180
def rad2deg(angle):
return angle*180/pi
def pointRadialDistance(lat1, lon1, bearing, distance):
"""
Return final coordinates (lat2,lon2) [in degrees] given initial coordinates
(lat1,lon1) [in degrees] and a bearing [in degrees] and distance [in km]
"""
rlat1 = deg2rad(lat1)
rlon1 = deg2rad(lon1)
rbearing = deg2rad(bearing)
rdistance = distance / rEarth
rlat = asin( sin(rlat1) * cos(rdistance) + cos(rlat1) * sin(rdistance) * cos(rbearing) )
if cos(rlat) == 0 or abs(cos(rlat)) < epsilon:
rlon=rlon1
else:
rlon = ( (rlon1 - asin( sin(rbearing)* sin(rdistance) / cos(rlat) ) + pi ) % (2*pi) ) - pi
lat = rad2deg(rlat)
lon = rad2deg(rlon)
return (lat, lon)
def main():
print "lat1 \t lon1 \t\t bear \t dist \t\t lat2 \t\t lon2"
testcases = []
testcases.append((0,0,0,1))
testcases.append((0,0,90,1))
testcases.append((0,0,0,100))
testcases.append((0,0,90,100))
testcases.append((49.25705,-123.140259,225,1))
testcases.append((49.25705,-123.140259,225,100))
testcases.append((49.25705,-123.140259,225,1000))
for lat1, lon1, bear, dist in testcases:
(lat,lon) = pointRadialDistance(lat1,lon1,bear,dist)
print "%6.2f \t %6.2f \t %4.1f \t %6.1f \t %6.2f \t %6.2f" % (lat1,lon1,bear,dist,lat,lon)
if __name__ == "__main__":
main()
这是输出结果:
lat1 lon1 bear dist lat2 lon2
0.00 0.00 0.0 1.0 0.01 0.00
0.00 0.00 90.0 1.0 0.00 -0.01
0.00 0.00 0.0 100.0 0.90 0.00
0.00 0.00 90.0 100.0 0.00 -0.90
49.26 -123.14 225.0 1.0 49.25 -123.13
49.26 -123.14 225.0 100.0 48.62 -122.18
49.26 -123.14 225.0 1000.0 42.55 -114.51