I am trying to implement a short python function to calculate the heading between two points. In other words if I am at point one, what heading relative to true north would I need to take to get to point two. I have used the following Python implementation which gives me essentially the same results.
from pyproj import Geod
lat1 = 42.73864
lon1 = 111.8052
lat2 = 43.24844
lon2 = 110.6083
geod = Geod(ellps='WGS84')
# This implements the highly accurate Vincenty method
bearing = geod.inv(lon1, lat1, lon2, lat2)[0]
# >>> 60.31358
I have also used the following code that uses a Haversine method
from math import degrees, radians, sin, cos, atan2
def bearing(lat1, lon1, lat2, lon2):
lat, lon1, lat2, lon2 = map(radians, [lat1, lon1, lat2, lon1])
dLon = lon2 - lon1
y = sin(dLon) * cos(lat2)
x = cos(lat1)*sin(lat2) - sin(lat1)*cos(lat2)*cos(dLon)
brng = degrees(atan2(y, x))
if brng < 0: brng += 360.0
return brng
With the same inputs from the previous implementation I get a result of 60.313 degrees, which matches the first implementation. However, when I use the Ruler function in google earth I get a result of 15.71 degrees. Furthermore when I activate the grid on google earth that shows the lines of longitude as a reference, 15.71 degrees makes far more sense. Why does the Google Earth implementation differ from the Python implementations?
the outputs of your geod code part are correct.
try to get behind it using easy examples (see below):
this means that there was probably a problem entering the coordinates into google earth or setting up the ruler but not in your code.
lat1 = 40
lon1 = 40
lat2 = 39
lon2 = 40
#output 180.0
or
#Kansas City:
lat1 = 39.099912
lon1 = -94.581213
#St Louis:
lat2 = 38.627089
lon2 = -90.200203
#output 96.4809
the second example can be confirmed on this page: https://www.igismap.com/formula-to-find-bearing-or-heading-angle-between-two-points-latitude-longitude/