How Can I Accurately Calculate GPS Distance and Bearing Using the Haversine Formula?

Haversine Formula for GPS Calculations: Distance and Bearing

Problem:

Calculating the distance and bearing between two GPS points often involves utilizing the Haversine distance formula. However, issues can arise when obtaining the correct bearing, particularly if negative values are produced.

Solution:

To calculate the distance, the Haversine formula can be employed:

from math import radians, cos, sin, asin, sqrt

def haversine(lon1, lat1, lon2, lat2):
    """
    Calculate the great circle distance in kilometers between two points 
    on the earth (specified in decimal degrees)
    """
    # convert decimal degrees to radians 
    lon1, lat1, lon2, lat2 = map(radians, [lon1, lat1, lon2, lat2])

    # haversine formula 
    dlon = lon2 - lon1 
    dlat = lat2 - lat1 
    a = sin(dlat/2)**2 + cos(lat1) * cos(lat2) * sin(dlon/2)**2
    c = 2 * asin(sqrt(a)) 
    r = 6371 # Radius of earth in kilometers. Use 3956 for miles. Determines return value units.
    return c * r

To determine the bearing, adjust the Bearing variable as follows:

Bearing = atan2(sin(lon2-lon1)*cos(lat2), cos(lat1)*sin(lat2) - sin(lat1)*cos(lat2)*cos(lon2-lon1))
Bearing = degrees(Bearing)

This modification ensures that the bearing lies between 0 and 360 degrees.

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