Table of Contents
Introduction
In this blog post we will present a function to convert from decimal degrees (dd) to degree-minutes-seconds (dms) using Python Programming. This conversion can come in handy when you need dms for report writing for example.
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Using Python to Convert from Decimal Degrees to Degrees-Minutes-Seconds
The code below uses the math module from the Standard Python Library to convert from dd to dms.
import math
def dd2dms(longitude, latitude):
## math.modf() splits whole number and decimal into tuple
## eg 53.3478 becomes (0.3478, 53)
split_degx = math.modf(longitude)
## the whole number [index 1] is the degrees
degrees_x = int(split_degx[1])
## multiply the decimal part by 60: 0.3478 * 60 = 20.868
## split the whole number part of the total as the minutes: 20
## abs() absoulte value - no negative
minutes_x = abs(int(math.modf(split_degx[0] * 60)[1]))
## multiply the decimal part of the split above by 60 to get the seconds
## 0.868 x 60 = 52.08, round excess decimal places to 2 places
## abs() absoulte value - no negative
seconds_x = abs(round(math.modf(split_degx[0] * 60)[0] * 60,2))
## repeat for latitude
split_degy = math.modf(latitude)
degrees_y = int(split_degy[1])
minutes_y = abs(int(math.modf(split_degy[0] * 60)[1]))
seconds_y = abs(round(math.modf(split_degy[0] * 60)[0] * 60,2))
## account for E/W & N/S
if degrees_x < 0:
EorW = "W"
else:
EorW = "E"
if degrees_y < 0:
NorS = "S"
else:
NorS = "N"
## abs() remove negative from degrees, was only needed for if-else above
print("\t" + str(abs(degrees_x)) + u"\u00b0 " + str(minutes_x) + "' " + str(seconds_x) + "\" " + EorW)
print("\t" + str(abs(degrees_y)) + u"\u00b0 " + str(minutes_y) + "' " + str(seconds_y) + "\" " + NorS)
The Conversion in Action
## some coords of cities
coords = [["Dublin", -6.2597, 53.3478],["Paris", 2.3508, 48.8567],["Sydney", 151.2094, -33.8650]]
## run dd2dms()
for city,x,y in coords:
print(f"{city}:")
dd2dms(x, y)
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