Closes gh-31 Fix decimal to degree, minute, second conversion by making seconds more precice and supporting negative values

elodie/geolocation.py

@@ -12,13 +12,11 @@ from elodie import constants
 
 class Fraction(fractions.Fraction):
     """Only create Fractions from floats.
-
     >>> Fraction(0.3)
     Fraction(3, 10)
     >>> Fraction(1.1)
     Fraction(11, 10)
     """
-
     def __new__(cls, value, ignore=None):
         """Should be compatible with Python 2.6, though untested."""
         return fractions.Fraction.from_float(value).limit_denominator(99999)
@@ -47,28 +45,20 @@ def coordinates_by_name(name):
     return None
 
 def decimal_to_dms(decimal):
-    """Convert decimal degrees into degrees, minutes, seconds.
+    # if decimal is negative we need to make the degrees and minutes negative also
+    sign = 1
+    if(decimal < 0):
+        sign = -1
+
 
-    >>> decimal_to_dms(50.445891)
-    [Fraction(50, 1), Fraction(26, 1), Fraction(113019, 2500)]
-    >>> decimal_to_dms(-125.976893)
-    [Fraction(125, 1), Fraction(58, 1), Fraction(92037, 2500)]
-    """
-    # @TODO figure out a better and more proper way to do seconds
     degrees = int(decimal)
     subminutes = abs((decimal - int(decimal)) * 60)
-    minutes = int(subminutes)
+    minutes = int(subminutes) * sign
-    subseconds = abs((subminutes - int(subminutes)) * 60)
+    subseconds = abs((subminutes - int(subminutes)) * 60) * sign
-    return (pyexiv2.Rational(degrees, 1), pyexiv2.Rational(minutes, 1), pyexiv2.Rational(subseconds, 1))
+    subseconds_fraction = Fraction(subseconds)
+    return (pyexiv2.Rational(degrees, 1), pyexiv2.Rational(minutes, 1), pyexiv2.Rational(subseconds_fraction.numerator, subseconds_fraction.denominator))
 
 def dms_to_decimal(degrees, minutes, seconds, sign=' '):
-    """Convert degrees, minutes, seconds into decimal degrees.
-
-    >>> dms_to_decimal(10, 10, 10)
-    10.169444444444444
-    >>> dms_to_decimal(8, 9, 10, 'S')
-    -8.152777777777779
-    """
     return (-1 if sign[0] in 'SWsw' else 1) * (
         float(degrees)        +
         float(minutes) / 60   +

elodie/tests/geolocation_test.py

@@ -1,8 +1,8 @@
 # Project imports
 import os
-import sys
+import random
-
 import re
+import sys
 
 sys.path.insert(0, os.path.abspath(os.path.dirname(os.path.dirname(os.path.dirname(os.path.realpath(__file__))))))
 
@@ -12,9 +12,16 @@ from elodie import geolocation
 os.environ['TZ'] = 'GMT'
 
 def test_decimal_to_dms():
-    target_decimal_value = 37.383336725
+
+    for x in range(0, 1000):
+        target_decimal_value = random.uniform(0.0, 180.0)
+        if(x % 2 == 1):
+            target_decimal_value = target_decimal_value * -1
     
         dms = geolocation.decimal_to_dms(target_decimal_value)
         check_value = dms[0].to_float() + dms[1].to_float() / 60 + dms[2].to_float() / 3600
 
+        target_decimal_value = round(target_decimal_value, 8)
+        check_value = round(check_value, 8)
+
         assert target_decimal_value == check_value, '%s does not match %s' % (check_value, target_decimal_value)