Tools for handling time related to GPS

This module is used to represent GPS time and provide tools for handling it. The tools developed here were originally made in pure python, but were later converted to jupyter notebooks using nbdev. The goal is to provide an absolute time representation for python that is easer to use for scientific computing and with higher resolution than the built-in datetime.

Installation can be achieved using pip, specifically

pip install gps-time

This module is relatively straightfoward to use. The GPSTime objects are generated (using arbitrary numbers) by

gps_time1 = GPSTime(week_number=1872, time_of_week=3324.654324324234324)
gps_time2 = GPSTime(week_number=1875, time_of_week=9890874.32)

Notice that the time of week for gps_time2 is longer than a week. The GPSTime object will automatically adjust the week number and time of week to reasonable values.

gps_time2

GPSTime(week_number=1891, time_of_week=214074.3200000003)

The GPSTime objects can also created from datetime.datetime objects

gps_time3 = GPSTime.from_datetime(datetime.datetime(2017, 9, 2, 13, 23, 12, 211423))
print(gps_time3)

GPSTime(week_number=1964, time_of_week=566592.211423)

GPSTime can likewise be converted to datetime.datetime object. However, one must be careful because datetime.datetime objects only preserve microsecond resolution. Converting from GPSTime to datetime.datetime can lose information. The opposite conversion does not lose information.

print(f"GPS Time: {gps_time1}")
print(f"Datetime: {gps_time1.to_datetime()}")
print("")
print(f"Lost Precision: {gps_time1 - GPSTime.from_datetime(gps_time1.to_datetime())}")

GPS Time: GPSTime(week_number=1872, time_of_week=3324.6543243242345)
Datetime: 2015-11-22 00:55:24.654324

Lost Precision: 3.2423440643469803e-07

GPSTime has comparison operators defined (equality, less than, etc.). It also has addition and subtraction defined. In general, one can add/subtract either floats or other GPSTimes.

For floats, it is interpreted as a time shift in seconds (forward for addition, backward for subtraction). This operation accounts for the time of week. In-place addition and subtraction, i.e. the += and -= operators are supported for floats.

time_shift_seconds = 23431123.3243

print(f"Addition (float):    {gps_time2 + time_shift_seconds}")
print(f"Subtraction (float): {gps_time2 - time_shift_seconds}")

Addition (float):    GPSTime(week_number=1930, time_of_week=57997.64429999888)
Subtraction (float): GPSTime(week_number=1852, time_of_week=370150.9957000017)

Alternatively, addition and subtraction can be done using two GPSTime objects. Subtraction finds the time difference in seconds (as a float). Addition essentially sums the week numbers and times of week. Notice that in-place addition and subtraction are not supported for two GPSTime objects.

print(f"Addition (GPSTime):    {gps_time2 + gps_time1}")
print(f"Subtraction (GPSTime): {gps_time2 - gps_time1}")

Addition (GPSTime):    GPSTime(week_number=3763, time_of_week=217398.97432432455)
Subtraction (GPSTime): 11701949.665675675

Copyright (2020) The Aerospace Corporation. All Rights Reserved

The gps_time module releasded under the Apache2 license.

This module is built on the nbdev template, which is used under the Apache2 license.

As much as possible for jupyter notebooks, the black formatting standard will be used. To apply black to jupyter notebooks, the jupyter-black extension can be used.