gps_time

This file will become your README and also the index of your documentation.

Breaking Change

Prior to version 3.x, gps_time did not include any timezone information, i.e. all datetimes used by gps_time were “naive”. This could lead to errors for versions of python that default to “aware” datetime objects. In version 3, gps_time is updated to function using aware datetime objects. If you pass gps_time a naive datetime, it will assume that it is meant to represent UTC time. As this was the expected behavior, there should be minimal impact, but this may result in errors to existing code bases.

Install

Installation can be achieved using pip, specifically

pip install gps_time

How to use

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)

2

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.

print(gps_time2)

Conversion

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 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())}")

Operators

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}")

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}")

License

Copyright (2020) The Aerospace Corporation. All Rights Reserved

The gps_time module releasded under the Apache2 license.

Open Source Licenses

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

Formatting

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.