geodezyx’s Cookbook

Convert time

The geodezyx toolbox can handle a lot of time scales and time representations.

What we call scale is a physical definition: UTC, GPS Time, TAI…

What we call representation is the way the physical value is represented : Julian date, year/day of year, GPS week/day of week, ISO string…

The basic idea behind it is the conversion to and from the datetime objects of the Python’s datetime module.

The generic structure of the fuctions is conv.<input time scale/representation>2<output time scale/representation>.

Time conversion exemples

First of all:

import geodezyx.conv as conv                  # Import the conversion module
import datetime as dt

Get today as GPS Time (week/day of week)

now = dt.datetime.now()    ###  datetime.datetime(2021, 6, 18, 15, 53, 56, 245345)
gpstime = conv.dt2gpstime(now)

gpstime
Out: (2162, 5)

Convert year/day of year to Modified Julian Day

year,doy = (2021, 169)
epoch = conv.doy(year, doy)
mjd = conv.dt2MJD(epoch)

mjd
Out: 59383.0

Convert a SP3 name to decimal year

p = "/home/user/igs20726.sp3"

epoch = conv.sp3name2dt(p)
yeardec = conv.dt2year_decimal(epoch)

yeardec
Out: 2019.739611872146

It handles also RINEX names with conv.rinexname2dt(p_rinex) (old and new naming) (Documentation here: geodezyx.conv.conv_time.rinexname2dt())

Complete reference

All the module’s functionalites can be found here: geodezyx.conv.conv_time

Convert coordinates

The geodezyx toolbox can easily handle coordinate conversion in Geocentric (X,Y,Z), Geographic (latitude, longitude, height) and topocentric (East, North, Up).

Warning: This is considered as the “low-level” coordinate conversions. It does not deal with the different Reference Frame and their realisations (ITRFxx, ETRFxx…). This is managed by “high-level” functions in the reffram module.

These functions are optimized for arrays (multiple inputs) but can also handle scalars.

Coordinates conversion exemples

We consider as exemple the coordinates of the Helmertturm given in latitude, longitude, height from Wikipedia and the GNSS station POTS in Geocentric XYZ.

Helmertturm = np.array([52.380278, 13.065278,147.983])
POTS = np.array([3800689.6341,882077.3857,5028791.3179 ])

We can bring POTS in Geographic and the Helmertturm in Geocentric coordinates

POTS_geo = conv.XYZ2GEO(POTS[0],POTS[1],POTS[2])
POTS_geo = conv.XYZ2GEO(*POTS)

POTS_geo
Out: (52.37929737808202, 13.066091316954145, 144.41769897658378)

Helmertturm_xyz = conv.GEO2XYZ(Helmertturm[0],
                               Helmertturm[1],
                               Helmertturm[2])

Helmertturm_xyz = conv.GEO2XYZ(*Helmertturm)

Helmertturm_xyz
Out: (89.92804903383008, 14.005569048843014, -6356604.297220887)

We can also get the vector between POTS and the Helmertturm (i.e. the Helmertturm in the Topocentric frame centered on POTS)

conv.XYZ2ENU_2(Helmertturm[0], Helmertturm[1], Helmertturm[2],
               POTS[0],POTS[1],POTS[2])
Out: (array([0.88515353]), array([20735.55848087]), array([-6364723.46820732]))

Complete reference

All the module’s functionalites can be found here: geodezyx.conv.conv_coords

Helmert Transformations

Apply and estimate parameters for an ad-hoc Helmert Transformation

The functions geodezyx.reffram.geometry.helmert_trans_estim() and geodezyx.reffram.geometry.helmert_trans_apply() and offer an interface to estimate parameters and apply an Helmert transformation respectively.

Transform coordinates between two ITRF/ETRF

The functions geodezyx.reffram.geometry.itrf_helmert_get_parameters() and geodezyx.reffram.geometry.itrf_helmert_trans() offer an interface to get the transformation parameters between two ITREF/ETRF realization, and apply the corresponding Helmert transformation respectively.

Complete reference

All the module’s functionalites can be found here: geodezyx.reffram.geometry

Euler pole determination

The toolbox proposes tools to manipulate Euler rotation poles:

Complete reference

All the module’s functionalites can be found here: geodezyx.geodyn.euler_pole_calc

Read and import geodetic products

Main import functionalities

The toolbox mainly handles:

Complete reference

All the module’s functionalites can be found here: geodezyx.files_rw

Read and import geodetic time series

The toolbox is designed to import and pre-process a wide range of geodetic GNSS Time Series.

Read the dedicated Jupyter notebook stored in <...>/geodezyx/000_exemples/timeseries_reader

Complete reference

All the module’s functionalites can be found here: geodezyx.files_rw.read_coords_time_series

Read and import GNSS Sitelogs

You can easily import the content of the IGS’s GNSS Sitelogs (a.k.a Logsheets) in dedicated objects

Read the dedicated Jupyter notebook stored in <...>/geodezyx/000_exemples/logsheets_reader

Point and Click to detect offsets manually

The toolbox contains a tool to select manually the jumps in the Geodetic Time Series.

Based on matplotlib, you can “point and click” the discontinuities you detected visually with your mouse.

Plot first your data (in a theoretical DataFrame DF)

fig,(axn,axe,axu) = plt.subplots(3,1)
axn.plot(DF["t"],DF["n"])
axe.plot(DF["t"],DF["e"])
axu.plot(DF["t"],DF["u"])

Then, create the Point and Click object

PnC = gcls.point_n_click_plot()
multi , cid = PnC(fig=fig)

The selected jumps/offsets are stored in a list attribute of the Point and Click object

PnC.selectedX

Read the dedicated script stored in <...>/geodezyx/000_exemples/logsheets_reader. More details in the class documentation : geodezyx.time_series.ts_class.point_n_click_plot

Statistics and plots for orbit and clock comparisons

TBC