Hello Orekit Community!

I’ve been playing around with `measurements.generation`

methods recently. I’ve generated measurements using `PVBuilder`

and compared my syntetically generated PV with TLE generated PV. And results are quite nice.

Then I used similar logic and methods to create `AngularAzElBuilder`

(and `AngularRaDecBuilder`

). However the results are somewhat odd, however I adjust my parameters, syntetic AzEl data deviates from TLE generated AzEl data significantly, which indicates an error in my implementation.

Here is the code snipped I’ve been using to generate AzEl data:

```
sigma = 1e-5 # Standart deviation
azElError = [sigma, sigma]
azElBaseWeight = [1.0, 1.0]
covariance = MatrixUtils.createRealDiagonalMatrix([sigma**2, # Covariance matrix
sigma**2,
sigma**2,
sigma**2,
sigma**2,
sigma**2])
# Create random correlated vector
random_vector = CorrelatedRandomVectorGenerator(covariance, 1.0e-10,
GaussianRandomGenerator(MersenneTwister()))
# Make the generator
generator = Generator()
obs_sat = ObservableSatellite(0)
generator.addPropagator(propagator)
azelBuilder = AngularAzElBuilder(random_vector, ground_station, azElError, azElBaseWeight, obs_sat)
generator.addScheduler(ContinuousScheduler(azelBuilder, FixedStepSelector(dt, TimeScalesFactory.getUTC())))
# Measurement data is generated
measurement_data = generator.generate(date_start, date_end)
AZEL_generated_eci_df = pd.DataFrame()
for measurements in measurement_data:
castedMeasurements = AngularAzEl.cast_(measurements) # Casting measurements into Az-El
AZEL_generated_eci_df = pd.concat([AZEL_generated_eci_df, orekitAZEL2dataframe(castedMeasurements, castedMeasurements.getDate())])
AZEL_generated_eci_df.reset_index(drop=True, inplace=True)
print('\033[1m'+'AZEL_generated_eci_df '+'\033[0m')
print(AZEL_generated_eci_df.to_string())
```

Then I have the following to generate AzEl from the TLE:

```
AZEL_tle_eci_df = pd.DataFrame()
date_current = AZEL_generated_eci_df['DateTimeUTC'][0]
propagator.propagate(date_current)
while date_current.compareTo(date_end) <= 0:
datetime_current = absolutedate_to_datetime(date_current)
PV_tle_eci = propagator.getPVCoordinates(date_current, ECI)
pos = PV_tle_eci.getPosition()
az, el, r = cartesian_to_azel(pos.getX(), pos.getY(), pos.getZ())
az = radians(az)
el = radians(el)
azel = AngularAzEl(ground_station, date_current, [az, el], azElError, azElBaseWeight, obs_sat)
AZEL_tle_eci_df = pd.concat([AZEL_tle_eci_df, orekitAZEL2dataframe(azel, datetime_current)])
date_current = date_current.shiftedBy(dt)
AZEL_tle_eci_df.reset_index(drop=True, inplace=True)
print('\033[1m'+'AZEL_tle_eci_df '+'\033[0m')
display(AZEL_tle_eci_df)
```

I am also using a definition which transforms PV to AzEl. I am attaching the code to the topic (sorry if code is a bit messy )

Notice once again that the procedure I implement here is almost same with the one I use in `PVBuilder`

. Should I use something different or am I missing something?

Any discussion is very well appreciated

Have a great day!

Kind regards,

Baris

AZ-EL_Measurement_Generation.ipynb (4.0 MB)