Pyorbital

Geolocation in Pyorbital is affected by two main settings: Nadir Convention and Rotation Order. You can set these per function call or globally.

Available Options

Nadir Convention (defines 'down'):

• "legacy" (Default): The direction used in previous Pyorbital versions. Not re-orthogonalised against velocity.
• "geocentric": Straight at the center of the Earth. More accurate for most orbits.
• "geodetic": Along the ellipsoid normal.

Rotation Order (defines roll/pitch application):

• "legacy" (Default): Roll first, then pitch. The along-track component is compressed by cos(scan_angle).
• "pitch_first": Pitch first, then roll. The along-track component is independent of the scan angle.

Setting Conventions

1. Per function call (highest precedence):

from pyorbital.geoloc import geolocate
lons, lats, alts = geolocate(orbital, scan_geometry, times, 
                            nadir_convention="geocentric", 
                            rotation_order="pitch_first")

2. Process-wide via context manager:

import pyorbital
with pyorbital.config.set(nadir_convention="geocentric", rotation_order="pitch_first"):
    # All calls within this block use the new settings
    reprocess()

3. Via Environment Variables: Set PYORBITAL_NADIR_CONVENTION and PYORBITAL_ROTATION_ORDER in your shell.

IMPORTANT

To reproduce existing Pyorbital products exactly (e.g., for archive reprocessing), you must pin both to "legacy". Mixing "legacy" nadir with "pitch_first" rotation will not reproduce legacy output.

from pyorbital.geoloc import geolocate
lons, lats, alts = geolocate(orbital, scan_geometry, times,   # doctest: +SKIP
                              nadir_convention="geocentric",
                              rotation_order="pitch_first")

The pyorbital.orbital.Orbital class is used to compute a satellite's position, velocity, and geolocation at a specific time.

Using current TLEs (Internet-based)

By default, initializing Orbital with just a name will attempt to use the most recent TLEs from the internet.

from pyorbital.orbital import Orbital
import datetime as dt

# Initialize with satellite name
orb = Orbital("Suomi NPP")
now = dt.datetime.now(dt.timezone.utc)

# Get normalized position and velocity
pos, vel = orb.get_position(now)

# Get longitude, latitude, and altitude
lon, lat, alt = orb.get_lonlatalt(now)

Using specific TLE files for accuracy

For historical data or higher accuracy, provide a specific TLE file path to the Orbital constructor:

from pyorbital.orbital import Orbital
import datetime as dt

dtobj = dt.datetime(2015, 2, 7, 3, 0)
snpp = Orbital('Suomi NPP', tle_file='/path/to/tle/files/tle-20150207.txt')
lon, lat, alt = snpp.get_lonlatalt(dtobj)

from pyorbital.orbital import Orbital
import datetime as dt

# Use current TLEs from the internet:
orb = Orbital("Suomi NPP")
now = dt.datetime.now(dt.timezone.utc)

# Get normalized position and velocity of the satellite:
pos, vel = orb.get_position(now)

# Get longitude, latitude and altitude of the satellite:
lon, lat, alt = orb.get_lonlatalt(now)