def compute_lonlat(self, width, utcs=None, clock_drift_adjust=True):
"""Compute lat/lon coordinates.
Args:
width: Number of coordinates per scanlines
utcs: Scanline timestamps
clock_drift_adjust: If True, adjust clock drift.
"""
tle1, tle2 = self.get_tle_lines()
scan_points = np.arange(3.5, 2048, 5)
if utcs is None:
utcs = self.get_times()
# adjusting clock for drift
tic = datetime.datetime.now()
if clock_drift_adjust:
from pygac.clock_offsets_converter import get_offsets
try:
offset_times, clock_error = get_offsets(self.spacecraft_name)
except KeyError:
LOG.info("No clock drift info available for %s",
self.spacecraft_name)
else:
offset_times = np.array(offset_times, dtype='datetime64[ms]')
offsets = np.interp(utcs.astype(np.uint64),
offset_times.astype(np.uint64),
clock_error)
utcs -= (offsets * 1000).astype('timedelta64[ms]')
t = utcs[0].astype(datetime.datetime)
if "constant_yaw_attitude_error" in self.head.dtype.fields:
rpy = np.deg2rad([
self.head["constant_roll_attitude_error"] / 1e3,
self.head["constant_pitch_attitude_error"] / 1e3,
self.head["constant_yaw_attitude_error"] / 1e3
])
else:
rpy = [0, 0, 0]
LOG.info("Using rpy: %s", str(rpy))
from pyorbital.geoloc_instrument_definitions import avhrr_gac
from pyorbital.geoloc import compute_pixels, get_lonlatalt
sgeom = avhrr_gac(utcs.astype(datetime.datetime), scan_points, 55.385)
s_times = sgeom.times(t)
pixels_pos = compute_pixels((tle1, tle2), sgeom, s_times, rpy)
pos_time = get_lonlatalt(pixels_pos, s_times)
toc = datetime.datetime.now()
LOG.warning("Computation of geolocation: %s", str(toc - tic))
lons, lats = pos_time[:2]
return lons.reshape(-1, width), lats.reshape(-1, width)
def _adjust_clock_drift(self):
"""Adjust the geolocation to compensate for the clock error."""
tic = datetime.datetime.now()
self.get_times()
try:
error_utcs, clock_error = get_offsets(self.spacecraft_name)
except KeyError:
LOG.info("No clock drift info available for %s",
self.spacecraft_name)
return
error_utcs = np.array(error_utcs, dtype='datetime64[ms]')
# interpolate to get the clock offsets at the scan line utcs
# the clock_error is given in seconds, so offsets are in seconds, too.
offsets = np.interp(self.utcs.astype(np.uint64),
error_utcs.astype(np.uint64),
clock_error)
LOG.info("Adjusting for clock drift of %s to %s seconds.",
str(min(offsets)),
str(max(offsets)))
# For the interpolation of geolocations, we need to prepend/append
# lines. The conversion from offset to line numbers is given by the
# scan rate = 1/scan frequency.
scan_rate = datetime.timedelta(milliseconds=1/self.scan_freq)
offset_lines = offsets / scan_rate.total_seconds()
# To avoid trouble with missing lines, we will construct an
# array that covers the whole interpolation range.
scan_lines = self.scans["scan_line_number"]
shifted_lines = scan_lines - offset_lines
shifted_lines_floor = np.floor(shifted_lines).astype(int)
# compute the line range, note that the max requires a "+1"
# to cover the interpolation range because of the floor.
min_line = min(scan_lines.min(), shifted_lines_floor.min())
max_line = max(scan_lines.max(), shifted_lines_floor.max()+1)
num_lines = max_line - min_line + 1
missed_lines = np.setdiff1d(np.arange(min_line, max_line+1), scan_lines)
missed_utcs = ((missed_lines - scan_lines[0])*np.timedelta64(scan_rate, "ms")
+ self.utcs[0])
# calculate the missing geo locations
missed_lons, missed_lats = self._compute_missing_lonlat(missed_utcs)
# create arrays of lons and lats for interpolation. The locations
# correspond to not yet corrected utcs, i.e. the time difference from
# one line to the other should be equal to the scan rate.
pixels_per_line = self.lats.shape[1]
complete_lons = np.full((num_lines, pixels_per_line), np.nan,
dtype=np.float)
complete_lats = np.full((num_lines, pixels_per_line), np.nan,
dtype=np.float)
complete_lons[scan_lines - min_line] = self.lons
complete_lats[scan_lines - min_line] = self.lats
complete_lons[missed_lines - min_line] = missed_lons
complete_lats[missed_lines - min_line] = missed_lats
# perform the slerp interpolation to the corrected utc times
slerp_t = shifted_lines - shifted_lines_floor # in [0, 1)
slerp_res = slerp(complete_lons[shifted_lines_floor - min_line, :],
complete_lats[shifted_lines_floor - min_line, :],
complete_lons[shifted_lines_floor - min_line + 1, :],
complete_lats[shifted_lines_floor - min_line + 1, :],
slerp_t[:, np.newaxis, np.newaxis])
# set corrected values
self.lons = slerp_res[:, :, 0]
self.lats = slerp_res[:, :, 1]
self.utcs -= (offsets * 1000).astype('timedelta64[ms]')
toc = datetime.datetime.now()
LOG.debug("clock drift adjustment took %s", str(toc - tic))
def adjust_clock_drift(self):
"""Adjust the geolocation to compensate for the clock error.
TODO: bad things might happen when scanlines are skipped.
"""
tic = datetime.datetime.now()
self.get_times()
from pygac.clock_offsets_converter import get_offsets
try:
offset_times, clock_error = get_offsets(self.spacecraft_name)
except KeyError:
LOG.info("No clock drift info available for %s",
self.spacecraft_name)
else:
offset_times = np.array(offset_times, dtype='datetime64[ms]')
offsets = np.interp(self.utcs.astype(np.uint64),
offset_times.astype(np.uint64), clock_error)
LOG.info("Adjusting for clock drift of %s to %s",
str(min(offsets)), str(max(offsets)))
self.times = (self.utcs + offsets.astype('timedelta64[s]')).astype(
datetime.datetime)
offsets *= -2
int_offsets = np.floor(offsets).astype(np.int)
# filling out missing geolocations with computation from pyorbital.
line_indices = (self.scans["scan_line_number"] + int_offsets)
missed = sorted((set(line_indices) | set(line_indices + 1)) -
set(self.scans["scan_line_number"]))
min_idx = min(line_indices)
max_idx = max(max(line_indices),
max(self.scans["scan_line_number"] - min_idx)) + 1
idx_len = max_idx - min_idx + 2
complete_lons = np.zeros((idx_len, 409), dtype=np.float) * np.nan
complete_lats = np.zeros((idx_len, 409), dtype=np.float) * np.nan
complete_lons[self.scans["scan_line_number"] - min_idx] = self.lons
complete_lats[self.scans["scan_line_number"] - min_idx] = self.lats
missed_utcs = ((np.array(missed) - 1) * np.timedelta64(500, "ms") +
self.utcs[0])
mlons, mlats = self.compute_lonlat(missed_utcs, True)
complete_lons[missed - min_idx] = mlons
complete_lats[missed - min_idx] = mlats
from pygac.slerp import slerp
off = offsets - np.floor(offsets)
res = slerp(complete_lons[line_indices - min_idx, :],
complete_lats[line_indices - min_idx, :],
complete_lons[line_indices - min_idx + 1, :],
complete_lats[line_indices - min_idx + 1, :],
off[:, np.newaxis, np.newaxis])
self.lons = res[:, :, 0]
self.lats = res[:, :, 1]
self.utcs += offsets.astype('timedelta64[s]')
toc = datetime.datetime.now()
LOG.debug("clock drift adjustment took %s", str(toc - tic))
def compute_lonlat(self, width, utcs=None, clock_drift_adjust=True):
"""Compute lat/lon coordinates.
Args:
width: Number of coordinates per scanlines
utcs: Scanline timestamps
clock_drift_adjust: If True, adjust clock drift.
"""
if utcs is None:
utcs = self.get_times()
# adjusting clock for drift
tic = datetime.datetime.now()
if clock_drift_adjust:
from pygac.clock_offsets_converter import get_offsets
try:
offset_times, clock_error = get_offsets(self.spacecraft_name)
except KeyError:
LOG.info("No clock drift info available for %s",
self.spacecraft_name)
else:
offset_times = np.array(offset_times, dtype='datetime64[ms]')
offsets = np.interp(utcs.astype(np.uint64),
offset_times.astype(np.uint64),
clock_error)
utcs = utcs - (offsets * 1000).astype('timedelta64[ms]')
t = utcs[0].astype(datetime.datetime)
if "constant_yaw_attitude_error" in self.head.dtype.fields:
rpy = np.deg2rad([
self.head["constant_roll_attitude_error"] / 1e3,
self.head["constant_pitch_attitude_error"] / 1e3,
self.head["constant_yaw_attitude_error"] / 1e3
])
else:
try:
# This needs to be checked thoroughly first
# rpy_spacecraft = rpy_coeffs[self.spacecraft_name]
# rpy = [rpy_spacecraft['roll'],
# rpy_spacecraft['pitch'],
# rpy_spacecraft['yaw']]
# LOG.debug("Using static attitude correction")
raise KeyError
except KeyError:
LOG.debug("Not applying attitude correction")
rpy = [0, 0, 0]
LOG.info("Using rpy: %s", str(rpy))
from pyorbital.geoloc_instrument_definitions import avhrr_gac
from pyorbital.geoloc import compute_pixels, get_lonlatalt
# TODO: Are we sure all satellites have this scan width in degrees ?
sgeom = avhrr_gac(utcs.astype(datetime.datetime), self.scan_points,
55.385)
s_times = sgeom.times(t)
tle1, tle2 = self.get_tle_lines()
pixels_pos = compute_pixels((tle1, tle2), sgeom, s_times, rpy)
pos_time = get_lonlatalt(pixels_pos, s_times)
toc = datetime.datetime.now()
LOG.warning("Computation of geolocation: %s", str(toc - tic))
lons, lats = pos_time[:2]
return lons.reshape(-1, width), lats.reshape(-1, width)
