def split_at_large_non_ocean_segments(self, l1):
"""
Identify larger segments that are not ocean (land, land ice) and split the segments if necessary.
The return value will always be a list of Level-1 object instances, even if no non-ocean data
segment is present in the input data file
:param l1: Input Level-1 object
:return: a list of Level-1 objects.
"""
# Identify connected non-ocean segments within the orbit
ocean = l1.surface_type.get_by_name("ocean")
not_ocean_flag = np.logical_not(ocean.flag)
segments_len, segments_start, not_ocean = rle(not_ocean_flag)
landseg_index = np.where(not_ocean)[0]
# no non-ocean segments, return full segment
if len(landseg_index) == 0:
return [l1]
# Test if non-ocean segments above the size threshold that will require a split of the segment.
# The motivation behind this step to keep l1p data files as small as possible, while tolerating
# smaller non-ocean sections
treshold = self.cfg.polar_ocean.allow_nonocean_segment_nrecords
large_landsegs_index = np.where(
segments_len[landseg_index] > treshold)[0]
large_landsegs_index = landseg_index[large_landsegs_index]
# no segment split necessary, return full segment
if len(large_landsegs_index) == 0:
return [l1]
# Split of orbit segment required, generate individual Level-1 segments from the ocean segments
l1_segments = []
start_index = 0
for index in large_landsegs_index:
stop_index = segments_start[index]
subset_list = np.arange(start_index, stop_index)
l1_segments.append(l1.extract_subset(subset_list))
start_index = segments_start[index + 1]
# Extract the last subset
last_subset_list = np.arange(start_index, len(ocean.flag))
l1_segments.append(l1.extract_subset(last_subset_list))
# Return a list of segments
return l1_segments
def split_at_large_non_ocean_segments(self, l1b):
"""
Identify larger segments that are not ocean (land, land ice)
and split the segments if necessary
"""
# Find connected nonocean segments
self.log.info("- test for inner larger landmasses")
ocean = l1b.surface_type.get_by_name("ocean")
not_ocean_flag = np.logical_not(ocean.flag)
segments_len, segments_start, not_ocean = rle(not_ocean_flag)
landseg_index = np.where(not_ocean)[0]
self.log.info("- number of landmasses: %g" % len(landseg_index))
# no land segements, return segment
if len(landseg_index) == 0:
return [l1b]
# Test if nonocean segments above threshold
treshold = self._mdef.max_inner_nonocean_segment_nrecords
large_landsegs_index = np.where(
segments_len[landseg_index] > treshold)[0]
large_landsegs_index = landseg_index[large_landsegs_index]
self.log.info("- number of large landmasses: %g" % len(
large_landsegs_index))
# no large land segments, return segment
if len(large_landsegs_index) == 0:
return [l1b]
# Large land segments exist, split the l1b data object
l1b_segments = []
start_index = 0
for index in large_landsegs_index:
stop_index = segments_start[index]
subset_list = np.arange(start_index, stop_index)
l1b_segments.append(l1b.extract_subset(subset_list))
start_index = segments_start[index+1]
# extract the last subset
last_subset_list = np.arange(start_index, len(ocean.flag))
l1b_segments.append(l1b.extract_subset(last_subset_list))
# Return a list of segments
return l1b_segments
def filter_small_ocean_segments(self, l1):
"""
This method sets the surface type flag of very small ocean segments to land. This action should prevent
large portions of land staying in the l1 segment is a small fjord etc is crossed. It should also filter
out smaller ocean segments that do not have a realistic chance of freeboard retrieval.
:param l1: A pysiral.l1bdata.Level1bData instance
:return: filtered l1 object
"""
# Minimum size for valid ocean segments
ocean_mininum_size_nrecords = self.cfg.polar_ocean.ocean_mininum_size_nrecords
# Get the clusters of ocean parts in the l1 object
ocean_flag = l1.surface_type.get_by_name("ocean").flag
land_flag = l1.surface_type.get_by_name("land").flag
segments_len, segments_start, not_ocean = rle(ocean_flag)
# Find smaller than threshold ocean segments
small_cluster_indices = np.where(
segments_len < ocean_mininum_size_nrecords)[0]
# Do not mess with the l1 object if not necessary
if len(small_cluster_indices == 0):
return l1
# Set land flag -> True for small ocean segments
for small_cluster_index in small_cluster_indices:
i0 = segments_start[small_cluster_index]
i1 = i0 + segments_len[small_cluster_index]
land_flag[i0:i1] = True
# Update the l1 surface type flag by re-setting the land flag
l1.surface_type.add_flag(land_flag, "land")
# All done
return l1
