Track Filtering

ICESat-2 and GEDI emit multiple beams simultaneously. By default table(g) reads all beams, returning a PartitionedH5Table with one partition per beam. Use the tracks keyword to restrict which beams are loaded.

ICESat-2 beams

ICESat-2 has 6 beam pairs: gt1l, gt1r, gt2l, gt2r, gt3l, gt3r. Strong and weak beams alternate based on spacecraft orientation.

using SpaceLiDAR

g = granule("ATL08_20201121151145_08920913_006_01.h5")

# Only left beams
t = table(g; tracks=["gt1l", "gt2l", "gt3l"])

# Single beam
t = table(g; tracks=["gt1l"])

GEDI beams

GEDI has 8 beams: BEAM0000, BEAM0001, BEAM0010, BEAM0011, BEAM0101, BEAM0110, BEAM1000, BEAM1011.

g = granule("GEDI02_A_2019242104318_O04046_01_T02343_02_003_02_V002.h5")

# Full-power beams only
t = table(g; tracks=["BEAM0101", "BEAM0110", "BEAM1000", "BEAM1011"])

Default tracks

To see what tracks are read by default for a granule:

SpaceLiDAR.default_tracks(g)
# ("gt1l", "gt1r", "gt2l", "gt2r", "gt3l", "gt3r")  for ICESat-2
# ("BEAM0000", ..., "BEAM1011")                       for GEDI

ICESat (GLAH) has no beam structure — table(g) always returns a single table.

Iterating over tracks

Each partition in a PartitionedH5Table corresponds to one track:

using DataFrames, Tables

t = table(g)
for part in Tables.partitions(t)
    df = DataFrame(part)
    # process one beam at a time
end