📊 Understanding HDF5

import h5py
import numpy as np

# Create INTERFEROGRAM product
with h5py.File('my_interferogram.h5', 'w') as f:
    
    # Root attributes
    f.attrs['processing_type'] = 'INTERFEROGRAM'
    f.attrs['processing_software'] = 'ISCE2 v2.6.3 + SNAPHU v2.0.5'
    f.attrs['sign_convention'] = 'Positive LOS displacement corresponds to surface motion toward the sensor'
    
    # Create track
    track = f.create_group('ALOS2_073_A')
    track.attrs['platform'] = 'ALOS-2'
    track.attrs['relative_orbit'] = 73
    track.attrs['flight_direction'] = 'A'
    track.attrs['look_direction'] = 'R'
    track.attrs['beam_mode'] = 'WD1'
    track.attrs['beam_swath'] = 'W1'
    track.attrs['wavelength'] = 0.236
    track.attrs['first_date'] = '2024-01-01'
    track.attrs['last_date'] = '2024-02-08'
    track.attrs['time_acquisition'] = '10:23'
    track.attrs['scene_footprint'] = 'POLYGON((-118.5 34.0, -118.0 34.0, -118.0 34.5, -118.5 34.5, -118.5 34.0))'
    
    # LOS vectors (track-specific)
    los_e_data = np.random.uniform(0.35, 0.45, (1000, 1200)).astype('float32')
    los_e = track.create_dataset('line_of_sight_e', data=los_e_data, compression='gzip')
    los_e.attrs['description'] = 'LOS unit vector - East component'
    los_e.attrs['units'] = 'dimensionless'
    
    # Create interferogram group (date pair)
    ifg_group = track.create_group('20240101_20240113')
    ifg_group.attrs['reference_date'] = '20240101'
    ifg_group.attrs['secondary_date'] = '20240113'
    ifg_group.attrs['temporal_baseline_days'] = 12
    ifg_group.attrs['baseline_perp'] = 45.2
    
    # Add unwrapped phase (radians)
    unwrapped_data = np.random.randn(1000, 1200).astype('float32')
    unwrapped = ifg_group.create_dataset('unwrapped_interferogram', 
                                         data=unwrapped_data, compression='gzip')
    unwrapped.attrs['description'] = 'Unwrapped interferometric phase'
    unwrapped.attrs['units'] = 'radians'

print("✅ Interferogram file created!")

import h5py
import numpy as np

# Create DISP. TIME SERIES product
with h5py.File('my_timeseries.h5', 'w') as f:
    
    # Root attributes
    f.attrs['processing_type'] = 'DISP. TIME SERIES'
    f.attrs['processing_software'] = 'MintPy v1.5.1'
    f.attrs['sign_convention'] = 'Positive LOS displacement corresponds to surface motion toward the sensor'
    
    # Create track
    track = f.create_group('ALOS2_073_A')
    track.attrs['platform'] = 'ALOS-2'
    track.attrs['relative_orbit'] = 73
    track.attrs['flight_direction'] = 'A'
    track.attrs['look_direction'] = 'R'
    track.attrs['beam_mode'] = 'WD1'
    track.attrs['beam_swath'] = 'W1'
    track.attrs['wavelength'] = 0.236
    track.attrs['first_date'] = '2024-01-01'
    track.attrs['last_date'] = '2024-04-01'
    track.attrs['time_acquisition'] = '10:23'
    track.attrs['scene_footprint'] = 'POLYGON((-118.5 34.0, -118.0 34.0, -118.0 34.5, -118.5 34.5, -118.5 34.0))'
    
    # REQUIRED: Track-specific reference date for time series
    track.attrs['reference_date'] = '20240101'
    
    # LOS vectors
    los_e_data = np.random.uniform(0.35, 0.45, (1000, 1200)).astype('float32')
    los_e = track.create_dataset('line_of_sight_e', data=los_e_data, compression='gzip')
    los_e.attrs['units'] = 'dimensionless'
    
    # Create displacement time series (note: no date-pair groups!)
    dates = ['20240101', '20240113', '20240125', '20240208']
    
    for i, date in enumerate(dates):
        if i == 0:
            # Reference date: all zeros
            disp_data = np.zeros((1000, 1200), dtype='float32')
        else:
            # Cumulative displacement in meters
            disp_data = np.random.randn(1000, 1200).astype('float32') * 0.01 * i
        
        # Create dataset: dLOS_YYYYMMDD
        dset = track.create_dataset(f'dLOS_{date}', data=disp_data, compression='gzip')
        dset.attrs['description'] = 'Cumulative LOS displacement relative to reference date'
        dset.attrs['units'] = 'meters'  # Note: meters, not radians!
        dset.attrs['acquisition_date'] = date
        dset.attrs['reference_date'] = '20240101'

print("✅ Time series file created!")

import h5py

# Open any InSAR HDF5 file
with h5py.File('my_insar_file.h5', 'r') as f:
    
    # Check processing type
    proc_type = f.attrs['processing_type']
    print(f"Processing type: {proc_type}")
    
    # Get track
    track = f['ALOS2_073_A']
    print(f"Platform: {track.attrs['platform']}")
    
    # Read LOS vectors (same for all product types)
    los_e = track['line_of_sight_e'][:]
    los_n = track['line_of_sight_n'][:]
    los_u = track['line_of_sight_u'][:]
    
    # Read data based on product type
    if proc_type == 'INTERFEROGRAM':
        print("\nReading interferogram...")
        # List interferogram date pairs
        ifgs = [key for key in track.keys() if '_' in key and len(key) == 17]
        print(f"Found {len(ifgs)} interferogram(s): {ifgs}")
        
        # Read specific interferogram
        ifg = track['20240101_20240113']
        unwrapped = ifg['unwrapped_interferogram'][:]
        print(f"Unwrapped phase shape: {unwrapped.shape}")
        print(f"Units: {ifg['unwrapped_interferogram'].attrs['units']}")  # radians
    
    elif proc_type == 'DISP. TIME SERIES':
        print("\nReading time series...")
        # Check for track-specific reference date (REQUIRED)
        ref_date = track.attrs['reference_date']
        print(f"Track reference date: {ref_date}")
        
        # List all displacement dates
        dates = [key.replace('dLOS_', '') for key in track.keys() 
                 if key.startswith('dLOS_')]
        dates.sort()
        print(f"Found {len(dates)} date(s): {dates}")
        
        # Read specific date
        disp = track['dLOS_20240113'][:]
        print(f"Displacement shape: {disp.shape}")
        print(f"Units: {track['dLOS_20240113'].attrs['units']}")  # meters
    
    elif proc_type == 'LOS_VELOCITY':
        print("\nReading velocity...")
        velocity = track['velocity'][:]
        print(f"Velocity shape: {velocity.shape}")
        print(f"Units: {track['velocity'].attrs['units']}")  # m/year
        print(f"Time span: {track['velocity'].attrs['time_span_start']} to "
              f"{track['velocity'].attrs['time_span_end']}")

print("✅ File read successfully!")