sentinel1_decode

For additional information on Level-0 product decoding, see the SAR Space Packet Protocol Data Unit Specification and the Sentinel-1 Level-0 Data Decoding Package.

Table of Contents

• Introduction
• Commands and Examples
  • Image Writing
  • Plotting
  • Packet Information and Performance Testing
• Results with Point Targets
• Compiling
  • Build Script
  • Dependencies

Introduction

sentinel1_decode is a C++ program/library for quickly decoding Level-0 Raw data from the Sentinel-1 satellite. I am also working on implementing most of the Level-1 Algorithm. I am creating this as an education experience for myself, and because there isn't a good fast, simple, and robust program for decoding this data in a way that allows you to get the intermediate products and signals. Currently, azimuth compression of a full stripmap image takes ~2 minutes, including the time it takes to decode the raw data.

Commands

Writing Images

$ bin/s1_write --help
burst [swath] [burst_num] [in_path] [out_path]
swath [swath] [in_path] [out_path]
burst_replica_chirps [swath] [burst_num] [in_path] [out_path]
swath_replica_chirps [swath] [in_path] [out_path]
range_compressed_burst [swath] [burst_num] [in_path] [out_path]
range_compressed_swath [swath] [in_path] [out_path]
azimuth_compressed_burst [swath] [burst_num] [in_path] [out_path]
azimuth_compressed_swath [swath] [in_path] [out_path]
Scaling Options: [--norm_log|--norm|--mag|--real|--imag]

Examples

The sample image data/points/point.dat is the VV data from S1A_IW_RAW__0SDV_20240813T095440_20240813T095513_055193_06BA22_1119-RAW. The colors were added via Singleband psuedocolor with Cumulative cut count in QGIS.

$ bin/s1_write azimuth_compressed_swath S1 data/sm_sample/sample.dat AZ_S1.tif --norm

$ bin/s1_write swath IW2 data/points/point.dat IW2.tif --norm

$ bin/s1_write range_compressed_swath IW2 data/points/point.dat RC_IW2.tif --norm

$ bin/s1_write azimuth_compressed_swath IW2 data/points/point.dat AZ_IW2.tif --norm

Packet Information and Performance Testing

$ bin/main --help
print_packet_info [packet_index] [path]
print_complex_samples [packet_index] [path]
print_swath_names [path]
print_index_records [path]
print_annotation_record [record_index] [path]
time [num_packets] [path]
thread_test [path]
omp_test [path]

Examples

The sample image data/sample/sample.dat is the VV data from S1A_IW_RAW__0SDV_20240806T135224_20240806T135256_055093_06B68A_AE41

$ bin/main print_packet_info 0 data/sample/sample.dat
Primary Header:
packet_version_number: 0
packet_type: 0
secondary_header_flag: 1
process_id: 65
process_category: 12
sequence_flags: 3
packet_sequence_count: 11157
packet_data_length: 18621

Secondary Header:
coarse_time: 1406987562
fine_time: 7757
sync_marker: 892270675
data_take_id: 225252800
ecc_number: 8
test_mode: 0
rx_channel_id: 0
instrument_configuration_id: 7
sc_data_word_index: 27
sc_data_word: 48835
space_packet_count: 240533
pri_count: 243384
error_flag: 0
baq_mode: 12
baq_block_length: 31
range_decimation: 8
rx_gain: 8
tx_ramp_rate_sign: 1
tx_ramp_rate_mag: 1605
pulse_start_frequency_sign: 0
pulse_start_frequency_mag: 12335
pulse_length: 1967
rank: 9
pri: 21859
swst: 3681
swl: 13979
ssb_flag: 0
polarisation: 7
temperature_compensation: 3
elevation_beam_address: 6
azimuth_beam_address: 385
calibration_mode: 0
tx_pulse_number: 6
signal_type: 0
swap: 1
swath_number: 10
num_quadratures: 11938

Operating Mode Info:
Data Format: D
BAQ Mode: fdbaq_mode_0
BAQ Block Length: 256
Test Mode: measurement_mode
Sensor Mode: interferomatric_wide_swath
Signal Type: echo
Error Status: nominal

Pulse Info:
Swath: IW1
RX Polarization: V
TX Polarization: V
Pulse Length: 52.4048
TX Ramp Rate (TXPRR): 1.07823
Start Frequency (TXPSF): -28.2515
PRI: 582.367
SWL: 372.428
SWST: 98.0692
RX Gain: -4
Range Decimation: 8
TX Pulse Number: 6

$ bin/main print_complex_samples 0 data/sample/sample.dat
# 50,000 lines later...
...
(-11.201,1.59988)
(1.59988,8.00034)
(-4.80058,-11.201)
(-4.80058,20.8031)
(4.80058,4.80058)
(17.6024,17.6024)
(4.80058,31.7194)
(-14.4017,8.00034)
(-11.201,20.8031)
(-4.80058,1.59988)
(1.59988,-4.80058)
(-8.00034,-4.80058)
(-4.80058,-14.4017)
(1.59988,11.201)
(1.59988,-4.80058)

Compiling

Using cmake:

cd build
cmake ..
cmake --build .

Dependencies

My goal is to not involve too many external dependancies; however, some are necessary. OpenMP and FFTW3 are required. The image writing is done via libtiff. The plotting functionality also uses OpenCV.