Coherence estimation routine consists of:
- 2 x input SLC coregistration(split + apply orbit file + backgeocoding)
- Coherence estimation
- Deburst
- Merge (when multiple subswaths selected)
- Range doppler terrain correction
- ~22 GB RAM for full scene (3 subswaths)
- ~2 GB GPU memory for full scene (depending on DEM tiles)
ALUs - Coherence estimation routine
Version 1.6.0
Arguments:
-h [ --help ] Print help
-r [ --in_ref ] arg Reference scene's input SAFE dataset
(zipped or unpacked)
-s [ --in_sec ] arg Secondary scene's input SAFE dataset
(zipped or unpacked)
--b_ref1 arg Reference scene's first burst index -
starting at '1', leave unspecified for
whole subswath
--b_ref2 arg Reference scene's last burst index -
starting at '1', leave unspecified for
whole subswath
--b_sec1 arg Secondary scene's first burst index -
starting at '1', leave unspecified for
whole subswath
--b_sec2 arg Secondary scene's last burst index -
starting at '1', leave unspecified for
whole subswath
--orbit_ref arg Reference scene's POEORB/RESORB file.
Can be unspecified.
--orbit_sec arg Secondary scene's POEORB/RESORB file.
Can be unspecified.
-o [ --output ] arg Output folder or filename
-p [ --polarisation ] arg Polarisation for which coherence
estimation will be performed - VV;VH
--sw arg Reference scene's subswath
-a [ --aoi ] arg Area Of Interest WKT polygon. Or
shapefile (.shp) consisting similar
geometry.Overrules first and last burst
indexes and subswath selections.
--dem arg DEM file(s). SRTM3 and Copernicus DEM
30m COG are currently supported.
--no_mask_cor Do not mask out areas without elevation
in coregistration
--orbit_dir arg Directory of orbit files (restituted
and/or precise). Can be used to find
correct one during processing. Can be
unspecified - hence no orbital
information is updated. Also supports
ESA SNAP compatible folder for example:
/home/<user>/.snap/auxData/Orbits/Senti
nel-1/POEORB/
--srp_number_points arg (=501)
--srp_polynomial_degree arg (=5)
--subtract_flat_earth_phase arg (=1) Compute flat earth phase subtraction
during coherence operation. By default
on.
--rg_win arg (=15) range window size in pixels.
--az_win arg (=0) azimuth window size in pixels, if zero
derived from range window.
--orbit_degree arg (=3)
-w [ --wif ] Write intermediate results (will be
saved in the same folder as final
outcome). NOTE - this may decrease
performance. By default off.
--ll arg (=verbose) Log level, one of the following -
verbose|debug|info|warning|error
--gpu_mem arg (=100) Percentage of how much GPU memory can
be used for processing
https://github.com/cgi-estonia-space/ALUs
-h [ --help ] Print help
-i [ --input ] arg Timeline search directory
-s [ --timeline_start ] arg Timeline start - format YYYYMMDD
-e [ --timeline_end ] arg Timeline end - format YYYYMMDD
-m [ --timeline_mission ] arg Timeline mission filter - S1A or S1B
-o [ --output ] arg Output folder or filename
-p [ --polarisation ] arg Polarisation for which coherence
estimation will be performed - VV;VH
--sw arg Reference scene's subswath
-a [ --aoi ] arg Area Of Interest WKT polygon, overrules
first and last burst indexes
--dem arg DEM file(s). Only SRTM3 is currently
supported.
--no_mask_cor Do not mask out areas without elevation
in coregistration
--orbit_dir arg Directory of orbit files (restituted
and/or precise). Can be used to find
correct one during processing. Can be
unspecified - hence no orbital
information is updated. Also supports
ESA SNAP compatible folder for example:
/home/<user>/.snap/auxData/Orbits/Senti
nel-1/POEORB/
--srp_number_points arg (=501)
--srp_polynomial_degree arg (=5)
--subtract_flat_earth_phase arg (=1) Compute flat earth phase subtraction
during coherence operation. By default
on.
--rg_win arg (=15) range window size in pixels.
--az_win arg (=0) azimuth window size in pixels, if zero
derived from range window.
--orbit_degree arg (=3)
-w [ --wif ] Write intermediate results (will be
saved in the same folder as final
outcome). NOTE - this may decrease
performance. By default off.
--ll arg (=verbose) Log level, one of the following -
verbose|debug|info|warning|error
--gpu_mem arg (=100) Percentage of how much GPU memory can
be used for processing
Please see the latest and always updated comprehensive evaluation in the Wiki
Following contents below might be deprecated
Reference laptop computer details:
CPU: Intel i7 10750h
RAM: 32GB
GPU: NVIDIA GeForce GTX 1660 Ti 6GB
SSD (NVMe): SAMSUNG MZALQ512HALU-000L2
Compared against SNAP 8 GPT on Ubuntu 20.04.
Configuration:
-Xmx22381m
-Xms2048m
-XX:+AggressiveOpts
-Xverify:none
-Dnetbeans.mainclass=org.esa.snap.main.Main
-Dsun.java2d.noddraw=true
-Dsun.awt.nopixfmt=true
-Dsun.java2d.dpiaware=false
Tile size 512
Number of threads 12
Inputs:
- S1A_IW_SLC__1SDV_20210703T055050_20210703T055117_038609_048E45_35F7.SAFE
- S1B_IW_SLC__1SDV_20210721T055001_20210721T055028_027888_0353E2_E1B5.SAFE
Processing options:
- Subswath IW2 (all bursts)
- Polarisation VV
For more raw computing comparison, the IW2 subswath GeoTIFF file has been stored on ram disk - this way I/O influences results less. Also outputs are stored on ram disk.
When using SRTM3 DEM
./gpt coherence_estimation_snap_graph.xml -Preference=S1A_IW_SLC__1SDV_20210703T055050_20210703T055117_038609_048E45_35F7.SAFE/manifest.safe
-Psecondary=S1B_IW_SLC__1SDV_20210721T055001_20210721T055028_027888_0353E2_E1B5.SAFE/manifest.safe -Psw=IW2 -Ppol=VV
-Poutput=/mnt/ramdisk/snap_iw2.tif
~85.666 seconds
./alus-coh -r S1A_IW_SLC__1SDV_20210703T055050_20210703T055117_038609_048E45_35F7.SAFE
-s S1B_IW_SLC__1SDV_20210721T055001_20210721T055028_027888_0353E2_E1B5.SAFE --orbit_dir flood_in_belgium_germany/aux
--sw IW2 -p VV -o /mnt/ramdisk --dem flood_in_belgium_germany/aux/srtm_37_02.tif
--dem flood_in_belgium_germany/aux/srtm_37_03.tif --dem flood_in_belgium_germany/aux/srtm_38_02.tif
--dem flood_in_belgium_germany/aux/srtm_38_03.tif --ll info --no_mask_cor
~13.4 seconds
gdal_calc.py -A S1A_IW_SLC__1SDV_20210703T055050_20210703T055117_038609_048E45_35F7_Orb_Stack_coh_deb_TC_no_data.tif
-B S1A_IW_SLC__1SDV_20210703T055050_20210703T055117_038609_048E45_35F7_Orb_Stack_coh_deb_tc.tif --calc="A-B"
--outfile=snap_man_min_alus_diff.tif --NoDataValue=0
Resulting diff file statistics:
Band 1 Block=14224x1 Type=Float32, ColorInterp=Gray
Min=-0.873 Max=0.311
Minimum=-0.873, Maximum=0.311, Mean=-0.000, StdDev=0.003
NoData Value=3.40282346600000016e+38
Metadata:
STATISTICS_MAXIMUM=0.31110879778862
STATISTICS_MEAN=-7.2791041110424e-05
STATISTICS_MINIMUM=-0.87261736392975
STATISTICS_STDDEV=0.0033343616817697
STATISTICS_VALID_PERCENT=43.46
Legend
Orbit state vector related, see cause
For Copernicus DEM such comparison is not done because of the pending issues found in the SNAP - https://forum.step.esa.int/t/copernicus-dem-complications-when-coregistering-s1/38659/2