P-SBAS Sentinel-1 processing on-demand by CNR-IREA¶

1.1 Select the processing¶

• Sign-in on the Portal https://geohazards-tep.eo.esa.int/
• Access the “CNR IREA SBAS Ground Motion Services” Thematic App.
• Open the tab “Processing services” from the right of the map, and then select the processing service “CNR-IREA P-SBAS Sentinel-1 processing on-demand”.

1.2 Select the files to process¶

Input SAR data selection must be carried out with particular care, since a wrong data selection can result to an unfeasible processing.

• The algorithm accepts as inputs IW Sentinel-1 SLC (level 1) data. RAW data cannot be processed.
• It is very important that the user selects images related to the same track only which must be aquired with the same mode (the IW one).
• The system automatically discards duplicated (reprocessed) images and correctly mosaicks SAR data belonging to different “portions” (slices) of the same strip. In case of reprocessed (duplicated) images the newest one is selected.
• Note that to obtain reliable displacement measurements and to avoid processing failures, it is strongly suggested to select a number of epochs greater then 20 in the case of time series generation mode.

For this tutorial, a pre-defined data set has been prepared to speed up the data selection step .

• Browse the Data Packages looking for Napoli S1 T22 2017 package and click on the load button to upload it.

• Surf the map to the Napoli (Italy) Area of Interest: the browser page should appear as depicted in the next figure.

• Set the Job Title with a meaningful name (e.g. CNR-IREA P-SBAS S1 Napoli T22 2017 - v1.0.9) and push the sel. all button in the Feature Basket.

• Drag all the selected data and drop them within the Sentinel-1 input SLCs field on the right panel.

1.3 Fill the parameter values¶

• Fill the parameters according to the following figure:

In particular:

• As Latitude of the Reference Point, type:

40.848

• As Longitude of the Reference Point, type:

14.262

• Leave the Bounding Box untouched (Area of Interest empty).

• As Polarization type:

vv

• As Processing Mode, select:

MTA

• As DEM, select:

srtm_1

• As APS Filter Window Length, insert:

200

1.4 Run the job¶

• Click on the button “Run Job” at the bottom of the P-SBAS DInSAR processor tab, and monitor the progress of the running Job:
• After about 48 hours of processing time, the job status should be “Success”.

1.5 Results: download and visualization¶

Download

The P-SBAS DInSAR results are available in the Geobrowser after the processing. Scroll down the right panel and push the “Show results” button. Tutorial results are accessible here.

To download the P-SBAS DInSAR processing results once the Job is completed just click on the Download button in the pop-up window of the identified product:

Visualization

Time series can be directly visualized via the Geobrowser. After setting a satisfactory zoom, put a Placemark on the pixel for which the time series shold be displayed. Then click the “plot” icon in the TS collection.

A pop-up window should appear showing the Time series of the selected pixel.

Conventions and assumptions

Results are provided in the satellite Line Of Sight (LOS). Positive values indicate that the target moves toward the satellite. Processing results are provided according to the EPOS-IP project specifications along with the corresponding metadata.

Published Results

The main outputs of the MTA mode are the:

• Displacement Time series in LOS;
• Mean LOS velocity;
• Temporal coherence;
• Pixel location (coordinates);
• LOS unit vectors.

Information is organized in a CSV ASCII table according to the following figure.

Provided information consists, per each pixel considered reliable, in:

• Unique pixel identifier (ID);
• WGS84 Latitude in degree (Lat);
• WGS84 Longitude in degree (Lon);
• Topography above the ellipsoid (Topo);
• Mean Velocity in cm/year, as linear regression of the displacement Time series (Vel);
• Temporal coherence (Coer);
• Components of LOS unit vector along the North, East and Vertical directions (cosN, cosE, cosU);
• LOS displacement time-series in cm (TS): the length of this field depends on the number of acquisitions used in the time series generation.

File name convention is as follows:

SBAS_TS_<FirstAcqDate>_<LastAcqDate>_<UniqueCode>.csv

where:

• <FirstAcqDate>: is the first acquisition of the time series;
• <LastAcqDate> : is the last acquisition of the time series.
• <UniqueCode> : is a unique code identifier.

A typical name sample is: SBAS_TS_20170106_20171120_ME7G.csv

Additional provided outputs are:

• A .kmz file containing the Quick-look of the retrieved mean LOS velocity importable in Google Earth;
• A .png file (together with its .pngw file) containing the raster bitmap image of the mean LOS velocity;
• A .properties file containing the Metadata associated to the main results and displayed in the Geobrowser pop-up window;
• A .png file representing the mean LOS velocity legend, i.e. the color code associated to the LOS Mean Velocity values;
• A .zip archive that contains all the mentioned result files.

1.6 Metadata¶

Metadata are provided according to the EPOS specifications.

2.1 Select the processing¶

• Follow the steps described in Section 1.1.

2.2 Select the files to process¶

Input SAR data selection must be carried out with particular care, since a wrong data selection can result to an unfeasible processing.

• The algorithm accepts as inputs IW Sentinel-1 SLC (level 1) data. RAW data cannot be processed.
• It is very important that the user selects images related to the same track only which must be aquired with the same mode (the IW one).
• The system automatically discards duplicated (reprocessed) images and correctly mosaicks SAR data belonging to different “portions” (slices) of the same strip. In case of reprocessed (duplicated) images the newest one is selected.
• Note that to obtain reliable displacement measurements and to avoid processing failures, it is strongly suggested to select a number of epochs greater then 20 in the case of time series generation mode.

For this tutorial, a pre-defined data set has been prepared to speed up the data selection step.

• Browse the Data Packages looking for Amatrice IFG S1 T22 package and click on the load button to upload it.

• Surf the map to the Central Italy Area of Interest: the browser page should appear as depicted in the next figure.

• Set the Job Title with a meaningful name (e.g. CNR-IREA P-SBAS S1 on-demand Amatrice T22) and push the sel. all button in the Feature Basket.
• Drag all the selected data and drop them within the Sentinel-1 input SLCs field on the right panel.

2.3 Fill the parameter values¶

• Fill the parameters according to the following figure:

In particular:

• As Latitude of the Reference Point, type:

43.277

• As Longitude of the Reference Point, type:

13.733

• Leave the Bounding Box untouched (Area of Interest empty).

• As Polarization type:

vv

• As Processing Mode, select:

IFG

• As DEM, select:

srtm_1

• Leave the APS Filter Window Length unchanged.

2.4 Run the job¶

• Click on the button “Run Job” at the bottom of the P-SBAS DInSAR processor tab, and monitor the progress of the running Job:
• After about 4 hours of processing time, the job status should be as “Success”.

2.5 Results: download and visualization¶

The P-SBAS DInSAR results are available in the Geobrowser after the processing. Scroll down the right panel and push the “Show results” button. Tutorial results are accessible here.

To download the P-SBAS DInSAR processing results once the Job is completed just click on the Download button in the pop-ip window of the identified product:

Conventions and assumptions

Results are provided in the satellite Line Of Sight (LOS). Positive values indicate that the target moves toward the satellite. Processing results are provided according to the EPOS-IP project specifications along with the corresponding metadata.

Published Results

The IFG mode outputs are provided in geoTiff standard and consist in:

• geocoded interferograms (filtered and not filtered according to the Goldstein method);
• geocoded spatial coherence maps.

The spacing of the output depends on the DEM used for the processing. Results are provided in WGS84 geographic projection.

File name convention is as follows:

<DataType>_<MasterDate>_<SlaveDate>_<UniqueCode>.<FileExtension>

where:

• <DataType> can be: InW (Wrapped Interferogram), InU (Unwrapped Interferogram) (this feature will be available in a later release of the service), Coh (Spatial Coherence);
• <MasterDate> date of the Master acquisition in the format <yyyymmdd><SensorCode>, where <SensorCode> is a 3-char code that identifies the sensor. For the Sentinel case the possible codes are: S1A and S1B.
• <SlaveDate> date of the Slave acquisition in the same <MasterDate> format;
• <UniqueCode> a unique code identifier;
• <FileExtension> possible values are:
  • tif: the actual data in geoTiff;
  • properties: the metadata displayed in the Geobrowser;
  • metadata: the full metadata list according to the EPOS specifications;
  • png: a quick-look raster image;
  • pngw: the geocoding information for the png image;
  • kmz: the google format overlay containing the quick-look image;
  • legend.png: the color bar for the png image.

Typical name samples are:

InW_20160821S1A_20160827S1B_7M1E.tif
Coh_20160821S1A_20160827S1B_7M1E.tif

2.6 Metadata¶

Metadata are provided according to the EPOS specifications. See Table in Section 1.6 for more details.