<commit_before>SNAP-InSAR – SNAP Sentinel-1 IW SLC Interferogram and Displacements
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

.. image:: assets/tuto_snap_s1_insar_icon.png
        
**SNAP-InSAR – SNAP Sentinel-1 IW SLC Interferogram and Displacements**

This service provides the interferometric processor for the Sentinel-1 TOPSAR IW SLC data performed through SNAP. SNAP is a common architecture for all Sentinel Toolboxes, which is ideal for Earth Observation processing and analysis.

**EO sources supported**:

    - Sentinel-1 TOPSAR IW SLC

**Output specifications**

The service provides 3 output products.

+-------------------------------+---------------------------------------------------------------------------------------------------------------+
| Output-1 - Coherence product                                                                                                                  |
+===============================+===============================================================================================================+
| Correspondent file            | Coherence product                                                                                             |
+-------------------------------+---------------------------------------------------------------------------------------------------------------+
| Information types             | Interferometric Coherence computed on input SLC couple                                                        |
+-------------------------------+---------------------------------------------------------------------------------------------------------------+
| Raster format                 | GeoTIFF                                                                                                       |
+-------------------------------+---------------------------------------------------------------------------------------------------------------+
| resolution                    | Native or User selection                                                                                      |
+-------------------------------+---------------------------------------------------------------------------------------------------------------+
| Projection types              | EPSG:4326 - WGS84                                                                                             |
+-------------------------------+---------------------------------------------------------------------------------------------------------------+
| Bit depth                     | Float 32                                                                                                      |
+-------------------------------+---------------------------------------------------------------------------------------------------------------+
| Processing Level              | L2                                                                                                            |
+-------------------------------+---------------------------------------------------------------------------------------------------------------+
| Physical product available    | YES                                                                                                           |
+-------------------------------+---------------------------------------------------------------------------------------------------------------+
| Browse product available      | YES (Both PNG and GeoTIFF)                                                                                    |
+-------------------------------+---------------------------------------------------------------------------------------------------------------+
| Output Filename example       | coh_VV_18Oct2020_30Oct2020 											|   
+-------------------------------+---------------------------------------------------------------------------------------------------------------+

|

+-------------------------------+---------------------------------------------------------------------------------------------------------------+
| Output-2 – Phase product                                                                                                                      |
+===============================+===============================================================================================================+
| Correspondent file            | Phase product                                                                                                 |
+-------------------------------+---------------------------------------------------------------------------------------------------------------+
| Information types             | Interferometric Phase computed on input SLC couple                                                            |
+-------------------------------+---------------------------------------------------------------------------------------------------------------+
| Raster format                 | GeoTIFF                                                                                                       |
+-------------------------------+---------------------------------------------------------------------------------------------------------------+
| resolution                    | Native or User selection                                                                                      |
+-------------------------------+---------------------------------------------------------------------------------------------------------------+
| Projection types              | EPSG:4326 - WGS84                                                                                             |
+-------------------------------+---------------------------------------------------------------------------------------------------------------+
| Bit depth                     | Float 32                                                                                                      |
+-------------------------------+---------------------------------------------------------------------------------------------------------------+
| Processing Level              | L2                                                                                                            |
+-------------------------------+---------------------------------------------------------------------------------------------------------------+
| Physical product available    | YES                                                                                                           |
+-------------------------------+---------------------------------------------------------------------------------------------------------------+
| Browse product available      | YES (Both PNG and GeoTIFF)                                                                                    |
+-------------------------------+---------------------------------------------------------------------------------------------------------------+
| Output Filename example       | phase_VV_18Oct2020_30Oct2020 											|
+-------------------------------+---------------------------------------------------------------------------------------------------------------+

|

+-------------------------------+---------------------------------------------------------------------------------------------------------------+
| Output-3 – Displacement product                                                                                                               |
+===============================+===============================================================================================================+
| Correspondent file            | Displacement product                                                                                          |
+-------------------------------+---------------------------------------------------------------------------------------------------------------+
| Information types             | Line of sight displacement                                                                                    |
+-------------------------------+---------------------------------------------------------------------------------------------------------------+
| Raster format                 | GeoTIFF                                                                                                       |
+-------------------------------+---------------------------------------------------------------------------------------------------------------+
| resolution                    | Native or User selection                                                                                      |
+-------------------------------+---------------------------------------------------------------------------------------------------------------+
| Projection types              | EPSG:4326 - WGS84                                                                                             |
+-------------------------------+---------------------------------------------------------------------------------------------------------------+
| Bit depth                     | Float 32                                                                                                      |
+-------------------------------+---------------------------------------------------------------------------------------------------------------+
| Processing Level              | L2                                                                                                            |
+-------------------------------+---------------------------------------------------------------------------------------------------------------+
| Physical product available    | YES                                                                                                           |
+-------------------------------+---------------------------------------------------------------------------------------------------------------+
| Browse product available      | YES (Both PNG and GeoTIFF)                                                                                    |
+-------------------------------+---------------------------------------------------------------------------------------------------------------+
| Output Filename example       | displacement_VV_18Oct2020_30Oct2020 										|
+-------------------------------+---------------------------------------------------------------------------------------------------------------+

.. NOTE::

    - the "Browse GeoTIFF" product is always a GeoTIFF file with the same resolution of the physical product, with Uint8 bit depth and projection EPSG:3857.
    - The “Browse PNG” product is always a PNG file with the same resolution of the physical product, with Uint8 bit depth.


-----

This tutorial processes a pair of Sentinel-1 TOPSAR IW data with the SNAP S1 TOPS-IW Interferometric processor. 
SNAP (SeNtinel’s Application Platform) [#f1]_ is the common architecture for all Sentinel Toolboxes jointly developed by Brockmann Consult, Array Systems Computing and C-S. The interferometric processing chain for Sentinel 1 TOPSAR IW images is implemented through the tools contained in the Sentinel-1 Toolbox.

This tutorial is referred to the service build V1.5.2

The interferometric SAR technique
---------------------------------

Interferometric synthetic aperture radar (InSAR) exploits the phase difference between two complex radar SAR observations taken from slightly different sensor positions and extracts information about the earth’s surface. A SAR signal contains amplitude and phase information. The amplitude is the strength of the radar response and the phase is the fraction of one complete sine wave cycle (a single SAR wavelength). The phase of the SAR image is determined primarily by the distance between the satellite antenna and the ground targets. By combining the phase of these two images after coregistration, an interferogram can be generated whose phase is highly correlated to the terrain topography. The InSAR technique can potentially measure millimetre-scale changes in deformation over spans of days to years. It has applications for geophysical monitoring of natural hazards, for example earthquakes, volcanoes and landslides, and in structural engineering, in particular monitoring of subsidence and structural stability.

Sentinel-1 Interferometric Wide Swath Products
----------------------------------------------

The Interferometric Wide (IW) swath mode is the main acquisition mode over land for Sentinel-1. It acquires data with a 250 km swath at 5 m by 20 m spatial resolution (single look). IW mode captures three sub-swaths using Terrain Observation with Progressive Scans SAR (TOPSAR). With the TOPSAR technique, in addition to steering the beam in range as in ScanSAR, the beam is also electronically steered from backward to forward in the azimuth direction for each burst, avoiding scalloping and resulting in homogeneous image quality throughout the swath. TOPSAR mode replaces the conventional ScanSAR mode, achieving the same coverage and resolution as ScanSAR, but with a nearly uniform SNR (Signal-to-Noise Ratio) and DTAR (Distributed Target Ambiguity Ratio). IW SLC products contain one image per sub-swath and one per polarisation channel, for a total of three (single polarisation) or six (dual polarisation) images in an IW product. Each sub-swath image consists of a series of bursts, where each burst has been processed as a separate SLC image. The individually focused complex burst images are included, in azimuth time order, into a single sub-swath image with black-fill demarcation in between, similar to ENVISAT ASAR Wide ScanSAR SLC products.


The processing service code is available in the GitLab repository `geohazards-tep/rss-snap-s1-insar <https://gitlab.com/geohazards-tep/rss/applications/dcs-rss-snap-s1-insar>`_.

Select the processing
=====================

* Login to the platform (see :doc:`user <../community-guide/user>` section)
<commit_msg>Update rss_snap_s1_insar.rst<commit_after>SNAP-InSAR – SNAP Sentinel-1 IW SLC Interferogram and Displacements
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

.. image:: assets/tuto_snap_s1_insar_icon.png
        
**SNAP-InSAR – SNAP Sentinel-1 IW SLC Interferogram and Displacements**

This service provides the interferometric processor for the Sentinel-1 TOPSAR IW SLC data performed through SNAP. SNAP is a common architecture for all Sentinel Toolboxes, which is ideal for Earth Observation processing and analysis.

**EO sources supported**:

    - Sentinel-1 TOPSAR IW SLC

**Output specifications**

The service provides 3 output products.

+-------------------------------+---------------------------------------------------------------------------------------------------------------+
| Output-1 - Coherence product                                                                                                                  |
+===============================+===============================================================================================================+
| Correspondent file            | Coherence product                                                                                             |
+-------------------------------+---------------------------------------------------------------------------------------------------------------+
| Information types             | Interferometric Coherence computed on input SLC couple                                                        |
+-------------------------------+---------------------------------------------------------------------------------------------------------------+
| Raster format                 | GeoTIFF                                                                                                       |
+-------------------------------+---------------------------------------------------------------------------------------------------------------+
| resolution                    | Native or User selection                                                                                      |
+-------------------------------+---------------------------------------------------------------------------------------------------------------+
| Projection types              | EPSG:4326 - WGS84                                                                                             |
+-------------------------------+---------------------------------------------------------------------------------------------------------------+
| Bit depth                     | Float 32                                                                                                      |
+-------------------------------+---------------------------------------------------------------------------------------------------------------+
| Processing Level              | L2                                                                                                            |
+-------------------------------+---------------------------------------------------------------------------------------------------------------+
| Physical product available    | YES                                                                                                           |
+-------------------------------+---------------------------------------------------------------------------------------------------------------+
| Browse product available      | YES (Both PNG and GeoTIFF)                                                                                    |
+-------------------------------+---------------------------------------------------------------------------------------------------------------+
| Output Filename example       | coh_VV_18Oct2020_30Oct2020 											|   
+-------------------------------+---------------------------------------------------------------------------------------------------------------+

|

+-------------------------------+---------------------------------------------------------------------------------------------------------------+
| Output-2 – Phase product                                                                                                                      |
+===============================+===============================================================================================================+
| Correspondent file            | Phase product                                                                                                 |
+-------------------------------+---------------------------------------------------------------------------------------------------------------+
| Information types             | Interferometric Phase computed on input SLC couple                                                            |
+-------------------------------+---------------------------------------------------------------------------------------------------------------+
| Raster format                 | GeoTIFF                                                                                                       |
+-------------------------------+---------------------------------------------------------------------------------------------------------------+
| resolution                    | Native or User selection                                                                                      |
+-------------------------------+---------------------------------------------------------------------------------------------------------------+
| Projection types              | EPSG:4326 - WGS84                                                                                             |
+-------------------------------+---------------------------------------------------------------------------------------------------------------+
| Bit depth                     | Float 32                                                                                                      |
+-------------------------------+---------------------------------------------------------------------------------------------------------------+
| Processing Level              | L2                                                                                                            |
+-------------------------------+---------------------------------------------------------------------------------------------------------------+
| Physical product available    | YES                                                                                                           |
+-------------------------------+---------------------------------------------------------------------------------------------------------------+
| Browse product available      | YES (Both PNG and GeoTIFF)                                                                                    |
+-------------------------------+---------------------------------------------------------------------------------------------------------------+
| Output Filename example       | phase_VV_18Oct2020_30Oct2020 											|
+-------------------------------+---------------------------------------------------------------------------------------------------------------+

|

+-------------------------------+---------------------------------------------------------------------------------------------------------------+
| Output-3 – Displacement product                                                                                                               |
+===============================+===============================================================================================================+
| Correspondent file            | Displacement product                                                                                          |
+-------------------------------+---------------------------------------------------------------------------------------------------------------+
| Information types             | Line of sight displacement                                                                                    |
+-------------------------------+---------------------------------------------------------------------------------------------------------------+
| Raster format                 | GeoTIFF                                                                                                       |
+-------------------------------+---------------------------------------------------------------------------------------------------------------+
| resolution                    | Native or User selection                                                                                      |
+-------------------------------+---------------------------------------------------------------------------------------------------------------+
| Projection types              | EPSG:4326 - WGS84                                                                                             |
+-------------------------------+---------------------------------------------------------------------------------------------------------------+
| Bit depth                     | Float 32                                                                                                      |
+-------------------------------+---------------------------------------------------------------------------------------------------------------+
| Processing Level              | L2                                                                                                            |
+-------------------------------+---------------------------------------------------------------------------------------------------------------+
| Physical product available    | YES                                                                                                           |
+-------------------------------+---------------------------------------------------------------------------------------------------------------+
| Browse product available      | YES (Both PNG and GeoTIFF)                                                                                    |
+-------------------------------+---------------------------------------------------------------------------------------------------------------+
| Output Filename example       | displacement_VV_18Oct2020_30Oct2020 										|
+-------------------------------+---------------------------------------------------------------------------------------------------------------+

.. NOTE::

    - the "Browse GeoTIFF" product is always a GeoTIFF file with the same resolution of the physical product, with Uint8 bit depth and projection EPSG:3857.
    - The “Browse PNG” product is always a PNG file with the same resolution of the physical product, with Uint8 bit depth.


-----

This tutorial processes a pair of Sentinel-1 TOPSAR IW data with the SNAP S1 TOPS-IW Interferometric processor. 
SNAP (SeNtinel’s Application Platform) [#f1]_ is the common architecture for all Sentinel Toolboxes jointly developed by Brockmann Consult, Array Systems Computing and C-S. The interferometric processing chain for Sentinel 1 TOPSAR IW images is implemented through the tools contained in the Sentinel-1 Toolbox.

This tutorial is referred to the service build V1.8.3

The interferometric SAR technique
---------------------------------

Interferometric synthetic aperture radar (InSAR) exploits the phase difference between two complex radar SAR observations taken from slightly different sensor positions and extracts information about the earth’s surface. A SAR signal contains amplitude and phase information. The amplitude is the strength of the radar response and the phase is the fraction of one complete sine wave cycle (a single SAR wavelength). The phase of the SAR image is determined primarily by the distance between the satellite antenna and the ground targets. By combining the phase of these two images after coregistration, an interferogram can be generated whose phase is highly correlated to the terrain topography. The InSAR technique can potentially measure millimetre-scale changes in deformation over spans of days to years. It has applications for geophysical monitoring of natural hazards, for example earthquakes, volcanoes and landslides, and in structural engineering, in particular monitoring of subsidence and structural stability.

Sentinel-1 Interferometric Wide Swath Products
----------------------------------------------

The Interferometric Wide (IW) swath mode is the main acquisition mode over land for Sentinel-1. It acquires data with a 250 km swath at 5 m by 20 m spatial resolution (single look). IW mode captures three sub-swaths using Terrain Observation with Progressive Scans SAR (TOPSAR). With the TOPSAR technique, in addition to steering the beam in range as in ScanSAR, the beam is also electronically steered from backward to forward in the azimuth direction for each burst, avoiding scalloping and resulting in homogeneous image quality throughout the swath. TOPSAR mode replaces the conventional ScanSAR mode, achieving the same coverage and resolution as ScanSAR, but with a nearly uniform SNR (Signal-to-Noise Ratio) and DTAR (Distributed Target Ambiguity Ratio). IW SLC products contain one image per sub-swath and one per polarisation channel, for a total of three (single polarisation) or six (dual polarisation) images in an IW product. Each sub-swath image consists of a series of bursts, where each burst has been processed as a separate SLC image. The individually focused complex burst images are included, in azimuth time order, into a single sub-swath image with black-fill demarcation in between, similar to ENVISAT ASAR Wide ScanSAR SLC products.


The processing service code is available in the GitLab repository `geohazards-tep/rss-snap-s1-insar <https://gitlab.com/geohazards-tep/rss/applications/dcs-rss-snap-s1-insar>`_.

Select the processing
=====================

* Login to the platform (see :doc:`user <../community-guide/user>` section)

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