SNAP in a Nutshell

Andrea Minchella (andrea.minchella@sa.catapult.org.uk)

21-22/01/2016 – “ESA SNAP-Sentinel-1 Training Course”

Satellite Applications Catapult - Electron Building, Harwell, Oxfordshire

SNAP in a Nutshell

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What is SNAP?

Credit: SNAP – The Sentinels Application Platform @ ESA EO SCIENCE 2.0 Workshop, 12-14 October 2015, ESA-Esrin, Frascati, Rome (Italy)

SNAP in a Nutshell

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Sentinel Toolboxes Consortia

Credit: SNAP – The Sentinels Application Platform @ ESA EO SCIENCE 2.0 Workshop, 12-14 October 2015, ESA-Esrin, Frascati, Rome (Italy)

SNAP in a Nutshell

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Toolbox Evolution

Credit: SNAP – The Sentinels Application Platform @ ESA EO SCIENCE 2.0 Workshop, 12-14 October 2015, ESA-Esrin, Frascati, Rome (Italy)

SNAP in a Nutshell

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Toolbox Evolution

Credit: SNAP – The Sentinels Application Platform @ ESA EO SCIENCE 2.0 Workshop, 12-14 October 2015, ESA-Esrin, Frascati, Rome (Italy)

SNAP in a Nutshell

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Architecture Highlights

• Java, Python implementation

• Snap desktop: integrated graphical user-friendly interface;

• Snap engine (Graph Processing Tool): core and command line

interface;

• Graphical or command-line execution;

• Tiled memory management for working with very large data

products;

• Data abstraction models to handle all SAR missions in a common

way

• Modular design for easy modifications and upgrades

• Users are able to add their own modules via APIs

• Multithreading and Multi-core processor support

• Integrated WorldWind visualisation

SNAP in a Nutshell

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Source Code Repository

Credit: Sentinel-1 Toolbox – Open Source Tools for EOScience 2.0 @ ESA EO SCIENCE 2.0 Workshop, 12-14 October 2015, ESA-Esrin, Frascati, Rome (Italy)

SNAP in a Nutshell

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Supported Platforms

• Windows (XP, Vista, 7, 8, 10)

• Linux

• Mac OS X

• 32 bit/64 bit

• Graphical User Interface

• Command-Line Interface

SNAP in a Nutshell

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Graph Processing Tool

Credit: SNAP – The Sentinels Application Platform @ ESA EO SCIENCE 2.0 Workshop, 12-14 October 2015, ESA-Esrin, Frascati, Rome (Italy)

SNAP in a Nutshell

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SNAP Applicaton Modes

Credit: SNAP – The Sentinels Application Platform @ ESA EO SCIENCE 2.0 Workshop, 12-14 October 2015, ESA-Esrin, Frascati, Rome (Italy)

SNAP in a Nutshell

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Multi-Sensor Support

Credit: SNAP – The Sentinels Application Platform @ ESA EO SCIENCE 2.0 Workshop, 12-14 October 2015, ESA-Esrin, Frascati, Rome (Italy)

SNAP in a Nutshell

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Generic Functions and Tools

Credit: SNAP – The Sentinels Application Platform @ ESA EO SCIENCE 2.0 Workshop, 12-14 October 2015, ESA-Esrin, Frascati, Rome (Italy)

SNAP in a Nutshell

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STEP (Science Toolbox Exploitation Platform)

Credit: SNAP – The Sentinels Application Platform @ ESA EO SCIENCE 2.0 Workshop, 12-14 October 2015, ESA-Esrin, Frascati, Rome (Italy)

https://step.esa.int EO Science collaborative platform

• SNAP software download

• SNAP tutorials and documentation

• Technical forum and community animation

• Gathering user feedback and usage

SNAP in a Nutshell

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Sentinel-1 Toolbox: evolution of NEST

https://earth.esa.int/web/nest/home/

Credit: Sentinel-1 Toolbox – Open Source Tools for EOScience 2.0 @ ESA EO SCIENCE 2.0 Workshop, 12-14 October 2015, ESA-Esrin, Frascati, Rome (Italy)

Classification: CATAPULT OPEN

Example of Sentinel-1 data processing

Sentinel-1 toolbox architecture: data flow

Snap desktop (GUI)

Integrated graphical user interface for SAR data visualisation, analysis and processing

Graph Processing Tool (GPT)

For command line execution of user-definedbatch processing chains

WritersReaders Generic Product Model (GPM)

Sentinel-1

ENVISAT ASAR

ERS-1&2

Radarsat-2

Cosmo-SkyMed

TerraSAR-X

Tandem-x

ALOS PALSAR1&2

Radarsat-1

JERS SAR

Beam dimap

Geotiff

Netcdf

Envi

Generic Binary

Google Earth

PolSARpro

etc

SNAP in a Nutshell

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Generic Functions and Tools

• Statistics & Data Analysis

• Metadata handling

• Subset, Resample and Band Arithmetic

• Export to GeoTiff, HDF 4 & 5, NetCDF, Bynary, Envi, Kmz formats

• LUT and Layer Management

• ROI tools, layer stacking

• ….

SNAP in a Nutshell

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SAR Functionality

• Left and right facing missions displayed by start time and near range

• Absolute calibration

• Multilooking

• speckle (single and multitemporal) filtering

• Precise orbit handling (Doris, Prare and Delft orb.)

• Coregistration of detected and complex products

• Debursting of ASAR WSS

• Range-Doppler Terrain Correction

• Radiometric normalization during Terrain Correction

• SAR simulation

• Layover and shadow masks

• Simulated SAR Terrain Correction

• Ellipsoid correction, Map Reprojection, Mosaicking

• Automatic DEM download and tile selection

• Product library for scanning and cataloguing large archives efficiently

SNAP in a Nutshell

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SAR Functionality

• Ocean tools: basic routines for oil spill detection, ship detection and wind field

estimation from SAR data

• Inteferometry for Strimap and Zero-Doppler focused data

• Compatibility with ESA PolSARpro Toolbox (Reader, Writer)

Level of support depends on sensor & product type. Please refer to documentation for full

details such as the Operators help

But useful also to consult the “Supported_Products&MainTools.xls” available in the

Documentation page on NEST website https://earth.esa.int/web/nest/home/

SNAP in a Nutshell

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InSAR

Architecture Highlights

• Coregistration and resampling

• DEM assisted coregistration

• Products: interferogram and coherence

• Filtering: both spectral and phase

• Geo-coding

• Unwrapping via 3rd party sw(SNAPHU)

• Phase to height conversion

• Differential InSAR

• Cross InSAR (ERS-ENVISAT)

Only zero doppler and strip map

data are fully supported

SNAP in a Nutshell

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Ocean Tools

Land Masked Detection Map Projected

• Object (ship) Detection

• Oil Spill Detection

• Wind Field Estimation

• Create Land Mask

SNAP in a Nutshell

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New Sentinel-1 Functionality

• Calibration

• Thermal Noise Removal

• Slice Assembly

• TOPSAR Deburst and Merge

• GRD Border Noise Removal

• TOPSAR Interferometry

SNAP in a Nutshell

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New Level-2 OCN Visualisation

Credit: Sentinel-1 Toolbox – Open Source Tools for EOScience 2.0 @ ESA EO SCIENCE 2.0 Workshop, 12-14 October 2015, ESA-Esrin, Frascati, Rome (Italy)

SNAP in a Nutshell

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Polarimetric Tools

Quad Pol Decompositions• Sinclair • Pauli • Freeman-Durden • Van Zyl• Yamaguchi • Cloude • H/A Alpha • Touzi

Dual Pol Decomposition • H/A Alpha

SNAP in a Nutshell

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Quad Pol & Dual Pol Functionality

Credit: SNAP – The Sentinels Application Platform @ ESA EO SCIENCE 2.0 Workshop, 12-14 October 2015, ESA-Esrin, Frascati, Rome (Italy)

SNAP in a Nutshell

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The Product Library

• Convenient browsing and importing of products

having information and Quick Look product

• Now handles optical products and S-1 L2 OCN

products

SNAP in a Nutshell

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Processing Environment (in this course)

• Virtual Machine [4 cores (2 Ghz), 64 GB Ram], over Catapult cloud

computing commercial CEMS (Climate, Environment and Monitoring

from Space - CEMS)

• OS VM: Linux Ubuntu 14.04

N.B: Worldwind does not work sometimes om Linux and Mac OS.

• Snaphu (phase unwrapping) runs over Linux

Classification: OPEN

SNAP in a Nutshell

CEMS: Climate and Environmental Monitoring from Space

A purpose-built High Performance Cloud Computing facilities to provide:

• access to a wide range of Climate, Earth Observation (EO) and non-EO data;

• on demand, flexible, scalable and secure infrastructure for all communities

interested in working with satellite derived data and applications.

Classification: OPEN

SNAP in a Nutshell

Processing Environment (in this course)

• Guide to access the CEMS Commercial Cloud VM your desk

After logging in the VM:

• To launch SNAP GUI:

1. Double click over SNAP icon on the desktop

2. From Terminal: write command below into a terminal

sh /mnt/data/snapv2_20112015/bin/snap

• To launch the SNAP Graph Processing Tool (GPT) available only from terminal

Write command below into a terminal:

sh /mnt/data/snapv2_20112015/bin/gpt

SNAP in a Nutshell

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Customisation of “.snap” folder

By the default SNAP creates a folder named “.snap" during

the installation.

This folder contains internal configuration files (colour maps,

graphs etc.) and auxiliary files such as DEM, Orbits etc.

downloaded during the processing.

By default the .snap folder is created into:

• “home” directory (Linux-Mac)

• “C:\Users\user_name\” directory (Windows)

Because the ".snap" is starting with ".“, the folder is not always visible,

and also it is convenient having it in a partition where there is free space.

SNAP in a Nutshell

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Configuration of SNAP

Renaming and change the location for the .snap folder

Look for into the snap installation folder "../snap/etc/“

• Edit and modify into the “snap.properties” file the following:

snap.home=/mnt/data/snapv2_20112015/

snap.userdir=/mnt/data/logsnap

• Edit and modify into “../snap/etc/snap.conf” file (this for GPT):

default_userdir=/mnt/data/logsnap

Now the “.snap” folder is named “logsnap”

and it is located in: /mnt/data/logsnap

SNAP in a Nutshell

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SNAP interface

SNAP in a Nutshell

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SNAP interface: File

SNAP in a Nutshell

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SNAP interface: Edit

SNAP in a Nutshell

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SNAP Interface: Toolbars customisation

SNAP in a Nutshell

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SNAP Interface: Tool Windows

Worldwind requires OPEN GL library and it can

happen that some graphic card do not have it

or some version of Linux or Mac do not support

the application properly.

Use World map instead (click over it)

SNAP in a Nutshell

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SNAP Interface: Layer

SNAP in a Nutshell

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SNAP Interface: Vector

SNAP in a Nutshell

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SNAP Interface: Raster

SNAP in a Nutshell

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SNAP Interface: Optical

SNAP in a Nutshell

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SNAP Interface: Radar

SNAP in a Nutshell

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SNAP Interface: Tools

SNAP in a Nutshell

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SNAP Interface: Help

Any Question?