Processing and exploiting RADAR data with ENVI SARscape software
Part 1 – Introducing ENVI SARScape
I. Introducing ENVI SARscape
SARscape is a set of specialized modules developed and run on the ENVI software platform of Exelis VIS (currently part of Harris Group – USA). ENVI SARScape includes a diverse set of tools specializing in processing and analyzing Radar/SAR (Synthetic Aperture Radar) data combined with ENVI’s outstanding image processing features to allow monitoring changes, creating DEMs and mapping displacement… The latest version is ENVI SARscape 5.3, officially released by the company on February 12, 2016.
ENVI SARscape specializes in analyzing and processing many types of Radar/SAR data captured from satellites and aircraft, with technical features that allow users to process and interpret ambiguous Radar/SAR data into meaningful information appropriate to the context.
II. Modules in ENVI SARscape
After installation, ENVI SARSscape will be integrated into the general interface of ENVI software in the Tools folder tree. A complete SARscape set will include the following modules and utility tools:
1) Basic Module: The basic SARSscape module allows reading and processing radar image data such as advanced filtering, image correction and merging, creating multi-look images… to image classification processing, object recognition or movement tracking… – functions for processing SAR data (satellite and aircraft) based on intensity and coherence values.
2) Focusing Module: Supports focusing on preprocessing of data types: ERS-1/2 SAR, JERS-1 SAR, ENVISAT ASAR and ALOS PALSAR-1.
3) Gamma & Gaussian Filter Module: Includes a set of specialized filtering tools for different types of SAR data, used to filter, remove noise while preserving radar wave reflection, structural properties and spatial resolution of the image.
4) Interferometry Module: Provides tools for processing interferometric SAR data, including InSAR data processing techniques (Interferometric SAR) to create DEM, create correlation images (Coherence); and DInSAR (Differential Interferometric SAR) techniques to map displacement and monitor surface deformation (Displacement/ Deformation maps) to update topographic, geomorphological and landslide maps…
5) ScanSAR Interferometry Module: Provides tools to process InSAR and DInSAR data covering large areas.
6) Interferometric Stacking Module: Based on Small Baseline Subset (SBAS) and Persistent Scatterers (PS) techniques to detect the displacement of single objects, using a multi-temporal SAR image dataset.
7) SAR Polarimetry / Polarimetric Interferometry Module: Supports the processing of polarized SAR and polarized interferometric SAR data.
8) Quality Assessment Tools: includes a set of tools used to evaluate the quality of SAR data in terms of geometry, radiation and polarization.
III. Overview of radar remote sensing applications with ENVI SARscape
Radar remote sensing is remote sensing using ultra-high frequency radiation (>1mm) that allows observing objects at all times of the day and in all weather conditions. Therefore, radar satellite images obtained are independent of weather conditions (cloud cover), atmosphere, etc. and images are taken both day and night. This is an extremely effective tool for monitoring and supervising resources and the environment. Not only that, because they are collected at much longer wavelengths than the usual visible wavelengths, radar satellite images are very sensitive to the characteristics of structure, roughness, uniformity and moisture of the ground surface, this information is almost not available on optical images.
With the development of Radar remote sensing and processing technology (such as ENVI SARScape, …), today Radar/SAR image data is increasingly widely used in many studies on terrestrial and ocean environments, mineral exploration, resource management … and especially in the assessment, monitoring and supervision of natural disasters (earthquakes, volcanoes, ice melting, floods, oil spills, …).
