1.2.1 Software Tools

1.2.1.1 General Software Tools

The EnviView tool, which is discussed in detail in the ENVISAT Handbook, can also be used to convert ENVISAT data into hdf files. As briefly discussed in the next section, "EnviView," 1.2.1.2. this ENVISAT tool is not intended for the detailed analysis, visualisation, and processing of ENVISAT data. Other commercial and proprietary tools provide these facilities in great detail and with many specialised options. The difference between such tools and EnviView is that they are usually aimed at certain classes of data, such as images or atmospheric data, or even data for a particular instrument. EnviView, however, is a single solution for all ENVISAT products. EnviView is intended as a stepping stone between these tools and the proprietary data format used for ENVISAT data. The data can then be automatically read by any software supporting this format.

Some other tools that may be used for more detailed analysis are provided below. Some are not ASAR specific.

• IDL (Interactive Data Language) http://www.rsinc.com a general purpose graphical and scientific computing system
• CAESAR image processing (speckle reduction) from NAS Software at http://www.nasoftware.co.uk
• DORIS Insar software (open-source) at http://www.geo.tudelft.nl/fmr/research/insar/sw/doris/index.html.cgi
• Earthview InSAR from PGI Geomatics at http://www.pcigeomatics.com
• ENVI from Research Systems at http://www.rsinc.com based on the IDL product
• ERS SAR toolbox described at http://esapub.esrin.esa.it/eoq/eoq64/toolbox.pdf and available at http://earth.esa.int/STBX/
• GAMMA http://www.gamma-rs.ch sells modular SAR processor software, and interferometric SAR and differential SAR processors
• GEOimage http://www.geoimage.fr software for processing Earth-observation imagery
• Geomatica (remote-sensing image processing, cartography, photogrammetry) http://www.pcigeomatics.com
• IMAGINE Professional (remote sensing scene analysis, radar analysis, mapping) http://www.erdas.com
• Matlab http://www.mathworks.com includes a number of optional toolboxes including Signal Processing, System Identification, Fuzzy Logic, Image Processing, Mapping, Neural Networks.
  
• Mathematica http://www.wolfram.com/
  
• Noesys (data exploration and visualisation) from Research Systems http://www.rsinc.com
• PulSAR from Phoenix Systems, http://www.phoenixsystems.co.uk
  
• PV-WAVE http://www.vni.com data manipulation, visualisation, statistics. Image Processing and Signal Processing toolkits available.
• SARscape http://www.sarmap.ch

1.2.1.2 EnviView

As with the data from all of the ENVISAT instruments, the EnviView is a simple tool to provide a first look at ASAR data files in the PDS format. It uses a graphical user interface for data exploration and visualisations and is intended for the following purposes:

• To be able to open any Level 0, 1b, Level 2 or auxiliary PDS data file.
  
• To determine and display the contents of a file and the value of any given fields in any data set, except raw source packets (level 0 data).
  
• To provide basic visualisation of data through simple 2D graphs and images.
  
• To visualise certain high level data sets in a meaningful manner where a 2D graph conveys little information,especially:
  
  • ASAR image data sets
    
  • ASAR Wave spectra.
    
• To provide a representation of the geographic coverage on a rectangular map projection.
  
• To export selected data to HDF, ASCII or binary data files, for analysis in COTS tools such as Mathematica, IDL, Excel, and so on..
  
• To save the contents of a record as HTML text for inclusion in reports.
  
• To provide support for printing and system clipboard (cut/paste)where possible.
  
• To be highly portable and to reach as wide an audience as possible.
  
• To be guaranteed to run on Unix,Windows and MacOS and potentially other platforms too.

Figure 1.101 Example of Level 1B Wave Product Cross Spectra

Figure1.101 is an example of a level 1b wave product, as seen using the EnviView ASAR Wave Spectra View window. (See section entitled Wave Spectra 1.1.5.5. ). A wave spectrum viewer displays a false colour polar plot showing level 1B or level 2 ASAR wave spectra data. Since the data values are complex, having both real and imaginary parts, various representations of the spectra are possible. Data from one record at a time is displayed with the option of displaying record data sequentially as a movie.

The ASAR level 1B wave spectrum data is complex, containing both real and imaginary parts. EnviView only displays scalar (1 dimensional) values on the ASAR wave spectrum viewer, which means that it can only display either the real parts, the imaginary parts, or some scalar combination of the real and imaginary parts.

ASAR Level 2 data is not complex, hence there is no need to have selection provided for different display types when viewing such a data set. Level 2 data is neither symmetric nor anti-symmetric, and contains information for the entire 360 spectrum.

The complete instructions for the use and application of the EnviView viewer are provided in the EnviView User Guide that is included with the viewer when it is delivered to the customer.

1.2.1.3 ASAR Toolbox

The Basic Envisat SAR Toolbox (BEST) is a collection of executable software tools that has been designed to facilitate the use of ESA SAR data. The purpose of the Toolbox is not to duplicate existing commercial packages, but to complement them with functions dedicated to the handling of SAR products obtained from ASAR (Advanced Synthetic Aperture Radar) and AMI (Active Microwave Instrument) onboard Envisat and ERS 1&2 respectively.

The Toolbox operates according to user-generated parameter files. The software is designed with an optional graphical interface that simplifies specification of the required processing parameters for each tool and (for Windows versions only) sets it running.

The tools are designed to achieve the following functions:

• Data Import and Quick Look: generation of quick-look and full resolution internal format files from a variety of ESA SAR products and import of TIFF and GeoTIFF images and generic raster data.
• Data Export: output of data to selected common formats (TIFF, Geo TIFF and BIL).
• Data Conversion: conversion between different image formats (e.g. power to amplitude) and transformation of the data by flipping or slant range to ground range reprojection.
• Statistical: calculation of global or local statistical parameters from real image data and computation of the principal components of multiple images. Resampling: over- and under- sampling of an image by means of spatial and spectral methods.
• Co-registration and Coherence Generation: automatic co-registration of both real and complex images, calculation of interferometric coherence and application of automatic geo-correction.
• Radiometric Resolution Enhancement: improvement of the radiometric resolution of a backscatter image.
• Calibration: radiometric correction of an input image to a variety of levels.

The Toolbox has been designed to handle ESA data products from both the Envisat ASAR instrument and the AMIs on ERS 1&2.

ASAR data acquired in Image Mode, Wide Swath Mode, Alternating Polarisation Mode and Global Monitoring Mode, processed to Level 0 or Level 1b (SLC, Precision, Medium Resolution or Ellipsoid Geo-coded), is supported.

Image Data from ERS SAR, processed as RAW, SLC, SLCI, PRI, GEC or GTC, is also supported.

The Toolbox handles the standard Envisat product file format. For ERS data, products generated within the ESA ERS ground segment at D-PAF, I-PAF, UK-PAF and ESRIN are supported, plus data from non-ESA PAF stations, if they are delivered with ESA CEOS annotations.

More information is available from the envisat web site at http://envisat.esa.int/best