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IAVISA Software Tools

Architecture

The main requirements for the architecture of the IAVISA software are
  • let a single human sample collector efficiently collect classified IAVISA footprints
  • store samples comprising classification and auxiliary data persistently in a database
  • export the data in the database to a simple output format
Most of the IAVISA software components are realized as BEAM/VISAT plug-ins, such as the AVHRR reader and the sample selection tool.
A tool used to analyse and export the database is independently developed from the BEAM interfaces. It is run stand-alone.


The auxiliary data used by the system are the Köppen climatology and a IGBP surface type global maps.
They are used by the sample selection tool to automatically pre-classify each a pixel while an operator moves the mouse cursor over an AVHRR image.
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METOP/AVHRR Reader

The METOP/AVHRR reader enables VISAT to import METOP/AVHRR Level-1B data products into the BEAM product model, which is a prerequisite for the visualisation and the further analysis of pixel data in VISAT.

In summary, the reader exhibits the following features:
  • Reading of tie-point geometry data, usage of interpolated geometry data for pixels not located at tie-points
  • On-the-fly conversion of raw counts into geophysical values
  • Automatic detection of channel 3a and 3b usage

Note that the METOP/AVHRR reader only considers pixels which geographical positions can be determined without extrapolating the tie-point grids: The nominal AVHRR scan line exhibits 2048 pixels with either 51 (low resolution) or 103 (high resolution) tie points, which start at pixel number 25 or 5 and are sampled at intervals of 40 and 20 pixels, respectively.
All pixels before the first and after the last tie-point in an image row are not considered by the AVHRR reader.

User Interface

The AVHRR/3 reader plug-in does not have a specific user interface, it simply plugs into the VISAT file import menu:


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After importing the AVHRR L1b product in VISAT the following contents is shown in the VISAT’s Product View:



Images from AVHRR bands can now be displayed.


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