| CHRIS/Proba Extract Features | |
The Extract Features Tool is used to extract surface and atmospheric features from CHRIS images. Before you can perform the Feature Extraction on the CHRIS product, you have to apply the TOA Reflectance Computation first.
The measured spectral signature depends on the illumination, the atmosphere, and the sur- face. The figure below shows CHRIS Mode 1 band locations compared with the spectral curve of healthy vegetation, bare soil, and the atmospheric transmittance. The spectral bands free from atmo- spheric absorptions contain information about the surface reflectance, while others are mainly affected by the atmosphere.
At this step, rather than working with the spectral bands only, physically-inspired features are extracted in order to increase the separability of clouds and surface covers. These features are extracted independently from the bands that are free from strong gaseous absorptions, λi ⊂ BS, and from the bands affected by the atmosphere, λi ⊂ BA. A detailed analysis of the extracted features can be found in the ATBD.
The Extract Features tool can be invoked from VISAT Tools menu by selecting the Extract Features command in the CHRIS/Proba Tools submenu.
Selecting the Extract Features command brings up following dialog :
Name: Here the user specifies the source product. The combo box presents a list of all products open in VISAT. The user may select one of these or, by clicking on the button next to the combo box, choose a product from the file system.
Name: Used to specify the name of the target product.
Save as: Used to specify whether the target product should be saved to the file system. The combo box presents a list of file formats, currently BEAM-DIMAP, GeoTIFF, and HDF5. The text field allows to specify a target directory.
Open in VISAT: Used to specify whether the target product should be opened in VISAT. When the the target product is not saved, it is opened in VISAT automatically.
Run Creates the target product. The processing is actually deferred until the target band data are accessed, either by writing the product to the file system or by viewing the band data. When the Save as option is checked, the processing is triggered automatically.
Close Closes the dialog.
Help Displays this page in VISAT Help.