3.4.3.1. ASTER

_images/aster_tab.jpg

aster_tool ASTER

This tab allows for the conversion of ASTER L1T images to the physical measure of Top Of Atmosphere reflectance (TOA), or the application of a simple atmospheric correction using the DOS1 method (Dark Object Subtraction 1), which is an image-based technique (for more information about conversion to TOA and DOS1 correction, see Image conversion to reflectance).

Once the input is selected, available bands are listed in the metadata table.

3.4.3.1.1. ASTER conversion

  • Select file ASTER L1T open_file: select an ASTER image (file .hdf);
  • checkbox Apply DOS1 atmospheric correction: if checked, the DOS1 Correction is applied to all the bands;
  • checkbox Use value as NoData input_number: if checked, pixels having NoData value are not counted during conversion and the DOS1 calculation of DNmin; it is useful when image has a black border (usually pixel value = 0);
  • checkbox Create Band set and use Band set tools: if checked, bands are added to the active Band set after the conversion; also, the Band set is processed according to the tools checked in the Band set;
  • checkbox Add bands in a new Band set: if checked, bands are added to a new empty Band set after the conversion;

3.4.3.1.2. Metadata

All the bands found in the Select file ASTER L1T are listed in the table Metadata. For information about Metadata fields visit the ASTER page .

  • Date input_text: date of acquisition (e.g. 20130415);
  • Sun elevation input_number: Sun elevation in degrees;
  • Earth sun distance input_number: Earth Sun distance in astronomical units (automatically calculated if Date is filled;
  • UTM zone input_text: UTM zone code of the image;
  • UPPERLEFTM input_text: coordinates of the upper left corner of the image;
  • LOWERRIGHTM input_text: coordinates of the lower right corner of the image;
  • remove: remove highlighted bands from the table Metadata;
  • input_table : table containing the following fields;
    • Band: band name;
    • UnitConversionCoeff: value for radiance conversion;
    • PixelSize: solar irradiance of band;
  • BATCH batch_tool: add this function to the Batch;
  • RUN run: select an output directory and start the conversion process; only bands listed in the table Metadata are converted; converted bands are saved in the output directory with the prefix RT_ and automatically loaded in QGIS;