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Processing Aster Data for Atmospheric Correction

PCI Geomatics -

The Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) sensor is part of five sensor systems on board Terra. Terra is a satellite that was launched on December 18, 1999 at Vandenberg Air Force Base, California, USA. ASTER is unique in that it offers nearly simultaneous capture of stereo images, minimizing temporal changes and sensor modeling errors. Its data is used in a wide array of global change related applications, including vegetation, geology and soil, climatology and the creation of digital elevation models.

ASTER has 14 bands of information consisting of visible near infrared (VNIR), short wave infrared (SWIR) and thermal infrared (TIR). PCI Geomatica supports ASTER Level 1A and 1B data in .HDF format. Although both formats are supported we recommend the use of Level 1A to obtain the highest accuracy.

The following tutorial demonstrates how to process ASTER data in Geomatica Focus before using it in the atmospheric correction (ATCOR) GUI. The following steps must be taken in order for the ATCOR GUI to automatically populate with all of the correct metadata imported from the ASTER data.


Raw Imagery

To view the raw imagery in Focus you will need to select the .hdf file associated with the data.

Focus will then prompt you to select which band you would like to open. Any band can be selected for viewing purposes.



In order to use the imagery for ATCOR processing it will need to be imported using CDASTER followed by the Data Merge Wizard

1. In Focus select Tools > Algorithm Librarian...

2. Find CDASTER and click Open...

3. CDASTER will need to be run 4 different times to create 4 separate .PIX files using the following band order 1,2,31 - 32  - 4,5,6,7,8,9  - 10,11,12,13,14.

4. From the Files tab select the same output file name and location for Output: Satellite CD Layer(s), OutputOrbit: Satellite Orbital Ephemeris Layer and OutputGCP: Output GCP Layer.

5. Click on Input Params 1 tab

6. Select the .hdf file for your data.

7. Input 1,2,31 in the CD Input Layer(s) List (Max. 16).

8. Run CDASTER 3 more times. Make sure to change the output file name and location for each file and change the CD Input Layer(s) to the following:  1,2,31 - 32  - 4,5,6,7,8,9  - 10,11,12,13,14.

9. Click Run.


Image examples:

CD Input Layer(s): 1,2,31


CD Input Layer(s): 32


CD Input Layer(s):  4,5,6,7,8,9


CD Input Layer(s): 10,11,12,13,14


Data Merge

After all of the bands have been imported to .PIX using CDASTER, the SWIR and VNIR bands will need to be merged into one .PIX file for use in ATCOR.

1. In Focus click on Tools > Data Merge...

2. Select bands 1,2,31,4,5,6,7,8,9.

3. Select an output file name and location.

4. Adjust the Geo-referencing Setup parameters and click Next.

5. Verify the Selected Layers.

6. Click Finish.


Atmospheric Correction

The file created using the Data Merge Wizard can now be used in ATCOR as it contains both the SWIR and VNIR data.

1. In Focus click on Analysis > Atmospheric Correction > Top of the Atmospheric Reflectance...

2. Select the data merge .pix file as the Multispectral file. All of the necessary parameters will then automatically populate.

3. When prompted for a Thermal Image in ATCOR – Surface temperature select the CDASTER .pix file for bands 10,11,12,13,14 (TIR).


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