Processing ASTER DATA using ENVI 4.1 Create a folder in your directory to store your raw data files. Also, create a separate folder for your processed data files.

The ASTER data will come in an .hdf file (Hierarchical Data Format) and .met file (ASCII metadata files). The .met file is the data header. Keep both. A break-down for the file naming conventions can be found at http://edcdaac.usgs.gov/landdaac/tools/heg/heg_summary.asp

Unprocessed ASTER data files need to go through File Map Projection Conversion to set the projection so they can be read by the ArcGIS software.

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From the Start Menu (or the Desktop Icon) open ENVI 4.1

The ENVI toolbar opens at the top of your screen.

1. Select File > Open External File > EOS > ASTER.

2. When the file selection dialog appears, select the input file.

ENVI automatically extracts the header information, including any georeferencing information, and enters the image bands into the Available Bands List.

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Processing instructions for a (Single file): Using (Look In) box navigate to your data folder, highlight file to be processed, left click Open button. Dialog box (Available Bands List) displays. Use default settings and left click on Load RGB button.

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An image display group in ENVI consists of three different image windows: a Main Image window, a Zoom window, and a Scroll window. The bounding box indicates a region of interest. The bounding box in the Scroll window controls the image display in the Main window and the Main window bounding box controls the image in the Zoom window. The Zoom window provides you with virtually unlimited zoom capabilities such as zooming in or out and panning. (Description from Online Help)

A detailed description about each window can be found in ENVI’s Online Help.

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On the ENVI Toolbar, left Click on Basic Tools to get to Layer Stacking. Layer Stacking is used to build a new multiband file from georeferenced images of

various pixel sizes, extents, and projections. Read a detailed description about Layer Sacking in ENVI Online Help. Left Click on Layer Stacking to get to the Layer Stacking Parameters dialog box. Notice Output Map Projection is set at Arbitrary. Do not change setting at this point.

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Left click on Import File to get the Layer Stacking Input dialog box. In the Select Input File window, highlight the upper file. Verify the file information and click OK. Note: Some files may not contain proper Header file information. The Header information will need to be corrected before proceeding with the following steps. This brings you back, to the Layer Stacking Parameters dialog box, the next step is to set the Layer Stacking file’s Output Result to memory (all other values remain on default settings). Notice the projection has automatically been changed to UTM.

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Click OK. A warning dialog box opens; make sure to select Memory again and click OK. This will commence the auto-run of File Map Projection Conversion process. [Optional step: After the conversion has been completed, the Available Bands List dialog box will reappear. At this point you can click on Load RGB to view your file again or you can skip to the next processing step of converting the file to a TIFF/GeoTiff.]

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Saving Files to TIFF/GeoTIFF On the ENVI Toolbar, left Click on File to get to Save File As. This opens the menu of file choices. Scroll down to Tiff/GeoTIFF, left click to open the Output dialog box.

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Highlight the Memory 1 file and click OK.

The Output File to Tiff/GeoTiff dialog box is used to set the name and path for your image file.

Saving Output Files

1. Enter the output filename or use the Choose button to select the output filename.

2. Click OK when all options are correctly set.

This screen shot shows the default setting.

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To change the default output setting to your disk drive: On the ENVI Toolbar click File then select Preferences. In the Systems Preferences Dialog box select the Default Directories tab then click on the Choose button next to Output Directory. The Browse For Folder dialog box open, scroll to your drive and folder, then click OK.

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Or, in the box type your path to your folder. Shortcut Tip: In the Output Filename dialog box navigate to the folder containing your original data. Highlight your data file, click in the Filename box >move to the end of the line>backspace to remove the .hdf file extension.

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In the Look in box navigate to your (Processed) folder then click Open. This brings you back to the Output File to Tiff/GeoTiff dialog box with your path and name set to the correct storage folder. Click OK to start the output processing. Open folder (Windows Explorer) to view files created from process (.tif & .tfw). Close-up shows worldfile opened in Notepad.

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The final step is to clear the memory file before proceeding with processing your next raw ASTER data file. From the Available Bands list click on file, scroll to and click Close All Files. In the Warning dialog box Click Yes. The memory is now clear and ready for your next file.

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Opening Raster Images in ArcCatalog and ArcMap Note: Very Important: Use ArcCatalog as your browser to move or delete files to avoid corrupting your data files. Open ArcCatalog and navigate to your Processed data folder. Highlight your ASTER file (if opening image for the first time you will get the Generate pyramids dialog box). Click Yes to build pyramids.

View your file in the Preview window. Launch ArcMap using the Icon on the Toolbar.

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Open an empty ArcMap. Click OK Click on the Add Data Button

In the Add Data dialog box, navigate to your folder containing your file, click on file to be opened and click on the Add button.

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View of Image before symbology manipulation.

Right click on image layer to get to the Layer Properties dialog box. Click on the Source tab and scroll to the bottom to view information about Statistics. (This image can be taken into ERDAS to recalculate the statistics to get a sharper image).

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Layer Properties tabs views… General tab: Rename layer for Table of Contents (TOC) and specify scale range options.

Source tab: Contains Raster, Extent, Spatial Reference, and Statistics Information. The Set Data Source button is used for updating a link to a data source.

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Extent tab: Used for identifying the coordinates of the window in map space.

Display tab: Used for setting map tips, raster resolution, interactive display, resample during display, layer transparencies, and display quality.

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Symbology tab: ArcGIS Desktop Help has detailed descriptions about symbolizing raster images. (Key words for Index- symbolizing, images and other rasters in ArcMap)

The following settings were used for the image on our display. Channel bands were reordered, display background value was activated, and Stretch type was set for Standard Deviation.

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View of image after corrections.

Map Layout showing differences side by side.

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