Importing Satellite Data

There are two ways to import images into ERDAS Environment. If user already known that the image is IRS IC/ID Type, then import that image directly by selecting the Image type option as IRS 1C/1D (Super Structured Format). Otherwise, Select the Image type option as Generic Binary. With this Generic Binary option user can import any type of image. In this exercise we will import the images using the option Generic Binary

1. Click on IMPORT Icon on the Main Tool Bar. Then it will display the IMPORT/EXPORT Window as shown below

2. Since we are importing the Images into ERDAS Environment Keep the Default Option IMPORT
3. Click on the TYPE list option box. Then it will display all ERDAS supported file formats
4. Select GENERIC BINARY type as the option for Image Type
5. Similarly, select the Media as FILE
6. Select Input file i.e IMAGERY L-3. This is available in this path D:\ERDAS_Exercise_Files\trpc20026j099- 059\product1\imagery L-3
7. Browse for the OUTPUT Location as D:\ERDAS_Exercise_Files\
8. Type file name as IMAGE99-59

i. Data Formats For Digital Satellite Imagery

Digital data from the various satellite systems supplied to the user in the form of computer readable tapes or CD-ROM. As no worldwide standard for the storage and transfer of remotely sensed data has been agreed upon, though the CEOS (Committee on Earth Observation Satellites) format is becoming accepted as the standard. Digital remote sensing data are often organized using one of the three common formats used to organize image data . For an instance an image consisting of four spectral channels, which can be visualized as four superimposed images, with corresponding pixels in one band registering exactly to those in the other bands. These common formats are:

· Band Interleaved by Pixel (BIP)
· Band Interleaved by Line (BIL)
· Band Sequential (BSQ)

Digital image analysis is usually conducted using Raster data structures - each image is treated as an array of values. It offers advantages for manipulation of pixel values by image processing system, as it is easy to find and locate pixels and their values. Disadvantages becomes apparent when one needs to represent the array of pixels as discrete patches or regions, where as Vector data structures uses polygonal patches and their boundaries as fundamental units for analysis and manipulation. Where as vector format is not appropriate for digital analysis of remotely sensed data.

ii. Identifying Number of Rows, Columns and Bands for the Image

1. Then click on the DATA VIEW. The Data View Window is displayed as shown below. It contains the information about the image data, that is data about Number of Rows, Columns and Bands etc.

2. Here the numbers of rows are equal to sum of rows of each band, so the total number of rows for each band is equal to total number of rows/4. Note down the number of rows, columns and bands. The complete detail of the imagery is given in word document SURFUR.DOC in the Product1 folder

Total Number of Rows : 24020
Number of Rows : 6005
Number of Columns : 6480
Number of Bands : 4

Close the above window

3. Click on OK
4. The Import Generic Binary Data Window is displayed as shown below

5. Keep the DATA FORMAT as default option i.e is BIL
6. Type the FILE HEADER BYTES are 540
7. Type the Values for the Number of Rows i.e 6005, Number of Columns i.e 6480and Number of Bands i.e 4, for which you have already noted the values from the data View Window
8. Click on the PREVIEW Tab to preview the Image on the viewer. If the Preview is visible correctly, then close the preview window
9. Click on OK. Then it will display IMPORTING GENERIC BINARY DATA window.
10. Click on OK, if JOB STATE: DONE
11. Click on CLOSE to exit from import generic binary data window

iii. Open the Imported Imagery in the Viewer

1. Click on the VIEWER Icon on the Main Tool Bar
2. Select the CLASSIC VIEWER is the Viewer Type
3. Click on the File Menu of the Viewer Window
4. Click on OPEN
5. Select RASTER LAYER option
6. Then Browse for the File IMAGE99-59.IMG and select the same file
7. Click on OK to display on the viewer
8. Click on the RIGHT CLICK of the Mouse and Select FIT IMAGE TO WINDOW option to display the entire image on the screen. Now you can observe that RASTER Menu is added to the Viewer Menu Bar, since presently Raster image is displayed on the window
9. Now observe that, this raster image is not rectified image. When you place the cursor at any place on the image. Then it will display only the X, Y position of that location. Since it is not rectified you may not get results accurately
10. Close this Viewer