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# How to convert ASTER L1A to L1B using ERDAS ER Mapper?

by ‎02-24-2016 12:12 PM - edited ‎03-23-2016 01:43 PM (692 Views)

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## Question

How to convert ASTER L1A to L1B using ERDAS ER Mapper?

ASTER L1A data are generally delivered in HDF format with an associated metadata file.

Import the ASTER L1A HDF data to ERS format using ER Mapper's HDF wizard, but do not include the 3B band. ASTER HDF image data includes three groups of bands: VNIR, SWIR and TIR, and these bands have 15 meter, 30 meter, and 90 meter pixels sizes respectively. Import each group separately. They can be merged together later by using the ASTER Wizard in ER Mapper. The bands to import are 1-3 for VNIR, 5-10 for SWIR and 11-15 for TIR.

When the import is finished go to the ER Mapper main menu > Process > Geocoding Wizard. Select one of the files you just created as the input file and select Polynomial, then move on to step 2. Choose linear and advance to step 3. Choose projection and coordinate type info and go to step 4. Open the ASTER metadata file in WordPad and search for "GRing". It will show you the Lat/Long information for the four corners of the data. It should appear similar to the example below:

GROUP = GRingPoint
CLASS = "1"
OBJECT = GRingPointLatitude
CLASS = "1"
Value = (22.8268, 22.7424, 22.1854, 22.2695)
TYPE = "DOUBLE"
NUM_VAL = 4
END_OBJECT = GRingPointLatitude
OBJECT = GRingPointLongitude
CLASS = "1"
Value = (88.1100, 88.7057, 88.5745, 87.9811)
TYPE = "DOUBLE"
NUM_VAL = 4
END_OBJECT = GRingPointLongitude

OBJECT = GRingPointSequenceNo
CLASS = "1"
Value = (1, 2, 3, 4)
TYPE = "INTEGER"
NUM_VAL = 4

Add ground control points from the metadata file in the Geocoding wizard.

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