4. Level-1A Data Product 4.1. Outline of Contents Figure 4-1 shows an outline of Level-1A data products. Level-1A data are formally defined as reconstructed, unprocessed instrument data at full resolution. According to this definition the ASTER Level-1A data consists of the image data, the radiometric coefficients, the geometric coefficients and other auxiliary data, without applying the coefficients to the image data, thus maintaining the original data values. Scene cutting is applied to Level-0B data according to the predetermined World Reference System (WRS). Each group of data is divided into scenes every 60 km in the along-track direction. Each scene size is 63 km to include an overlap of 5 % with neighboring scenes except for band 3B. For band 3B the scene size is 81km, including an additional overlap of 6 km to compensate for the terrain error contribution and scene rotation for a large cross-track pointing (Figure 4-1). This scene cutting is necessary to granularize the Level-1A data products. It does not necessarily mean that the scene position is rigidly predetermined: it is still possible to revert to Level-0B data for a different cut of the scene. The Level-1A data product is an HDF file, which contains a complete set of image data for one scene, radiometric and geometric correction tables, and so on, as shown in Figure 4-1. Figure 4-1 Level-1A data product outline Table 4-1 shows the Level-1A data product size. Table 4-1 Level1A Data Product Size Item Data size (byte) Data Directory 8,192 Generic Header about 4,000 Specific Header about 10,100 Cloud Coverage Table 1,365 Ancillary Data about 1,728 Supplement Data about 1,379,550 VNIR Image Data 74,660,000 SWIR Image Data 25,804,800 TIR Image Data 4,900,000 Radiometric Correction Table 355,656 Geometric Correction Table 4,746.080 Total about 111 MB