The HDF4 ASTER Reader module provides FME with access to continuous numeric or classified color data in multiple bands.
Overview
HDF stands for Hierarchical Data Format, and is a container for several different datasets, including one or more raster images. It is used most often for storing Scientific Datasets (SDS), which are multidimensional arrays filled with data. One HDF file may contain several different SDS arrays. They may differ in size, number of dimensions and may represent data for different regions.
The HDF4 ASTER reader can read both HDF4 and HDF4-EOS files. The latter is a modification of HDF maintained by NASA’s EOS (Earth Observing System). HDF4-EOS is used for storing telemetry from NASA’s ‘Terra’ and ‘Aqua’ satellites. HDF5-EOS is used for storing telemetry from ‘Aura’ satellites.
Since HDF is a container for datasets rather than a dataset itself, it can contain various subdatasets, which are in most cases associated with a particular imaging sensor. ASTER data is produced in several levels representing the amount of processing that has been done. Level 1A is raw image data, level 1B is image data with radiometric and geometric coefficients applied, and level 2 is higher-level data processed to ‘stretch’, or enhance the color in the image.
This reader supports ASTER HDF level 1A, level 1B and level 2 as well as ASTER HDF-EOS data. ASTER raster images always contain 15 bands collected from VNIR, SWIR and TIR sensors, with each band represented as a separate subdataset in FME and are by default processed as swaths.
GCPs (ground control points) present along with a projection in an ASTER file being read can either be applied to the data as an affine transformation, or stored as properties of the raster geometry.
Reader Overview
The FME considers a top-level ASTER container file to be a dataset.
FME Raster Features
FME raster features represent raster data and use several concepts that are unlike those used in the handling of vector data.
For comprehensive information about how FME processes raster data, see Rasters.