Overview
The BIL, BIP and BSQ raster data formats were originally developed by USGS for CCT tape formats for Landsat satellite data from 1972 on. These are simple uncompressed binary files representing a raster of one or more image bands, accompanied by an ASCII header file (*.hdr) with image information. The main file extension depends on the format, or storage sequence:
*.BIL : Bands Interleaved by Pixel
*.BIP : Bands Interleved by Line
*.BSQ : Bands Sequential
File Format
The file format was documented by ESRI online. (PDF version) and supports integer (8,16 or 32 bit) pixel values in signed or unsigned format, in either little- or big endian storage order. The 1- and 4- bit integer pixel formats have not been implemented (yet) as they seem less useful for FEWS, but the rest of the documentation is fully implemented.
BIL files in FEWS
In the Public Interface (PI interface) of FEWS, an implementation of the BIL format is also provided, as documented here.
The PI implementation of BIL files however includes several adaptations to specific FEWS purposes (i.e. using floating point data, extension for time series using blocks) which causes this FEWS implementation to not fully comply with the official specifications of the BIL format and changing this structure would break backward compatibility so it was decided to create a new parser, which als properly supports the BIL, BIP and BSQ format.
This new implementation is fully compliant with the ESRI technical specifications, but does NOT offer specific FEWS extensions to the format for dealing with time series or floating point pixel values, this new importer can be configured with the new "BILBIPBSQ" identifier, whereas the existing PI implementation of FEWS BIL files uses the identifier "BIL".
Configuration
The following configuration example shows what is required to import BIL/BIP/BSQ format satellite data into FEWS. The following files need to be adjusted:
- Locations.xml: to add the satellite location ID
- Grids.xml: for the grid characteristics
- Import_BIL.xml: module instance that imports the data (for example)
- IDMapping file if a special parameter ID needs to be specified
- ModuleInstanceDescriptors.xml: For reference of the import module instance
- ImportUnitConversions.xml: If the units need to be converted on importing
For some of these files examples are provided below. Locations, ModuleInstanceDescriptors and ImportUnitConversions are standard FEWS configuration files.
Example of the locations.xml file element:
Example of the Grids.xml file element:
An example import Module instance configuration file to import a BSQ file containing 2 parameters (bands):
