Band interleaved by line (BIL) is one of three primary methods for encoding image data for multiband raster images in the geospatial domain, such as images obtained from satellites. This simple uncompressed raster data encoding is easily and frequently described, requiring no formal specification. BIL is not in itself an image format, but is a scheme for storing the actual pixel values of an image in a file band by band for each line, or row, of the image. The raw data has a simple form and is easily interpreted if the image dimensions in pixels, the number of spectral bands, and the number of bits per band are known. For example, given a three-band image, all three bands of data are written for row one, all three bands of data are written for row two, and so on. The BIL encoding is a compromise format, allowing fairly easy access to both spatial and spectral information. The BIL data organization can handle any number of bands, and thus accommodates black and white, grayscale, pseudocolour, true colour, and multi-spectral image data.
Additional information is needed to interpret the image data, such as the numbers of rows, columns, and bands, and relate the image to geospatial locations. This information may be supplied in a file header (typical on the tapes originally used for satellite image data) or in files associated with a raw image data file.
Spatial resolution and bit-depth are not limited by the BIL encoding per se but may be constrained in some usage contexts. There is no support for colour management in the BIL encoding. Documentation of spectral values for bands, or interpretation of false colours should be supplied in an accompanying data structure.
Band interleaved by pixel (BIP) is one of three primary methods for encoding image data for multiband raster images in the geospatial domain, such as images obtained from satellites. This simple uncompressed raster data encoding is easily and frequently described, requiring no formal specification. BIP is not in itself an image format, but is a method for encoding the actual pixel values of an image in a file. The raw data has a simple form and is easily interpreted if the image dimensions in pixels, the number of spectral bands, and the number of bits per band are known. Images stored in BIP format have the first pixel for all bands in sequential order, followed by the second pixel for all bands, followed by the third pixel for all bands, etc., interleaved up to the number of pixels. The BIP data organization can handle any number of bands, and thus accommodates black and white, grayscale, pseudocolour, true colour, and multi-spectral image data.
BIP data stores pixel information for separate bands within the same file, so that the user can choose to display just one specific band in a multi-band image. Therefore, BIP encoding provides optimal processing performance for spectral analysis (as compared with BIL or BSQ raster organization) as it supports efficient extraction of individual spectra and spectral averages.
Additional information is needed to interpret the image data, such as the numbers of rows, columns, and bands, and relate the image to geospatial locations. This information may be supplied in a file header (typical on the tapes originally used for satellite image data) or in files associated with a raw image data file.
Spatial resolution and bit-depth are not limited by the BIP encoding per se but may be constrained in some usage contexts. There is no support for colour management in the BIP encoding. Documentation of spectral values for bands, or interpretation of false colours should be supplied in an accompanying data structure.
Band sequential (BSQ) is one of three primary methods for encoding image data for multiband raster images in the geospatial domain, such as images obtained from satellites. This simple uncompressed raster data encoding is easily and frequently described, requiring no formal specification. BSQ is not in itself an image format, but is a method for encoding the actual pixel values of an image in a file. BSQ format is a very simple format, where each line of the data is followed immediately by the next line in the same spectral band. The raw data has a simple form and is easily interpreted if the image dimensions in pixels, the number of spectral bands, and the number of bits per band are known. This format is optimal for spatial (x, y) access of any part of a single spectral band. The BSQ data organization can handle any number of bands, and thus accommodates black and white, grayscale, pseudocolour, true colour, and multi-spectral image data.
A single band covering the entire scene is stored as a single bitstream making this encoding method convenient when only selected bands are needed. Each image band can be conveniently written to an independent file. BSQ can therefore be a preferable format for some forms of analysis as an application does not have to read past ancillary data in an image stack. As opposed to formats where the bands are interleaved (such as a multi-band GeoTIFF), BSQ data sets support convenient extraction of relevant bands. Some BSQ datasets are distributed as separate image files for each band, with common geospatial registration and a shared set of header information.
Additional information is needed to interpret the image data, such as the numbers of rows, columns, and bands, and relate the image to geospatial locations. This information may be supplied in a file header (typical on the tapes originally used for satellite image data) or in files associated with a raw image data file.
Spatial resolution and bit-depth are not limited by the BSQ encoding per se but may be constrained in some usage contexts. There is no support for colour management in the encoding. Documentation of spectral values for bands, or interpretation of false colours should be supplied in an accompanying data structure.