|Introduction | Sustainability Factors | Content Categories | Format Descriptions | Contact|
|Full name||Band Sequential (BSQ) Image File|
A binary raster file format for aerial photography, satellite imagery, and spectral data. The BSQ data organization can handle any number of bands, and thus accommodates black and white, grayscale, pseudocolor, true color, and multi-spectral image data. Additional information is needed to interpret the image data, such as the numbers of rows, columns, and bands, if there is a color map, and latitude and longitude to relate the image to geospatial locations. This information may be supplied in a file header (typical on the legacy tapes originally used for storing satellite image data) or in a companion file, for example, as an ASCII header (.hdr) file in the ESRI implementation (See Notes). A BSQ image file is generally one member of a pair or cluster of companion files that are typically stored in the same file directory or project workspace, with all component files having the same filename and identified by individual file extension. Images stored in BIP format have values for all pixels for the first band, followed by the data for the second band, etc. This format is optimal for spatial (X, Y) access to any part of a single spectral band. See BSQ_enc for more specific encoding information.
|Production phase||Raster image file produced, for example, by remote sensing systems.|
|Relationship to other formats|
|Contains||BSQ_enc, Band Sequential Image Encoding|
|May have component||ESRI_World, ESRI World File. To relate pixel dimensions to real-world coordinates.|
|LC experience or existing holdings|
|Disclosure||Documentation is provided by multiple sources, including the publicly available specification from Environmental Systems Research Institute, Inc. (ESRI).|
|Documentation||Extendable Image Formats for ArcView GIS 3.1 and 3.2; ESRI White Paper, July 1999; Description of BIL/BIP/BSQ is on page 8.|
|Adoption||A common raster file format and remote sensing data standard. Landsat Thematic Mapper sensors have used BSQ as a primary format. BSQ format is supported in many GIS, image processing, remote sensing analysis and spatial modeling applications, including: ESRI products, ERDAS ER Mapper & ERDAS IMAGINE, Envi and IDRISI.|
|Licensing and patents||None.|
|Transparency||The raw data has a simple form and is easily interpreted if the image dimensions in pixels, the number and characteristics of spectral bands, and the number of bits per band are known.|
|Self-documentation||An embedded or companion ASCII header file may contain a wide range of data regarding image capture instrumentation, date, and other data for identifying, displaying, and georeferencing the image.|
|External dependencies||Accompanying header files may be compatible only with certain software applications.|
|Technical protection considerations||No capabilities for encryption or other technical protection mechanism inherent in the format or in its use have been found by the compilers of this analysis.|
|Normal rendering||See BSQ_enc.|
|Clarity (high image resolution)||See BSQ_enc.|
|Color maintenance||See BSQ_enc.|
|Support for vector graphics, including graphic effects and typography||See BSQ_enc.|
|Support for multispectral bands||The BSQ data organization can handle any number of bands, and thus accommodates black and white, grayscale, pseudocolor, true color, and multi-spectral image data. BSQ data can store pixel information for separate bands within the same file; the organization stores all data for each band in a single bitstream. As opposed to formats such as a multi-band GeoTIFF (where all the bands are in one file), BSQ data sets give the user the option of convenient downloading of only relevant bands.|
|Functionality beyond normal rendering||When supported by suitable georeferencing information and metadata to support interpretation of spectra in accompanying files, as is often the case in practice for geospatial data, this file format supports geospatial analysis, including grid-based analysis.|
|GIS images and datasets|
|Normal functionality||BSQ files are often produced by remote sensing systems. BSQ data can be immediately read/accessed with ESRI and other GIS applications, including USGS Digital Data Viewer. This format is optimal for spatial (X, Y) access of any part of a single spectral band.|
|Support for GIS metadata||In ESRI's BSQ implementation, accompanying files provide ancillary information, including metadata. In particular, projection information is provided in an ASCII text file with extension .prj. The ESRI world file, with extension .bqw, is an ASCII text file containing coordinate information. It is used by some packages for geo-referencing of BSQ image data. The ESRI header file, with extension .hdr, can contain a wide range of data regarding image capture instrumentation, date, and other data for identifying, displaying, and georeferencing the image.|
|Support for grids||As a raster format, data in the BSQ encoding is inherently adaptable to grid-based analysis, so long as accompanying information is provided to document the scale, coordinate reference system, and projection so that the image can be registered against a grid chosen for analysis. An ESRI BSQ file (with its supporting files) is easily converted to the ESRI Grid format.|
BSQ, BIL, and BIP represent alternative ways of storing images in memory or on disk. The initials stand for band-sequential, band-interleaved-by-line, and band-interleaved-by-pixel, respectively. These image formats are also sometimes called "band-interleaved", "row-interleaved", and "pixel-interleaved", respectively. Images are stored in one format or another to facilitate expected image manipulations. The BSQ (band-sequential) encoding is optimal for spatial (x,y) access within a single band.
To be interpreted properly, a BSQ binary image file must have an associated ASCII header file. This header file contains ancillary data about the image such as the number of rows and columns in the image, if there is a color map, and latitude and longitude.
In ESRI applications, accompanying the BSQ file are four image description files (each in ASCII text format): a header file, a statistics file, a resolution file, and a color file. The header file (.hdr) describes the nature of the image data, through the use of keywords and values. The statistics file (.stx) is an optional file that describes the image statistics for each spectral band. It records the minimum and maximum pixel values, the mean, the standard deviation, and the two linear contrast stretch parameters. The resolution file (.bqw), also known as a "world file" describes the height and width of each cell and the coordinate position of the top left cell of the data. The color file (.clr) is an optional file that describes the image colormap.