Canadian Space Agency

Centre for Research in Earth and Space Technology

The Institute for Space and Terrestrial Science

Thomson-csf Optronics Canada Inc.

Allan B Hollinger

Shen-En Qian

Charles H Hersom

Zvika Afik

Luc Gagnon

Paul J Thomas

Daniel J Williams

Shen-en Qian

The present invention relates to a real-time wideband compressor for multi-dimensional data. The compressor comprises a plurality of compression engines for simultaneously compressing a plurality of data subsets of a set of input data vectors and providing compressed data thereof using one of SAMVQ or HSOCVQ data compression. Each compression engine comprises an along spectral vectors codevector trainer as well as an across spectral bands codevector trainer. The compression engines are programmable to perform either along spectral vectors codevector training or across spectral bands codevector training in combination with one of the SAMVQ or HSOCVQ techniques without changing hardware. The compressor further comprises a network switch for partitioning the set of input data vectors into the plurality of data subsets, for providing each of the plurality of data subsets to one of the plurality of compression engines, and for transmitting the compressed data. The real-time wideband compressor is highly advantageous in, for example, space applications by programmable enabling performance of different techniques of codevector training as well as different techniques of VQ. Furthermore, after the compression process is started the compression process is performed autonomously without external communication.

Codevector trainers and real-time compressor for multi-dimensional data

Methods and systems for compressing a continuous data flow for numerous applications where it is necessary to process large data sets such as hyper-spectral data cubes in real-time. A predetermined number of 2D focal plane frames in a boundary area of a previous regional data cube close to a current regional data cube are included in a training set used for codevector training for the current region. Therefore, no artificial boundary occurs between the two adjacent regions when codevectors trained in this way are used for codebook generation and encoding of the spectral vectors of the current regional data cube. This process substantially reduces image artifacts between adjacent regions. A remedy for the single bit error problem is also provided. Full redundancy of compressed data for a regional data cube is obtained by combining a previous regional data cube and the current regional data cube for codebook training. In order to obtain redundancy for the index map, the codebook is used to encode the current regional data cube as well as the previous regional data cube producing a baseline index map for the current regional data cube and a redundant index map for the previous regional data cube. Therefore, full redundancy for a regional data cube is provided allowing restoration of a regional data cube even if its codebook and/or index map are corrupted or lost due to single bit errors.

Method of coding a continuous data flow using vector quantization

The present invention relates to a method and system for compressing a continuous data flow in real-time based on lossy compression. In real-time data compression, a series of multi-dimensional data subsets acquired in a given period of time are treated as a regional data cube for the purpose of dividing a continuous series of data subsets into a plurality of data cubes. In a first embodiment implementation of parallel processing using a plurality of compression engines is facilitated by separating a data cube into a plurality of clusters comprising similar spectral vectors. By separating the data cube into clusters of similar spectral vectors no artificial spatial boundaries are introduced substantially improving image quality. Furthermore, the spectral vectors within a cluster are more easily compressed due to their similarity. In a second embodiment a predetermined number of 2D focal plane frames in a boundary area of a previous regional data cube close to a current regional data cube are included in a training set used for codevector training for the current region. Therefore, no artificial boundary occurs between the two adjacent regions when codevectors trained in this way are used for codebook generation and encoding of the spectral vectors of the current regional data cube substantially reducing image artifacts between adjacent regions. A remedy for the single bit error problem is provided in a third embodiment. Full redundancy of compressed data for a regional data cube is obtained by combining the previous regional data cube and the current regional data cube for codebook training. In order to obtain redundancy for the index map, the codebook is used to encode the current regional data cube as well as the previous regional data cube producing a baseline index map for the current regional data cube and a redundant index map for the previous regional data cube. Therefore, full redundancy for a regional data cube is provided allowing restoration of a regional data cube if its codebook and/or index map are corrupted or lost due to single bit errors.

Method and system for compressing a continuous data flow in real-time using cluster successive approximation multi-stage vector quantization (SAMVQ)

Data compression engines and real-time wideband compressor for multi-dimensional data

The present invention relates to a method for compressing a continuous data flow based on lossy compression. In real-time data compression, a series of data subsets acquired in a given period of time are treated as a regional data cube for the purpose of dividing a continuous series of data subsets into a plurality of data cubes. Reuse of existing codevectors is important in achieving high compression performance. For encoding spectral vectors on a subset-by-subset basis in a current region two types of codevectors are used, codevectors that have been newly trained for previous data subsets in the current region and codevectors trained for the previous region. The problem of a visible spatial boundary between two adjacent regions after decompression is overcome by reusing the codevectors trained from a previous region to encode the spectral vectors in the current region in order to attain a seamless conjunction of the two adjacent regions. Experimental results show that the method for compressing a continuous data flow in real-time according to the present invention performs as well as data compression performed in batch mode. Therefore, the method is highly advantageous in, for example, space applications or medical imaging.

Method and system for compressing a continuous data flow in real-time using recursive hierarchical self-organizing cluster vector quantization (HSOCVQ)

The present invention relates to a method of encoding a hyper-spectral image datacube using vector quantization. According to the invention, a temporary codebook having a small number, n, of codevectors is generated from the datacube. The datacube is processed using the temporary codebook to form n clusters (subsets) of vectors. A codevector corresponds to a cluster and is the centre of gravity for the cluster. In the compression process, vectors in each cluster are encoded by the corresponding codevector. Then the reconstruction fidelity of the encoded cluster is evaluated. When the fidelity of an encoded cluster is better than a predetermined fidelity, the codevector relating to that cluster is stored in a final codebook and the vectors in the cluster are expressed with the index (address) of the codevector in the final codebook. When the fidelity of an encoded cluster is not suitable, the cluster is reencoded with a new temporary codebook generated from this cluster, and the same process is repeated. The compression process is recursively implemented until all clusters are processed.

System and method for encoding multidimensional data using hierarchical self-organizing cluster vector quantization

The present method relates to a method for encoding image data using vector quantization. According to the invention, a small first codebook is determined. Each image vector of the image data is then encoded by determining a codevector within the first codebook that best approximates the image vector within the image data. A first index map is generated by replacing each image vector with an index indicative of the codevector's location within the first codebook. Then difference data are evaluated based on the original image data and the encoded image data. Each error vector of the difference data is then encoded using another small codebook. In another index map the error vectors are then replaced with an index indicative of the codevector's location within the other codebook. Evaluation of the error based on the difference data and the encoded difference data provides new difference data which is used to evaluate the fidelity of the approximation process performed for compression. The steps of encoding of the difference data are repeated until a control error of the difference data is smaller than a given threshold.

System and method for encoding/decoding multidimensional data using successive approximation multi-stage vector quantization

The present invention relates to a method of viewing and processing hyper-spectral image data compressed using a VQ algorithm. According to the invention the data is compressed using a codebook of codevectors including binary spectral vectors, which allows processing of the compressed data and viewing of data within a datacube without expanding the compressed data into the complete datacube. In order to view an image derived from a datacube, for each pixel within the image a location within the datacube is selected, an index value from the index map at that location is retrieved, and a spectral value from a spectral vector within the codebook is retrieved for said pixel, the spectral vector identified by the retrieved index. A single spectral vector is easily viewed by displaying a spectral vector from the codebook.

System for interactive visualization and analysis of imaging spectrometry datasets over a wide-area network

The present invention provides a method for distinguishing a boundary of an object, and the object itself, from its background. In the method electromagnetic radiation is detected from at least one field of view substantially spanning the boundary of the object and background adjacent to the boundary and superimposed or overlaid as images onto a detector. The method includes correlating spatial transitions in intensity of the overlaid images on the detector with a boundary of the object. When used for determining the attitude of a satellite with respect to the earth, the detector is a thermal infrared detector thereby providing a sharp contrast between the thermal emission of the earth and cold space. The invention provides a simple, effective method and device for determining satellite orientation and/or attitude with respect to a thermal infrared-emitting target body. The sensor includes a segmented limb-looking mirror to provide multiple fields-of-view within the field-of-regard and superimposing these fields-of-view as images onto a common detector. The required resolution can be obtained while providing a wide range of operational orbital altitudes. The attitude of the satellite can vary by a large angle from the minimal orientation while still permitting an accurate determination of attitude. Multiple channels in a modular form provide redundancy, improved accuracy, and the opportunity of providing more diverse configurations. The utilization of uncooled microbolometer arrays as imaging detectors removes the requirement for additional cooling equipment thereby providing a low cost, small size and low mass sensor with configurational flexibility and no moving parts.

Satellite attitude sensor using thermal imaging

The present invention provides a method for distinguishing a boundary of an object, and the object itself, from its background. In the method electromagnetic radiation is detected from at least two fields of view substantially spanning the boundary of the object and background adjacent to the boundary and superimposed or overlaid as images onto a detector. The method includes correlating spatial transitions in intensity of the overlaid images on the detector with a boundary of the object. When used for determining the attitude of a satellite with respect to the earth, the detector is a thermal infrared detector thereby providing a sharp contrast between the thermal emission of the earth and cold space. The invention provides a simple, effective method and device for determining satellite orientation and/or attitude with respect to a thermal infrared-emitting target body. The sensor includes a segmented limb-looking mirror to provide multiple fields-of-view within the field-of-regard and superimposing these fields-of-view as images onto a common detector. The required resolution can be obtained while providing a wide range of operational orbital altitudes. Multiple channels in a modular form provide redundancy, improved accuracy, and the opportunity of providing more diverse configurations. The utilization of uncooled microbolometer arrays as imaging detectors removes the requirement for additional cooling equipment thereby providing a low cost, small size and low mass sensor with configurational flexibility.

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Toronto, Canada

Allan B Hollinger