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Radar, Sonar and Navigation, IEE Proceedings -

Issue 3 • Date Jun 1997

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Displaying Results 1 - 9 of 9
  • Compression of SAR images using KLT, VQ and mixture of principal components

    Publication Year: 1997 , Page(s): 113 - 120
    Cited by:  Papers (3)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1880 KB)  

    Owing to the very high-resolution nature of synthetic aperture radar (SAR), any use of image compression on such data must minimise the degree of distortion introduced. Two common methods for compressing images are linear block transform coding, such as the Karhunen-Loeve transform, and vector quantisation. However, the implicit assumption of stationarity for these techniques is far from valid for most images. As a result, they introduce distortions in regions within an image that are significantly different from its global statistics. A new approach to data representation, referred to as the mixture of principal components (MPG), is proposed which combines advantages of both transform coding and vector quantisation. Like vector quantisation, it partitions the input space into a number of non-overlapping regions, and each region is represented by a number of basis vectors in the manner of transform coding. When applied to the compression of SAR images, the MPC method introduces less distortion for a given compression ratio compared with the other two techniques. For example, at 0.25 bits per pixel (a compression ratio of 64:1). The degree of distortion is reduced by close to 3 dB. When the resulting images are compared, the visibility of the distortion is also reduced when the new method is used View full abstract»

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  • High resolution sea clutter data: statistical analysis of recorded live data

    Publication Year: 1997 , Page(s): 121 - 130
    Cited by:  Papers (64)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (896 KB)  

    The paper is devoted to a detailed analysis of experimental data, collected at Osborne Head Gunnery Range with McMaster University IPIX radar, to test theoretical models developed in the literature. The validity of the compound model has been proven for VV polarisation both for amplitude and correlation properties. Cross-polarised data also exhibit a compound behaviour but require an additional Gaussian component due to thermal noise. HH data deviate from the K model and seem to better approach a log-normal distribution. Previous results have been obtained by a correlation test that allows separation of the short and long correlation terms, a modified Kolmogoroff Smirnoff test to verify the fitting and a cumulants domain analysis to quantify the Gaussian component. The interest of the work lies in its application for successful radar design View full abstract»

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  • Adaptive decision fusion for unequiprobable sources

    Publication Year: 1997 , Page(s): 105 - 111
    Cited by:  Papers (21)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (528 KB)  

    An optimal decision rule has been derived by Chair and Varshney (1986) for fusing decisions based on the Bayesian criterion. However, to implement such a rule, the miss probability PM and the probability of false alarm PF for each local detector must be known, and these are not readily available in practice. To circumvent this situation, an adaptive fusion system for equiprobable sources has been developed. The system is extended to unequiprobable sources; thus its practicality is enhanced. An adaptive fusion model using the fusion result as a supervisor to estimate the PM and PF is introduced. The fusion results are classified as `reliable' and `unreliable'. Reliable results are used as a reference to update the weights in the fusion centre. Unreliable results are discarded. The convergence and error analysis of the system are demonstrated theoretically and by simulations. The paper concludes with simulation results that conform to the analysis View full abstract»

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  • Robust monoparametric multiradar CFAR detection against non-Gaussian spiky clutter

    Publication Year: 1997 , Page(s): 131 - 140
    Cited by:  Papers (2)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1140 KB)  

    The problem of decentralised constant false alarm rate (CFAR) detection in a distributed multiradar system is considered. First, the way in which an incorrect assumption of the clutter model affects the false alarm rate (FAR) of state-of-the-art decentralised multiradar systems is investigated, revealing current flaws of distributed detection techniques developed under the Gaussian assumption. Results show that the FAR of current distributed architectures degrades intolerably when non-Gaussian spiky clutter is present. On the other hand, state-of-the-art biparametric CFAR algorithms for non-Gaussian clutter are computationally demanding and lossy, so the question that arises is: are they really necessary? It is shown that the answer is `no', or rather, `not always'. A new distributed detection strategy with simple monoparametric multipulse CFAR detectors is proposed, that, in spite of the single parameter estimation, allows one to obtain a false alarm probability at the fusion centre robust against changes of the degree of clutter spikiness. The robustness is obtained by the joint action of multisensorial integration and local temporal integration, in conjunction with a specific choice of the local monoparametric estimator. After a robustness analysis of the algorithm the detection performance of the multiradar network is determined and a comparison with a decentralised system employing biparametric estimation algorithms presented View full abstract»

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  • Effect of skywave interference on coverage of radiobeacon DGPS stations

    Publication Year: 1997 , Page(s): 163 - 168
    Cited by:  Patents (27)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (668 KB)  

    Coastal radiobeacon stations, which have long served marine direction-finding receivers, are increasingly being employed to transmit differential satellite navigation system (DSNS) correction messages to marine users. The range of these 300 kHz data transmissions extends beyond the nominal ranges of the radiobeacons into regions where skywave effects become significant, especially at night. The paper demonstrates by statistical analysis and experimental measurements that skywave-propagated components interact with the wanted groundwaves, causing deep signal fading that can lead to loss of data. Also, in Europe, skywave signals from other radiobeacons on the same, or adjacent, channels cause severe interference. A coverage and performance prediction model that takes these effects into account, together with atmospheric noise and attenuation due to ground losses, is used to illustrate the reduction of usable range caused by skywave propagation. The paper argues that it is essential to allow for skywave factors when predicting the operating areas of beacons and when allocating frequencies within the radiobeacon DSNS service View full abstract»

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  • (Editorial) Advances In Navigation

    Publication Year: 1997 , Page(s): 141 - 142
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (200 KB)  

    First Page of the Article
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  • Global navigation satellite system in an integrated air traffic management constellation

    Publication Year: 1997 , Page(s): 156 - 162
    Cited by:  Papers (1)  |  Patents (4)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (708 KB)  

    Enhanced surveillance, communications and navigation are the primary functions needed for an advanced air traffic management (ATM). To provide ATM globally, including areas not covered by terrestrial systems, the advantages of satellite technology must be exploited. In a previous work, a novel architecture based on low-elevation elevation orbit satellites was described and evaluated. The satellite constellation is designed to supply the surveillance and data link capabilities equivalent to an advanced secondary surveillance radar mode S, as well as to provide satellite communication and navigation functions. Such a co-operative independent surveillance integrating navigation and communication (CISINC) is fully compliant with the communication, navigation and surveillance/air traffic management concept endorsed by the ICAO in 1991. The space-based implementation of CISINC is called ATM-Star. The paper treats the navigation component of ATM-Star called GNSS-LEO, which is compatible with today's GPS receivers and aims to be a solution for the global navigation satellite system phase 2 View full abstract»

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  • Efficient technique to fix GPS carrier phase integer ambiguity on-the-fly

    Publication Year: 1997 , Page(s): 148 - 155
    Cited by:  Papers (6)  |  Patents (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (660 KB)  

    A new and fast method to fix integer ambiguity of GPS carrier phase measurement on-the-fly is proposed. The method is distinguished from other methods in that the relationship between integer ambiguities is found and used in a constraint equation for fixing integer ambiguity. Thus the method does not require positioning for every candidate and only three independent elements of the integer ambiguities are searched: the remaining dependent elements can be obtained from the constraint equation. This may greatly reduce the computational burden. Accurate relative positioning on the move also can be accomplished by adopting the proposed method. The technique is applied to two different types of real data to show its effectiveness. Experimental results show that the proposed method is fast and efficient for relative positioning of a moving user. The method may be used in areas requiring accurate positioning such as navigation and geodesy View full abstract»

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  • Digital charting: a Royal Navy navigator's view

    Publication Year: 1997 , Page(s): 143 - 147
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (612 KB)  

    The IMO have given their approval to the concept of an electronic chart display and information system (ECDIS) (IMO Assembly resolution A.817(19)) but the detailed technical specification required for Type Approval is still to be completed. Meanwhile, the approved `vector data' required for ECDIS is only just beginning to be available and its form is still evolving. The Royal Navy is moving towards adoption of this new technology and has mandated its use for a future class of frigate. It is already involved in trials of prototype equipment, albeit using a (raster) data format which has yet to receive international approval. Trials supported by UK manufacturers and the UK Hydrographic Office are proving beneficial to all involved and vector data was incorporated during 1996. The need to strike a balance between adapting current navigation techniques to the electronic era and devising new ones has already been recognised, as is the inevitable impact on training. The ability to measure positions, bearings and distances far more accurately than ever before is putting the hydrographers on their mettle, while the need to understand and correctly apply datum shifts and match projections when displaying different forms of data is posing a new challenge for the navigator. The end of the paper chart in the RN may be forecastable but is not yet in sight and there are a number of questions that need to be resolved before ECDIS becomes accepted as the prime method of navigation View full abstract»

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Aims & Scope

IEE Proceedings Radar, Sonar and Navigation covers the theory and practice of systems involving the processing of signals for radar, radio location, radio navigation and surveillance purposes.

Full Aims & Scope