| 1. |
- Horney, Tobias, et al.
(författare)
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An information system for target recognition
- 2004
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Ingår i: Volume 5434 Multisensor, Multisource Information Fusion: Architectures, Algorithms, and Applications. - : SPIE - International Society for Optical Engineering. ; , s. 163-175
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Konferensbidrag (refereegranskat)abstract
- We present an approach to a general decision support system. The aim is to cover the complete process for automatic target recognition, from sensor data to the user interface. The approach is based on a query-based information system, and include tasks like feature extraction from sensor data, data association, data fusion and situation analysis. Currently, we are working with data from laser radar, infrared cameras, and visual cameras, studying target recognition from cooperating sensors on one or several platforms. The sensors are typically airborne and at low altitude. The processing of sensor data is performed in two steps. First, several attributes are estimated from the (unknown but detected) target. The attributes include orientation, size, speed, temperature etc. These estimates are used to select the models of interest in the matching step, where the target is matched with a number of target models, returning a likelihood value for each model. Several methods and sensor data types are used in both steps. The user communicates with the system via a visual user interface, where, for instance, the user can mark an area on a map and ask for hostile vehicles in the chosen area. The user input is converted to a query in ΣQL, a query language developed for this type of applications, and an ontological system decides which algorithms should be invoked and which sensor data should be used. The output from the sensors is fused by a fusion module and answers are given back to the user. The user does not need to have any detailed technical knowledge about the sensors (or which sensors that are available), and new sensors and algorithms can easily be plugged into the system.
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| 2. |
- Ulvklo, Morgan, et al.
(författare)
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A sensor management framework for autonomous UAV surveillance
- 2005
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Ingår i: Proceedings of SPIE 5787, Airborne Intelligence, Surveillance, Reconnaissance (ISR) Systems and Applications II. - : SPIE - International Society for Optical Engineering. ; , s. 48-61
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Konferensbidrag (refereegranskat)abstract
- This paper presents components of a sensor management architecture for autonomous UAV systems equipped with IR and video sensors, focusing on two main areas. Firstly, a framework inspired by optimal control and information theory is presented for concurrent path and sensor planning. Secondly, a method for visual landmark selection and recognition is presented. The latter is intended to be used within a SLAM (Simultaneous Localization and Mapping) architecture for visual navigation. Results are presented on both simulated and real sensor data, the latter from the MASP system (Modular Airborne Sensor Platform), an in-house developed UAV surrogate system containing a gimballed IR camera, a video sensor, and an integrated high performance navigation system.
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| 3. |
- Ahlberg, Jörgen, 1971-, et al.
(författare)
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An information measure of sensor performance and its relation to the ROC curve
- 2010
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Ingår i: Proc. SPIE 7695, Algorithms and Technologies for Multispectral, Hyperspectral, and Ultraspectral Imagery XVI. - : SPIE - International Society for Optical Engineering. ; , s. Art.nr. 7695-72-
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Konferensbidrag (refereegranskat)abstract
- The ROC curve is the most frequently used performance measure for detection methods and the underlying sensor configuration. Common problems are that the ROC curve does not present a single number that can be compared to other systems and that no discrimination between sensor performance and algorithm performance is done. To address the first problem, a number of measures are used in practice, like detection rate at a specific false alarm rate, or area-under-curve. For the second problem, we proposed in a previous paper1 an information theoretic method for measuring sensor performance. We now relate the method to the ROC curve, show that it is equivalent to selecting a certain point on the ROC curve, and that this point is easily determined. Our scope is hyperspectral data, studying discrimination between single pixels.
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| 4. |
- Ahlberg, Jörgen, 1971-, et al.
(författare)
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An information-theoretic approach to band selection
- 2005
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Ingår i: Proc. SPIE 5811, Targets and Backgrounds XI: Characterization and Representation. - : SPIE - International Society for Optical Engineering. ; , s. 15-23
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Konferensbidrag (refereegranskat)abstract
- When we digitize data from a hyperspectral imager, we do so in three dimensions; the radiometric dimension, the spectral dimension, and the spatial dimension(s). The output can be regarded as a random variable taking values from a discrete alphabet, thus allowing simple estimation of the variable’s entropy, i.e., its information content. By modeling the target/background state as a binary random variable and the corresponding measured spectra as a function thereof, wecan compute theinformation capacity ofa certainsensoror sensor configuration. This can be used as a measure of the separability of the two classes, and also gives a bound on the sensor’s performance. Changing the parameters of the digitizing process, bascially how many bits and bands to spend, will affect the information capacity, and we can thus try to find parameters where as few bits/bands as possible gives us as good class separability as possible. The parameters to be optimized in this way (and with respect to the chosen target and background) are spatial, radiometric and spectral resolution, i.e., which spectral bands to use and how to quantize them. In this paper, we focus on the band selection problem, describe an initial approach, and show early results of target/background separation.
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| 5. |
- Ahlberg, Jörgen, 1971-, et al.
(författare)
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Efficient active appearance model for real-time head and facial feature tracking
- 2003
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Ingår i: Analysis and Modeling of Faces and Gestures, 2003. AMFG 2003. IEEE International Workshop on. - : IEEE conference proceedings. - 0769520103 ; , s. 173-180
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Konferensbidrag (refereegranskat)abstract
- We address the 3D tracking of pose and animation of the human face in monocular image sequences using active appearance models. The classical appearance-based tracking suffers from two disadvantages: (i) the estimated out-of-plane motions are not very accurate, and (ii) the convergence of the optimization process to desired minima is not guaranteed. We aim at designing an efficient active appearance model, which is able to cope with the above disadvantages by retaining the strengths of feature-based and featureless tracking methodologies. For each frame, the adaptation is split into two consecutive stages. In the first stage, the 3D head pose is recovered using robust statistics and a measure of consistency with a statistical model of a face texture. In the second stage, the local motion associated with some facial features is recovered using the concept of the active appearance model search. Tracking experiments and method comparison demonstrate the robustness and out-performance of the developed framework.
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| 6. |
- Ahlberg, Jörgen, 1971-
(författare)
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Estimating atmosphere parameters in hyperspectral data
- 2010
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Ingår i: Proc. SPIE 7695, Algorithms and Technologies for Multispectral, Hyperspectral, and Ultraspectral Imagery XVI. - : SPIE - International Society for Optical Engineering. ; , s. Art.nr. 7695-82-
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Konferensbidrag (refereegranskat)abstract
- We address the problem of estimating atmosphere parameters (temperature, water vapour content) from data captured by an airborne thermal hyperspectral imager, and propose a method based on direct optimization. The method also involves the estimation of object parameters (temperature and emissivity) under the restriction that the emissivity is constant for all wavelengths. Certain sensor parameters can be estimated as well in the same process. The method is analyzed with respect to sensitivity to noise and number of spectral bands. Simulations with synthetic signatures are performed to validate the analysis, showing that estimation can be performed with as few as 10-20 spectral bands at moderate noise levels. More than 20 bands does not improvethe estimates. The proposedmethod is alsoextended to incorporateadditionalknowledge,for examplemeasurements ofatmospheric parameters and sensor noise.
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| 7. |
- Ahlberg, Jörgen, 1971-, et al.
(författare)
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Evaluating Template Rescaling in Short-Term Single-Object Tracking
- 2015
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Konferensbidrag (refereegranskat)abstract
- In recent years, short-term single-object tracking has emerged has a popular research topic, as it constitutes the core of more general tracking systems. Many such tracking methods are based on matching a part of the image with a template that is learnt online and represented by, for example, a correlation filter or a distribution field. In order for such a tracker to be able to not only find the position, but also the scale, of the tracked object in the next frame, some kind of scale estimation step is needed. This step is sometimes separate from the position estimation step, but is nevertheless jointly evaluated in de facto benchmarks. However, for practical as well as scientific reasons, the scale estimation step should be evaluated separately – for example,theremightincertainsituationsbeothermethodsmore suitable for the task. In this paper, we describe an evaluation method for scale estimation in template-based short-term single-object tracking, and evaluate two state-of-the-art tracking methods where estimation of scale and position are separable.
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| 8. |
- Ahlberg, Jörgen, 1971-, et al.
(författare)
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Facial Action Tracking
- 2011. - 2
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Ingår i: Handbook of Face Recognition. - London : Springer London. - 9780857299314 - 9780857299321 ; , s. 461-486
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Bokkapitel (refereegranskat)abstract
- This chapter explains the basics of parametric face models used for face and facial action tracking as well as fundamental strategies and methodologies for tracking. A few tracking algorithms serving as pedagogical examples are described in more detail.
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| 9. |
- Ahlberg, Jörgen, 1971-, et al.
(författare)
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Ground Target Recognition in a Query-Based Multi-Sensor Information System
- 2006
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- We present a system covering the complete process for automatic ground target recognition, from sensor data to the user interface, i.e., from low level image processing to high level situation analysis. The system is based on a query language and a query processor, and includes target detection, target recognition, data fusion, presentation and situation analysis. This paper focuses on target recognition and its interaction with the query processor. The target recognitionis executed in sensor nodes, each containing a sensor and the corresponding signal/image processing algorithms. New sensors and algorithms are easily added to the system. The processing of sensor data is performed in two steps; attribute estimation and matching. First, several attributes, like orientation and dimensions, are estimated from the (unknown but detected) targets. These estimates are used to select the models of interest in a matching step, where the targetis matched with a number of target models. Several methods and sensor data types are used in both steps, and data is fused after each step. Experiments have been performed using sensor data from laser radar, thermal and visual cameras. Promising results are reported, demonstrating the capabilities of the target recognition algorithms, the advantages of the two-level data fusion and the query-based system.
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| 10. |
- Ahlberg, Jörgen, 1971-
(författare)
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Model-based coding : extraction, coding, and evaluation of face model parameters
- 2002
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis deals with model-based coding of human faces for low bitrate communication. The basicidea of model-based coding is that the appearance and motion of a human face are analysed. By thisanalysis, compact parameters allowing realistic visualization of a synthetic face are extracted. The parameterscan be transmitted at very low bitrates, potentially allowing video face-to-face communicationover narrow channels like GSM or PSTN. Recently, numerous web-based applications for animatedfaces have emerged as well.Although the idea is two decades old by now, there are still several technical problems to be solved,and some of them are treated in this thesis. With the advent of the MPEG-4 standard for face animationwhich provides a standardized way for storing and transmitting animation parameters, model-basedcoding and face animation have been increasingly popular research topics.The first topic treated here is th ecompression of face model parameters. We propose a new compressionscheme, showing that such parameters can be transmitted with reasonable quality at bitrates lowerthan 1 kbit/s.Then, techniques for analysis of images and image sequences containing a human face are treated. Forstatic face images, a method for the extraction of facial features is proposed. For image sequences, amethod for face tracking using the active appearance model search algorithmis proposed and foundto be useful in practical experiments. Methods for achieving real-time performance have been developed,and the robustness and accuracy are analysed.To set the analysis in the context of possible applications, different ways of video synthesis using theextracted parameters are discussed as well.Finally, we take a look at the synthesized face models. Comparing them to real video sequences, wetry to evaluate how well the synthetic face models can convey emotions. Standard data sets and performancemeasures are suggested.
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