1,721,098 research outputs found
PCAP module 2 in-depth study report: reflections on peer-assessment in astronautics group work
No full textModifications to SDS source code for medium-term risk analysis for satellite constellations
No full textIACAPA: modelling recognition and learning of people with an interactive activation and competition model
No full textSeveral attempts have been made to model the processes involved in face recognition in a biologically and psychologically plausible manner. The most successful of these attempts used an interactive activation and competition (IAC) architecture. Here, the IAC architecture is extended to model acquisition as well as recognition of people, and the influence of name provision on the learning process is examined
Empirical models for estimating land cover areas from remotely sensed imagery
No full textThe mapping of land cover and land use is a key application of remotely sensed data. Traditionally, classification techniques are used to assign every pixel of an image to one of a number of mutually exclusive land cover classes. Alternatively, a modelling approach assigns to every pixel the area proportion containing each land cover class. This paper examines the hypothesis that the area modelling, or area estimation, approach can offer a richer and qualitatively more accurate representation of the true land cover than can be provided by the traditional classification approach. The paper describes the empirical, non-linear classifiers and area estimation models, based on neural networks and nearest neighbour algorithms, that have been developed to investigate this hypothesis. The algorithms were applied to an area-labelled Landsat TM data set produced as part of the EU FLIERS Project. The results demonstrated that a better representation of the true land cover was obtained using the area estimation models compared to the representation produced by the classification algorithms when the size of the land cover objects on the ground was less than the resolution of the sensor. These results are presented with a discussion of the evaluation issues involved with area estimatio
FLIERS software framework and toolkit version 2.0: user guides
No full textThis document describes how to run and use the FLIERS Software Framework and Toolkit (SFT) Version 2.0. The User Guide is divided into three main sections:A guide for running the FLIERS Software from the command-line and from an interactive environment.
A reference guide for keywords and operations that are found in Task and Process configuration files.
A worked example that explains how to create Task and Process configuration files to meet specific requirements.The User Guide should be read together with the Installation Guide and the Developer’s Guide for instructions on how to download and install the software and a guide to extending the software toolkit
An assessment of CubeSat collision risk
No full textIn their 2011 paper, Oltrogge and Leveque encouraged the CubeSat community to take leadership roles in space debris assessment, ensuring that debris guidelines and standards are met and by implementing effective debris mitigation strategies. However, common misconceptions about the role of CubeSats in the evolution of the space debris environment remain today. For example, up to two-thirds of all CubeSats launched to-date are predicted to remain on-orbit for more than 25 years. In addition, CubeSats have contributed more than 360,000 unique events since November 2005 to the record of satellite conjunctions produced by Celestrak’s Satellite Orbital Conjunction Reports Assessing Threatening Encounters in Space (SOCRATES). To provide some clarity on this issue, a database of CubeSats containing their launch history and relevant physical parameters has been developed for use within the Debris Analysis and Monitoring Architecture to the Geosynchronous Environment (DAMAGE), which has been employed to assess the future collision risk from CubeSats. The probability and likely characteristics of conjunctions involving CubeSats have been estimated for a 30-year projection from 1 January 2013 of the low Earth orbit (LEO) population of objects ? 10 cm. Three CubeSat launch traffic scenarios were modelled using Gompertz logistic functions with maximum launch rates of 205, 560 and 700 CubeSats per year. These CubeSat launches were added to regular launch traffic, which was based on historical launches from the period 2005 to 2012. Further, calibration of DAMAGE conjunction predictions for the historical period 2005 to 2013 with those recorded by SOCRATES enabled the true number of conjunctions involving CubeSats to be estimated for the future projections. Results show that, even for a relatively low launch rate, CubeSats are anticipated to be involved in 16.5 to 165 million conjunctions in the next 30 years and, potentially, catastrophic collisions as early as 2014. Whilst CubeSats are relatively small, they are nevertheless involved in high-speed conjunctions with large, resident LEO spacecraft and debris in SOCRATES and DAMAGE predictions. To reduce the risks, some effort is needed to engage with the growing small satellite community, and to encourage them to contribute to and, ultimately, lead on sustainable practices and debris mitigation activitie
A generalized confusion matrix for assessing area estimates from remote sensing imagery
No full textThe formulation of a generalized area-based confusion matrix for exploring the accuracy of area estimates is presented. The generalized confusion matrix is appropriate for both traditional classification algorithms and sub-pixel area estimation models. An error matrix, derived from the generalized confusion matrix, allows the accuracy of maps generated using area estimation models to be assessed quantitatively and compared to the accuracies obtained from traditional classification techniques. The application of this approach is demonstrated for an area estimation model applied to Landsat data of an urban area of the United Kingdom
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