19 results
Search Results
2. Development of an algorithm for identification of sown biodiverse pastures in Portugal.
- Author
-
Morais, Tiago G., Rodrigues, Nuno R., Gama, Ivo, Domingos, Tiago, and Teixeira, Ricardo F.M.
- Subjects
ARTIFICIAL neural networks ,MACHINE learning ,ALGORITHMS ,SOWING ,PASTURES - Abstract
Sown biodiverse pastures (SBP) are a pasture system developed in Portugal. Until 2014, farmers were supported in installing and maintaining SBP, but tracking their locations has been lacking. To survey the country, remote sensing tools with machine learning were used. Here, we developed the first algorithm that combines remote sensing data with machine learning algorithms to identify SBP areas. The algorithm combines Landsat-7 and night-light spectral data with terrain and bioclimatic data. Remotely sensed data offer higher spatial resolution compared to bioclimatic data and also cover interannual variability. Gradient-boosted decision trees (XGB) and artificial neural networks (ANN) were the machine learning methods used. The overall classification accuracy, on an independent validation dataset, was 94%, with 82% producer accuracy and 85% user accuracy. The total estimated area of SBP in the Portuguese region of Alentejo region was 1300 km2 in 2013, which is similar to the total known installed area (approximately 1000 km
2 ). The estimated spatial distribution is in accordance with the known distribution at the municipal level. These results are a critical first step towards the future development of remote systems for assessing the state of SBP and for compliance checks of farmer commitments. [ABSTRACT FROM AUTHOR]- Published
- 2023
- Full Text
- View/download PDF
3. Algorithm for the Reconstruction of the Ground Surface Reflectance in the Visible and Near IR Ranges from MODIS Satellite Data with Allowance for the Influence of Ground Surface Inhomogeneity on the Adjacency Effect and of Multiple Radiation Reflection.
- Author
-
Tarasenkov, Mikhail V., Belov, Vladimir V., Engel, Marina V., Zimovaya, Anna V., Zonov, Matvei N., and Bogdanova, Alexandra S.
- Subjects
SURFACE reconstruction ,REFLECTANCE ,ATMOSPHERIC turbidity ,VISIBLE spectra ,RADIATION ,INFRARED radiation ,ALGORITHMS - Abstract
An atmospheric correction algorithm is proposed for the reconstruction of the ground surface reflectance from the data of satellite measurements. A distinctive feature of the algorithm is that it takes into account the influence of the ground surface inhomogeneity on the adjacency effect and additional illumination of the ground surface by reflected radiation. These factors are important for the reconstruction of the reflectance of ground surface fragments with sharp reflectance changes and high atmospheric turbidity. The algorithm is based on Monte Carlo programs developed by the authors. To reduce the computing time, we have proposed some original criteria and approaches. To estimate the capabilities of the developed algorithm, its results have been validated by comparing with the results of the MOD09 algorithm for four MODIS bands and measurements for the Portugal surface fragment with coordinates 38.829 N, 8.791 W. Good agreement of the results obtained by the proposed algorithm with the surface measurements and the data obtained by the MOD09 algorithm demonstrates the efficiency of the proposed algorithm in the reconstruction of the ground surface reflectance. [ABSTRACT FROM AUTHOR]
- Published
- 2023
- Full Text
- View/download PDF
4. ARTIFICIAL INTELLIGENCE AND JOURNALISM: AN APPROACH TO THE PORTUGUESE CONTEXT.
- Author
-
GONÇALVES, Adriana and MELO, Paulo Victor
- Subjects
ARTIFICIAL intelligence ,NEWSPAPER circulation ,JOURNALISM ,ELECTRONIC newspapers ,TRAINING needs ,JOURNALISTS - Abstract
Copyright of Fonseca: Journal of Communication is the property of Revista Fonseca Journal of Communication and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)
- Published
- 2022
- Full Text
- View/download PDF
5. A multidimensional perspective of the relation between social isolation and depression among Portuguese older adults.
- Author
-
Henriques, Ana, Talih, Makram, Pastor‐Valero, Maria, Fraga, Sílvia, Dias, Isabel, Matijasevich, Alicia, and Barros, Henrique
- Subjects
SOCIAL support ,CONFIDENCE intervals ,CROSS-sectional method ,MULTIVARIATE analysis ,INTERVIEWING ,GERIATRIC Depression Scale ,SOCIAL isolation ,SOCIOECONOMIC factors ,SEX distribution ,COMPARATIVE studies ,MENTAL depression ,INDEPENDENT living ,QUESTIONNAIRES ,SCALE analysis (Psychology) ,SENSITIVITY & specificity (Statistics) ,CLUSTER analysis (Statistics) ,LOGISTIC regression analysis ,DATA analysis software ,ODDS ratio ,LONGITUDINAL method ,ALGORITHMS - Abstract
We aimed to explore how different social isolation components were associated with depression among older adults in Portugal. We analysed data collected through structured questionnaires in 2017 from 643 Portuguese adults aged 60 and over. Depression was assessed using the Geriatric Depression Scale (Short‐Form). Social isolation was operationalised using objective indicators – living alone, marital status, leisure activities – and subjective indicator – perceived social support. Because social isolation is a multidimensional construct that is likely to be more than the sum of its components, cluster analysis was conducted to group individuals into social isolation profiles. Associations were estimated using adjusted odds ratios (ORs) and 95% confidence intervals (CIs). Five profiles were identified: Cluster 1 (partnered; high social support; high variety of leisure activities); Cluster 2 (partnered; high social support; few leisure activities); Cluster 3 (not partnered; low social support; few leisure activities); Cluster 4 (living alone; high social support; high variety of leisure activities); Cluster 5 (partnered; high social support; limited variety of leisure activities). Compared with Cluster 1, participants in Cluster 2 were three times more likely to have depression, independent of age, gender, education, comorbidities and self‐rated health (OR = 3.04; 95% CI: 1.38–6.71). Participants in Cluster 3 presented the highest probability of depression that was not explained by any of the confounders (OR = 4.74; 95% CI: 2.15–10.44). Older adults living alone are not necessarily more prone to depression, with social support and leisure activities playing an important role. To disentangle how social isolation affects health, objective and subjective isolation measures should be considered. [ABSTRACT FROM AUTHOR]
- Published
- 2022
- Full Text
- View/download PDF
6. AIS Based Shipping Routes Using the Dijkstra Algorithm.
- Author
-
Silveira, P., Teixeira, A. P., and Soares, C. Guedes
- Subjects
AUTOMATIC identification ,SYSTEM identification ,ALGORITHMS ,GRID cells ,CELL motility ,CONTAINER ships ,SHIPPING containers - Abstract
This paper proposes an approach for identifying and characterizing shipping routes using information contained in Automatic Identification System messages broadcasted by ships and recorded by the coastal Vessel Traffic Service centre. The approach consists of using historical Automatic Identification System data to build a graph, where nodes are cells of a grid covering the geographical area being studied and the weights of directional edges are inversely related to ship movements between cells. Based on this graph, the Dijkstra algorithm is used to identify a potential safe route, assumed to be the most used route by ships between two locations. A second graph is created simultaneously, with the same nodes and edges, but with edge weights equal to the average speed of transitions between cells, thus allowing the determination of the average speed profile for any possible path within the graph. The proposed approach is applied to two scenarios: an approach to the port of Lisbon and the entry through the fairway to a RO-RO terminal in the port of Setubal in Portugal. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
7. Impact of Ensemble Learning in the Assessment of Skeletal Maturity.
- Author
-
Cunha, Pedro, Moura, Daniel, Guevara López, Miguel, Guerra, Conceição, Pinto, Daniela, and Ramos, Isabel
- Subjects
SKELETAL maturity ,ACADEMIC medical centers ,ALGORITHMS ,DIAGNOSTIC imaging ,COMPUTERS in medicine ,REGRESSION analysis ,RESEARCH funding ,DICOM (Computer network protocol) ,CHILDREN - Abstract
The assessment of the bone age, or skeletal maturity, is an important task in pediatrics that measures the degree of maturation of children's bones. Nowadays, there is no standard clinical procedure for assessing bone age and the most widely used approaches are the Greulich and Pyle and the Tanner and Whitehouse methods. Computer methods have been proposed to automatize the process; however, there is a lack of exploration about how to combine the features of the different parts of the hand, and how to take advantage of ensemble techniques for this purpose. This paper presents a study where the use of ensemble techniques for improving bone age assessment is evaluated. A new computer method was developed that extracts descriptors for each joint of each finger, which are then combined using different ensemble schemes for obtaining a final bone age value. Three popular ensemble schemes are explored in this study: bagging, stacking and voting. Best results were achieved by bagging with a rule-based regression (M5P), scoring a mean absolute error of 10.16 months. Results show that ensemble techniques improve the prediction performance of most of the evaluated regression algorithms, always achieving best or comparable to best results. Therefore, the success of the ensemble methods allow us to conclude that their use may improve computer-based bone age assessment, offering a scalable option for utilizing multiple regions of interest and combining their output. [ABSTRACT FROM AUTHOR]
- Published
- 2014
- Full Text
- View/download PDF
8. A traffic analysis zone definition: a new methodology and algorithm.
- Author
-
Martínez, Luis M., Viegas, José Manuel, and Silva, Elisabete A.
- Subjects
TRANSPORTATION ,ALGORITHMS ,URBAN growth - Abstract
This paper develops a comprehensive approach to the definition of transportation analysis zones (TAZ), and therein, presents a new methodology and algorithm for the definition of TAZ embedded in geographic information systems software, improves the base algorithm with several local algorithms, and comprehensively analyses the obtained results. The results obtained are then compared to these presently used in the transportation analysis process of the Lisbon Metropolitan Area. The proposed algorithm presents a new methodology for TAZ design based on a smoothed density surface of geocoded travel demand data. The algorithm aims to minimise the loss of information when moving from a continuous representation of the origin and destination of each trip to their discrete representations through zones, and focuses on the trade-off between the statistical precision, geographical error, and the percentage of intra-zonal trips of the resulting OD matrix. The results for the Lisbon Metropolitan Area case study suggest a significant improvement in OD matrix estimates compared to current transportation analysis practises based on administrative units. [ABSTRACT FROM AUTHOR]
- Published
- 2009
- Full Text
- View/download PDF
9. Adaptation and validation to Portuguese of the Reasons for Higher Education Dropout Scale.
- Author
-
Ferreira, Manuela, Duarte, João, Abrantes, José Luís, Cabral, Lídia, Guiné, Raquel, Campos, Sofia, and Cardoso, Ana Paula
- Subjects
ADAPTABILITY (Personality) ,ALGORITHMS ,COLLEGE students ,STATISTICAL correlation ,DISCRIMINANT analysis ,SCHOOL dropouts ,FACTOR analysis ,GOODNESS-of-fit tests ,RESEARCH methodology ,MULTIVARIATE analysis ,PSYCHOMETRICS ,QUESTIONNAIRES ,RESEARCH ,RESEARCH evaluation ,STATISTICAL sampling ,STATISTICS ,QUANTITATIVE research ,SOCIOECONOMIC factors ,LATENT semantic analysis ,RESEARCH methodology evaluation ,DATA analysis software ,DESCRIPTIVE statistics - Abstract
Copyright of Revista de Enfermagem Referência is the property of Escola Superior de Enfermagem de Coimbra and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)
- Published
- 2019
- Full Text
- View/download PDF
10. Do women in Europe live longer and happier lives than men?.
- Author
-
Solé-Auró, Aïda, Jasilionis, Domantas, Li, Peng, and Oksuzyan, Anna
- Subjects
ALGORITHMS ,HAPPINESS ,LIFE expectancy ,RETIREMENT ,SATISFACTION ,SEX distribution ,SURVEYS ,PSYCHOLOGY of women ,ATTITUDES toward death ,DISEASE prevalence - Abstract
Background The article examines gender differences in happy life expectancy at age 50 (LE50) and computes the age-specific contributions of mortality and happiness effects to gender differences in happy LE50 in 16 European countries. Methods Abridged life tables and happy LE50 were calculated using conventional life tables and Sullivan's method. Age-specific death rates were calculated from deaths and population exposures in the Human Mortality Database. Happiness prevalence was estimated using the 2010–11 Survey of Health, Ageing and Retirement in Europe. Happiness was defined using a single question about life satisfaction on a scale of 0–10. A decomposition algorithm was applied to estimate the exact contributions of the differences in mortality and happiness to the overall gender gap in happy LE50. Results Gender differences in happy LE50 favour women in all countries except Portugal (0.43 years in Italy and 3.55 years in Slovenia). Generally, the contribution of the gender gap in happiness prevalence is smaller than the one in mortality. The male advantage in the prevalence of happiness partially offsets the effects of the female advantage in mortality on the total gender gap in happy LE50. Gender differences in unhappy life years make up the greatest share of the gender gap in total LE50 in all countries except Denmark, Germany, Netherlands, Slovenia and Sweden. Conclusion Countries with the largest gender gap in LE are not necessarily the countries with larger differences in happy LE50. The remaining years of life of women are expected to be spent not only in unhealthy but also in unhappy state. [ABSTRACT FROM AUTHOR]
- Published
- 2018
- Full Text
- View/download PDF
11. Contribution of Geographic Information Systems and location models to planning of wastewater systems.
- Author
-
Leitão, J. P., Matos, J. S., Gonçalves, A. B., and Matos, J. L.
- Subjects
SEWAGE disposal plant design & construction ,SEWERAGE ,GEOGRAPHIC information systems ,SPATIAL analysis (Statistics) ,MATHEMATICAL optimization ,ALGORITHMS ,INFORMATION resources management software ,CASE studies - Abstract
This paper presents the contributions of Geographic Information Systems (GIS) and location models towards planning regional wastewater systems (sewers and wastewater treatment plants) serving small agglomerations, i.e. agglomerations with less than 2,000 inhabitants. The main goal was to develop a decision support tool for tracing and locating regional wastewater systems. The main results of the model are expressed in terms of number, capacity and location of Wastewater Treatment Plants (WWTP) and the length of main sewers. The decision process concerning the location and capacity of wastewater systems has a number of parameters that can be optimized. These parameters include the total sewer length and number, capacity and location of WWTP. The optimization of parameters should lead to the minimization of construction and operation costs of the integrated system. Location models have been considered as tools for decision support, mainly when a geo-referenced database can be used. In these cases, the GIS may represent an important role for the analysis of data and results especially in the preliminary stage of planning and design. After selecting the spatial location model and the heuristics, two greedy algorithms were implemented in Visual Basic for Applications® on the ArcGIS® software environment. To illustrate the application of these algorithms a case study was developed, in a rural area located in the central part of Portugal. [ABSTRACT FROM AUTHOR]
- Published
- 2005
12. Atmospheric driving mechanisms of flash floods in Portugal.
- Author
-
Santos, Mónica, Santos, João A., and Fragoso, Marcelo
- Subjects
ATMOSPHERIC circulation ,FLOODS ,METEOROLOGICAL precipitation ,ATMOSPHERIC pressure ,ALGORITHMS - Abstract
ABSTRACT The present study aims to investigate how large-scale atmospheric circulation may influence flash floods in Portugal. For this purpose, weather types ( WTs) in a northeastern North Atlantic sector are used and flash floods between 1950 and 2003 were identified in six hydrographic basins: three in the north of Portugal and another three in the south of Portugal. An adapted methodology for flash flood detection on daily discharges is applied. A total of 131 flash floods were detected: 35 in the northern basins and 96 in the southern basins. WTs are identified using the National Oceanic and Atmospheric Administration 20th Century Reanalysis V2. The sea level pressure composites for flash flood days by WT reveal the large-scale atmospheric patterns underlying their occurrence. The results show that the cyclonic (C) type was strongly associated with flash flood days in the northern basins. The C type pattern features deep low pressure systems north of Iberia, much stronger than average for this WT. For the southern basins, the C type still shows the highest relevance for flood occurrence, but to a lesser extent, since the easterly wind (E) and dual anticyclonic ( AA) types also acquire some importance. The flash flood-inducing AA-type events are characterized by atypical largely zonal troughs extending towards Portugal. The flash flood-inducing E type events hint at the occurrence of anomalously strong cut-off low pressure systems over southern Portugal. Although the significance of these systems to precipitation in Portugal was addressed in previous studies, a systematized assessment of their role on flash flood occurrences is herein provided for the first time. The presented flash flood detection methodology can be applied to other regions where hourly flow discharge data are not available, thus being an alternative to the more conventional detection algorithms. [ABSTRACT FROM AUTHOR]
- Published
- 2017
- Full Text
- View/download PDF
13. Risk Trajectories of Self-Destructiveness in Adolescence: Family Core Influences.
- Author
-
Cruz, Diana, Narciso, Isabel, Pereira, Cícero, and Sampaio, Daniel
- Subjects
SELF-mutilation ,ALGORITHMS ,ATTACHMENT behavior ,CHI-squared test ,FACTOR analysis ,PARENTING ,QUESTIONNAIRES ,RISK-taking behavior ,SCALE analysis (Psychology) ,SELF-evaluation ,FAMILY relations ,STRUCTURAL equation modeling ,DESCRIPTIVE statistics ,ADOLESCENCE ,RISK factors of self-injurious behavior - Abstract
The study of family factors, (namely, parenting, attachment and family functioning) that can either reduce or increase risk factors during adolescent development is crucial to the early identification of adolescents at risk for self-destructive thoughts and behaviors (SDTB). Altough several studies have highlighted the role of family factors, few have analysed the joint impact of parenting styles and attachment in SDT. This study aimed to: (1) to identify the dimensions of parenting styles and parental attachment that predict SDTB; (2) to determine the mediation effect of cohesion on the relation between these predictors and reports of SDTB; and (3) to analyze sex and age differences in the abovementioned process. Participants included 1,266 Portuguese adolescents with a mean age of 15.9 years. Structural equation modeling demonstrated that paternal and maternal rejection and paternal control were the most accurate predictors of SDTB, emphasizing their role as risk factors for maladaptive trajectories with reports of SDTB. Results clearly emphasized the relevancy of the fathers' role in such maladaptive trajectories. Additionally, a mediation effect of cohesion and a moderation of sex were also found. This study highlights the importance of intervening with the family in preventive and therapeutic contexts regarding adolescents' well-being and their relationship with parents. [ABSTRACT FROM AUTHOR]
- Published
- 2014
- Full Text
- View/download PDF
14. Implementation of the Nursing Role Effectiveness Model.
- Author
-
Salgueiro, Antonio Fernando, Lopes Fereira, Pedro, Lucilia Cardoso, Maria, and Vidinha, Telma
- Subjects
ALGORITHMS ,ANALYSIS of variance ,CHI-squared test ,CONCEPTUAL structures ,STATISTICAL correlation ,LONGITUDINAL method ,MEDICAL quality control ,NURSES ,NURSES' attitudes ,NURSING ,NURSING models ,QUESTIONNAIRES ,REGRESSION analysis ,RESEARCH funding ,SCALE analysis (Psychology) ,HEALTH self-care ,OCCUPATIONAL roles ,STRUCTURAL equation modeling ,CROSS-sectional method ,DATA analysis software ,PATIENTS' attitudes - Abstract
Given the economic constraints and efforts to achieve efficiency and effectiveness in health care systems, nurses' contribution should be analyzed. The Nursing Role Effectiveness Model examines nurses' contribution to health care based on specific relationships between structure, process and outcome variables. A cross-sectional and longitudinal study was carried out in 26 units of four hospitals in the central region of Portugal to test this model. A total sample of 1764 patients and 364 nurses was obtained. Data were analyzed using SPSS and AMOS 21. The relationships between the variables were tested using the Structural Equation Modelling, indicating a good data fit and statistical significance. In addition to assessing nurses' contribution, this model underlines the value and effectiveness of nursing care. [ABSTRACT FROM AUTHOR]
- Published
- 2014
15. Predicting onset of major depression in general practice attendees in Europe: extending the application of the predictD risk algorithm from 12 to 24 months.
- Author
-
King, M., Bottomley, C., Bellón-Saameño, J., Torres-Gonzalez, F., Švab, I., Rotar, D., Xavier, M., and Nazareth, I.
- Subjects
ALGORITHMS ,CONFIDENCE intervals ,MENTAL depression ,FAMILY medicine ,LONGITUDINAL method ,QUESTIONNAIRES ,RESEARCH funding ,RISK assessment ,DATA analysis software - Abstract
BackgroundPredictD is a risk algorithm that was developed to predict risk of onset of major depression over 12 months in general practice attendees in Europe and validated in a similar population in Chile. It was the first risk algorithm to be developed in the field of mental disorders. Our objective was to extend predictD as an algorithm to detect people at risk of major depression over 24 months.MethodParticipants were 4190 adult attendees to general practices in the UK, Spain, Slovenia and Portugal, who were not depressed at baseline and were followed up for 24 months. The original predictD risk algorithm for onset of DSM-IV major depression had already been developed in data arising from the first 12 months of follow-up. In this analysis we fitted predictD to the longer period of follow-up, first by examining only the second year (12–24 months) and then the whole period of follow-up (0–24 months).ResultsThe instrument performed well for prediction of major depression from 12 to 24 months [c-index 0.728, 95% confidence interval (CI) 0.675–0.781], or over the whole 24 months (c-index 0.783, 95% CI 0.757–0.809).ConclusionsThe predictD risk algorithm for major depression is accurate over 24 months, extending it current use of prediction over 12 months. This strengthens its use in prevention efforts in general medical settings. [ABSTRACT FROM AUTHOR]
- Published
- 2013
- Full Text
- View/download PDF
16. An international risk prediction algorithm for the onset of generalized anxiety and panic syndromes in general practice attendees: predictA.
- Author
-
King, M., Bottomley, C., Bellón-Saameño, J. A., Torres-Gonzalez, F., Švab, I., Rifel, J., Maaroos, H.-I., Aluoja, A., Geerlings, M. I., Xavier, M., Carraça, I., Vicente, B., Saldivia, S., and Nazareth, I.
- Subjects
PANIC disorders ,AGE factors in disease ,ANXIETY disorders ,ALGORITHMS ,CONFIDENCE intervals ,INTERVIEWING ,LONGITUDINAL method ,PRIMARY health care ,RISK assessment ,MATHEMATICAL variables ,LOGISTIC regression analysis ,DATA analysis software ,PREVENTION ,MENTAL illness risk factors - Abstract
BackgroundThere are no risk models for the prediction of anxiety that may help in prevention. We aimed to develop a risk algorithm for the onset of generalized anxiety and panic syndromes.MethodFamily practice attendees were recruited between April 2003 and February 2005 and followed over 24 months in the UK, Spain, Portugal and Slovenia (Europe4 countries) and over 6 months in The Netherlands, Estonia and Chile. Our main outcome was generalized anxiety and panic syndromes as measured by the Patient Health Questionnaire. We entered 38 variables into a risk model using stepwise logistic regression in Europe4 data, corrected for over-fitting and tested it in The Netherlands, Estonia and Chile.ResultsThere were 4905 attendees in Europe4, 1094 in Estonia, 1221 in The Netherlands and 2825 in Chile. In the algorithm four variables were fixed characteristics (sex, age, lifetime depression screen, family history of psychological difficulties); three current status (Short Form 12 physical health subscale and mental health subscale scores, and unsupported difficulties in paid and/or unpaid work); one concerned country; and one time of follow-up. The overall C-index in Europe4 was 0.752 [95% confidence interval (CI) 0.724–0.780]. The effect size for difference in predicted log odds between developing and not developing anxiety was 0.972 (95% CI 0.837–1.107). The validation of predictA resulted in C-indices of 0.731 (95% CI 0.654–0.809) in Estonia, 0.811 (95% CI 0.736–0.886) in The Netherlands and 0.707 (95% CI 0.671–0.742) in Chile.ConclusionsPredictA accurately predicts the risk of anxiety syndromes. The algorithm is strikingly similar to the predictD algorithm for major depression, suggesting considerable overlap in the concepts of anxiety and depression. [ABSTRACT FROM PUBLISHER]
- Published
- 2011
- Full Text
- View/download PDF
17. Operational cloud classification for the Iberian Peninsula using Meteosat Second Generation and AQUA-AIRS image fusion.
- Author
-
Casanova, C., Romo, A., Hernández, E., and Casanova, J.L.
- Subjects
TELECOMMUNICATION satellites ,SPECTROPHOTOMETERS ,DETECTORS ,SPECTRORADIOMETER ,ALGORITHMS ,SPECTROSCOPE ,TELECOMMUNICATION ,ARTIFICIAL satellites - Abstract
The aim of this work was the adaptation and improvement of a previous cloud detection and classification algorithm that was developed for the Meteosat-7 satellite. The functions of this satellite have now been taken on by the new series of Meteosat Second Generation (MSG) satellites, which are not just replicas but new, much improved versions of their predecessor. The formerly used Advanced/Tiros-N Operational Vertical Sounder (A/TOVS) probe has also been superseded technologically by new sensors with better spatial resolution, capable of carrying out more accurate measurements at a greater number of wavelengths. This is the case of the Moderate Resolution Imaging Spectroradiometer (MODIS) sensor onboard the TERRA and AQUA satellites and of the Atmospheric Infrared Sounder (AIRS) probe. In this context, new potential improvements are analysed for this algorithm by using these new platforms and sensors and the results are compared to those obtained in the first classification. [ABSTRACT FROM AUTHOR]
- Published
- 2010
- Full Text
- View/download PDF
18. Effects of species and habitat positional errors on the performance and interpretation of species distribution models.
- Author
-
Osborne, Patrick E. and Leitão, Pedro J.
- Subjects
BIRDS ,HABITATS ,SPECIES ,DIGITAL images ,INFORMATION processing ,SPACE surveillance ,AUTOCORRELATION (Statistics) ,ALGORITHMS - Abstract
Aim A key assumption in species distribution modelling is that both species and environmental data layers contain no positional errors, yet this will rarely be true. This study assesses the effect of introduced positional errors on the performance and interpretation of species distribution models. Location Baixo Alentejo region of Portugal. Methods Data on steppe bird occurrence were collected using a random stratified sampling design on a 1-km
2 pixel grid. Environmental data were sourced from satellite imagery and digital maps. Error was deliberately introduced into the species data as shifts in a random direction of 0–1, 2–3, 4–5 and 0–5 pixels. Whole habitat layers were shifted by 1 pixel to cause mis-registration, and the cumulative effect of one to three shifted layers investigated. Distribution models were built for three species using three algorithms with three replicates. Test models were compared with controls without errors. Results Positional errors in the species data led to a drop in model performance (larger errors having larger effects – typically up to 10% drop in area under the curve on average), although not enough for models to be rejected. Model interpretation was more severely affected with inconsistencies in the contributing variables. Errors in the habitat layers had similar although lesser effects. Main conclusions Models with species positional errors are hard to detect, often statistically good, ecologically plausible and useful for prediction, but interpreting them is dangerous. Mis-registered habitat layers produce smaller effects probably because shifting entire layers does not break down the correlation structure to the same extent as random shifts in individual species observations. Spatial autocorrelation in the habitat layers may protect against species positional errors to some extent but the relationship is complex and requires further work. The key recommendation must be that positional errors should be minimised through careful field design and data processing. [ABSTRACT FROM AUTHOR]- Published
- 2009
- Full Text
- View/download PDF
19. Effects of climate change on the distribution of Iberian tree species.
- Author
-
Benito Garzón, Marta, Sánchez de Dios, Rut, and Sainz Ollero, Helios
- Subjects
CLIMATE change ,MULTIPURPOSE trees ,FOREST dynamics ,FOREST ecology ,ALGORITHMS - Abstract
Question: Will the predicted climate changes affect species distribution in the Iberian Peninsula? Location: Iberian Peninsula (Spain and Portugal). Methods: We modelled current and future tree distributions as a function of climate, using a computational framework that made use of one machine learning technique, the random forest (RF) algorithm. This algorithm provided good predictions of the current distribution of each species, as shown by the area under the corresponding receiver operating characteristics (ROC) curves. Species turnover, richness and the change in distributions over time to 2080 under four Intergovernmental panel on climate change (IPCC) scenarios were calculated using the species map outputs. Results and Conclusions: The results show a notable reduction in the potential distribution of the studied species under all the IPCC scenarios, particularly so for mountain conifer species such as Pinus sylvestris, P. uncinata and Abies alba. Temperate species, especially Fagus sylvatica and Quercus petraea, were also predicted to suffer a reduction in their range; also sub-mediterranean species, especially Q. pyrenaica, were predicted to undergo notable decline. In contrast, typically Mediterranean species appeared to be generally more capable of migration, and are therefore likely to be less affected. [ABSTRACT FROM AUTHOR]
- Published
- 2008
- Full Text
- View/download PDF
Discovery Service for Jio Institute Digital Library
For full access to our library's resources, please sign in.