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Estudo comparativo entre dois métodos de calibração da pletismografia respiratória por indutância em individuos saudáveis; Comparative study between two methods of calibration of respiratory inductive plethysmography

Barbosa, Renata Cleia Claudino
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 13/06/2011 PT
Relevância na Pesquisa
36.78%
Nas últimas décadas, considerável atenção foi direcionada para os dispositivos de mensuração não invasiva da configuração e coordenação toracoabdominal. Dentre os dispositivos mais empregados, destaca-se aquele que emprega a Pletismografia Respiratória por Indutância (PRI) que, apesar de ser considerado um dispositivo de avaliação reprodutível e acurado, apresenta divergências acerca do método de calibração para estimativa da participação dos compartimentos torácico e abdominal, principalmente quando utilizada em diferentes posturas corporais. O padrão-ouro da calibração da PRI é o método de calibração por isovolume (ISOCAL). Entretanto, a grande maioria dos estudos emprega somente a calibração qualitativa diagnóstica (QDC) devido ao fato desta não necessitar manobras respiratórias específicas. Em vista disso, o objetivo deste estudo foi comparar os dois métodos de calibração da PRI, em 3 diferentes posturas (decúbito dorsal, sedestação e ortostatismo). Foram avaliados 28 indivíduos saudáveis (18 mulheres/10 homens), com idade de 25,4±3,9 anos (média±DP). Todos os indivíduos foram submetidos aos dois métodos de calibração (ISOCAL e QDC) e avaliados nas 03 posturas. Foi verificado que os valores da constante de proporcionalidade dos sinais elétricos dos compartimentos (K) foram distintos em ambos os métodos de calibração nas 3 posturas avaliadas. Os valores de K avaliados com a calibração ISOCAL e QDC foram...

Desenvolvimento de uma metodologia de calibração e testes de medidores de produto Kerma-Área; Development of a calibration methodology and tests of kerma area product meters

Costa, Nathalia Almeida
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 20/06/2013 PT
Relevância na Pesquisa
36.77%
A grandeza produto kerma-área (PKA) é importante para estabelecer níveis de referência em exames de radiologia diagnóstica. Essa grandeza pode ser obtida por meio de medidores do PKA. O uso desses medidores é fundamental para avaliar a dose de radiação em procedimentos radiológicos, além de ser um bom indicador para que os limites de dose na pele do paciente não sejam excedidos. Algumas vezes, esses medidores vêm acoplados a equipamentos de radiação X, o que dificulta sua calibração. Neste trabalho foi desenvolvida uma metodologia de calibração de medidores do PKA. O instrumento utilizado para este fim foi o Patient Dose Calibrator (PDC). Ele foi desenvolvido para ser utilizado como referência na verificação da calibração de medidores do PKA e kerma no ar usados na dosimetria de pacientes e para verificação da consistência e do comportamento de sistemas de controle de exposição automáticos. Por se tratar de um equipamento novo, que, no Brasil, ainda não é utilizado como equipamento de referência para calibração, foi realizado, também o controle de qualidade deste equipamento, com testes de caracterização, a calibração e a avaliação da dependência energética. Após os testes, ficou provado que o PDC pode ser utilizado como instrumento de referência para a calibração a ser realizada in situ...

Otimização de um sistema de controle e aquisição de dados para calibração de medidores de radiação X com utilização de ferramentas computacionais; Optimization of a data acquisition and control system for calibration of X rays detectors with usage of computational tools

Rodrigues, Yklys Santos
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 18/06/2013 PT
Relevância na Pesquisa
36.77%
A norma da ABNT ISO/IEC 17025/2005 especifica requerimentos gerais para competência de laboratórios de ensaio e calibração. Um destes requerimentos é que instalações desses tipos devem sempre ter seus processos otimizados e para tal é necessário que as incertezas envolvidas sejam estimadas e reduzidas o máximo possível. Para atingir tal quesito, o Laboratório de Calibração de Instrumentos (LCI), o laboratório responsável por calibrações de dosímetros no Instituto de Pesquisas Energéticas e Nucleares (IPEN/CNEN), tem adquirido vários equipamentos para suas instalações, e em especial para o Laboratório de Calibração de medidores de radiação X. Dentre estes aparelhos, destaca-se uma roda de posicionamento de filtros com acionamento automático e o uso de softwares de controle com o intuito de melhorar o processo de calibração reduzindo a ocorrência de erros limitando ao máximo, por exemplo, a necessidade de intervenção humana. Um sistema de controle e aquisição de dados para calibração de instrumentos semi-automatizado foi desenvolvido com LabVIEW e está sendo submetido a sucessivos testes e melhorias. O programa é dividido em dois módulos: um responsável pela calibração da câmara monitora com relação a um dosímetro padrão de referência e outro responsável por calibrações rotineiras utilizando a câmara monitora como padrão de referência. Grandezas que influenciam as medições também foram analisadas e as devidas correções foram implementadas no sistema. Além de adquirir dados e controlar equipamentos...

Detecção topológica de padrões xadrez para calibração de câmeras; Topological detection of chessboard patterns for camera calibration

Laureano, Gustavo Teodoro
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 23/08/2013 PT
Relevância na Pesquisa
36.77%
A identificação de pontos em padrões de calibração é relatada como uma fase trabalhosa nos processos de calibração de câmeras. Essa etapa é sensível à presença de ruídos e geralmente requer a identificação de muitos pontos de controle. A detecção automática de padrões de calibração é fundamental para a automatização desse processo. Os trabalhos existentes são poucos e implementam soluções semi-automáticas ou, quando automáticas, não lidam com imagens distorcidas, com inclinações acentuadas ou exigem a detecção de todos os pontos apresentados pelo padrão de calibração. O presente trabalho vem contribuir com essa área propondo uma metodologia, denominada Chessboard Topological Detection (ChTD), completamente automática, aplicável a imagens com alta distorção, independente da detecção completa do padrão e que apresenta melhor aproveitamento dos pontos e do conjunto de imagens de calibração. A metodologia proposta é baseada em três etapas: a detecção estrutural dos pontos de interesse; triangulação e filtragem dos pontos encontrados com base em regras topológicas; e a propagação e ajuste de coordenadas via conectividade dos pontos vizinhos. A partir dessa metodologia foi implementada uma ferramenta que permite extrair pontos de calibração de um padrão xadrez de forma simples e completamente automática. Na avaliação do método ChTD foi realizada uma comparação com a função findChessBoardCorners da biblioteca OpenCV usando conjuntos de imagens reais e sintéticas. Os testes realizados com imagens reais possibilitaram comparações numéricas da quantidade de pontos e de padrões detectados...

Desenvolvimento de um dispositivo auxiliar para calibração de bombas de roletes utilizadas em circulação extracorpórea; Development of an auxiliary device for calibration of roller pumps used in extracorporeal circulation

Johannes Dantas de Medeiros Júnior
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 29/06/2011 PT
Relevância na Pesquisa
36.75%
Circulação extracorpórea é um processo no qual o sangue circula externamente ao corpo com o intuito de manter a oxigenação e o fluxo do sangue adequados durante a realização de determinados procedimentos cirúrgicos; para realizá-la é utilizado um conjunto de técnicas e equipamentos cuja função é substituir temporariamente o coração e os pulmões. Contudo, a circulação extracorpórea é percebida pelo organismo como um agente agressor e um dos principais parâmetros relacionados aos danos que ela provoca é a hemólise. O uso de bombas propulsoras é um dos causadores de hemólise em procedimentos envolvendo circulação extracorpórea e um dos principais tipos de bombas propulsoras é a bomba de roletes. A hemólise provocada pelo uso de bomba de roletes é devida principalmente ao grau de oclusão utilizado. Há dois métodos geralmente utilizados para calibração da bomba de roletes: o método de velocidade de queda e o método de calibração dinâmica. Nesse trabalho é proposto um dispositivo para auxiliar o perfusionista a ajustar bombas de roletes por um método menos oclusivo, a calibração dinâmica. O dispositivo é baseado em um microcontrolador PIC 18F4523 e é utilizado em conjunto com transdutores de pressão descartáveis normalmente utilizados em procedimentos cirúrgicos. Foram determinadas as curvas características de três transdutores de pressão na faixa de 0 a 1000 mmHg. Os resultados das calibrações realizadas com o protótipo desenvolvido foram comparados com os resultados obtidos com uma placa de aquisição de dados comercial. Dois...

Efeito da autocalibração volumétrica para PIV tomográfica no campo de velocidade em uma seção de um riser de um leito fluidizado circulante; Volume self-calibration effect for tomographic PIV in velocity fiel in a riser section of a circulating fluidized bed

Rodrigo de Lima Amaral
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 25/04/2013 PT
Relevância na Pesquisa
36.81%
A técnica de Velocimetria por Imagem de Partícula (PIV) é empregada na caracterização do campo de velocidade em diversos tipos de escoamentos. A técnica PIV do tipo tomográfica (Tomographic PIV ou PIV Tomográfica) possibilita a determinação do campo de velocidade do fluido em três dimensões, utilizando partículas que seguem fielmente o fluxo desse fluido. A técnica faz uso de visualizações simultâneas, perspectivas diferentes, das partículas, iluminadas por laser, e sua reconstrução 3D como uma distribuição de intensidade de luz por meio da tomografia óptica para determinação dos vetores velocidades por correlação cruzada 3D. A relação entre a imagem (projeção) e as coordenadas do espaço físico (o objeto) é estabelecida por um procedimento de calibração. Cada câmera registra imagens de um alvo calibração em várias posições de profundidade em todo o volume. A partir dessas imagens o procedimento de calibração retorna uma função de mapeamento. Um procedimento de autocalibração é feito para diminuir o erro da calibração. A autocalibração é uma técnica para a correção a posterior do desalinhamento do sistema de câmeras e pode melhorar significativamente a precisão da reconstrução tomográfica...

Tonometer calibration in Brasília, Brazil

Abrão,Fernanda Pires da Silva; Araújo,Warley Alves; Vieira,Geraldo Magela
Fonte: Conselho Brasileiro de Oftalmologia Publicador: Conselho Brasileiro de Oftalmologia
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/06/2009 EN
Relevância na Pesquisa
36.75%
PURPOSE: To determine calibration errors of Goldmann applanation tonometers in ophthalmic clinics of Brasília, Brazil, and correlate the findings with variables related to tonometers model and utilization. METHODS: Tonometers from ophthalmic clinics in Brasília, Brazil, were checked for calibration errors. A standard Goldmann applanation tonometer checking tool was used to asses the calibration error. Only one trained individual made all verifications, with a masked reading of the results. Data on the model, age, daily use, frequency of calibration checking and the nature of the ophthalmic department - private or public - were collected and correlated with the observed errors. RESULTS: One hundred tonometers were checked for calibration. Forty seven percent (47/100) were out of 1 mmHg range at least at one point checking. Tonometers mounted to slit lamp, with less than 5 years, used in less than 20 patients daily, that had a calibration check on a yearly basis, and those from private office exhibit a lower rate of inaccuracy, but only the first variable was statistically significant. Sixty one percent of tonometers on public hospitals were out of calibration. CONCLUSION: Calibration of tonometers in the capital of Brazil is poor; those from general hospitals are worst...

Improved Criteria for Estimating Calibration Factors for Highway Safety Manual (HSM) Applications

Saha, Dibakar
Fonte: FIU Digital Commons Publicador: FIU Digital Commons
Tipo: Artigo de Revista Científica Formato: application/pdf
Relevância na Pesquisa
36.77%
The Highway Safety Manual (HSM) estimates roadway safety performance based on predictive models that were calibrated using national data. Calibration factors are then used to adjust these predictive models to local conditions for local applications. The HSM recommends that local calibration factors be estimated using 30 to 50 randomly selected sites that experienced at least a total of 100 crashes per year. It also recommends that the factors be updated every two to three years, preferably on an annual basis. However, these recommendations are primarily based on expert opinions rather than data-driven research findings. Furthermore, most agencies do not have data for many of the input variables recommended in the HSM. This dissertation is aimed at determining the best way to meet three major data needs affecting the estimation of calibration factors: (1) the required minimum sample sizes for different roadway facilities, (2) the required frequency for calibration factor updates, and (3) the influential variables affecting calibration factors. In this dissertation, statewide segment and intersection data were first collected for most of the HSM recommended calibration variables using a Google Maps application. In addition, eight years (2005-2012) of traffic and crash data were retrieved from existing databases from the Florida Department of Transportation. With these data...

Testing the impact of calibration on molecular divergence times using a fossil-rich group: the case of Nothofagus (Fagales)

Sauquet, H.; Ho, S.; Gandolfo, M.; Jordan, G.; Wilf, P.; Cantrill, D.; Bayly, M.; Bromham, L.; Brown, G.; Carpenter, R.; Lee, D.; Murphy, D.; Kale Sniderman, J.; Udovicic, F.
Fonte: Taylor & Francis Ltd Publicador: Taylor & Francis Ltd
Tipo: Artigo de Revista Científica
Publicado em //2012 EN
Relevância na Pesquisa
36.77%
Although temporal calibration is widely recognized as critical for obtaining accurate divergence-time estimates using molecular dating methods, few studies have evaluated the variation resulting from different calibration strategies. Depending on the information available, researchers have often used primary calibrations from the fossil record or secondary calibrations from previous molecular dating studies. In analyses of flowering plants, primary calibration data can be obtained from macro- and mesofossils (e.g., leaves, flowers, and fruits) or microfossils (e.g., pollen). Fossil data can vary substantially in accuracy and precision, presenting a difficult choice when selecting appropriate calibrations. Here, we test the impact of eight plausible calibration scenarios for Nothofagus (Nothofagaceae, Fagales), a plant genus with a particularly rich and well-studied fossil record. To do so, we reviewed the phylogenetic placement and geochronology of 38 fossil taxa of Nothofagus and other Fagales, and we identified minimum age constraints for up to 18 nodes of the phylogeny of Fagales. Molecular dating analyses were conducted for each scenario using maximum likelihood (RAxML + r8s) and Bayesian (BEAST) approaches on sequence data from six regions of the chloroplast and nuclear genomes. Using either ingroup or outgroup constraints...

Network-based control, monitoring and calibration of shipboard sensors

Silva, Eusebio Pedro da
Fonte: Monterey, California. Naval Postgraduate School Publicador: Monterey, California. Naval Postgraduate School
Tipo: Tese de Doutorado Formato: xviii, 63 p. : col. ill. ;
Relevância na Pesquisa
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Approved for public release; distribution in unlimited.; The objective of this thesis is to develop a new calibration system for analog and smart digital pressure sensors, operable by only one person, and capable of calibrating local and remote sensors connected via RS232 cables, Bluetooth or an 802.11b wireless LAN. It is proposed that the operator uses a portable calibration standard and a tablet PC to conduct the sensor calibration. In order to handle local sensors directly connected to the tablet PC and remote sensors connected to the tablet PC via a network capable application processor (NCAP), a dual module application is proposed and developed using LabVIEW. The application has a Master Module and a Slave Module. Both modules are able to connect to multiple digital sensors at the same time. The Master Module was designed to run on the operator's tablet PC offering an easy-to-use graphical user interface (GUI) that allows the monitoring or calibration of any connected sensors. The Slave Module was designed to run on any networked PC, including the operator's tablet and an NCAP. A dedicated Virtual Instrument (VI) was designed for an iterative calibration process based on a least squares fitting method. This VI automatically computes the calibration constants that minimize the measurements errors...

An Automated Ultrasound Calibration Framework Incorporating Elevation Beamwidth for Tracked Ultrasound Interventions

Chen, Kuiran
Fonte: Quens University Publicador: Quens University
Tipo: Tese de Doutorado
EN; EN
Relevância na Pesquisa
36.83%
Image-guided surgeries employ advanced imaging and computing technologies to assist the surgeon when direct visualization is inadequate or unavailable. As modern surgeries continue to move toward minimally invasive procedures, tracked ultrasound (US), an emerging technology that uniquely combines US imaging and position tracking, has been increasingly used for intraoperative guidance in surgical interventions. The intrinsic accuracy of a tracked US system is primarily determined by a unique procedure called ``probe calibration", where a spatial registration between the coordinate systems of the transducer (provided by a tracking device affixed to the probe) and the US image plane must be established prior to imaging. Inaccurate system calibration causes misalignments between the US image and the surgical end-effectors, which may directly contribute to treatment failure. The probe calibration quality is further reduced by the "elevation beamwidth" or "slice thickness", a unique feature of the ultrasound beam pattern that gives rise to localization errors and imaging uncertainties. In this thesis, we aim to provide an automated, pure-computation-based, intraoperative calibration solution that also incorporates the slice thickness to improve the calibration accuracy...

SIMULATED AND EXPERIMENTAL KINEMATIC CALIBRATION OF A 4 DEGREES OF FREEDOM PARALLEL MANIPULATOR

Horne, Andrew
Fonte: Quens University Publicador: Quens University
Tipo: Tese de Doutorado
EN; EN
Relevância na Pesquisa
36.81%
This thesis discusses the kinematic calibration of the constraining linkage of a four degrees of freedom parallel manipulator. The manipulator has hybrid actuation of joints and wires, however the wires are not considered in this calibration. Two of the passive joints of the manipulator contain sensing so the calibration of the constraining linkage can be considered. Four kinematic models are developed for the manipulator. For each of these models, an independent set of model parameters are identified through an analysis of the augmented identification Jacobian matrix. Three different methods for formulating the augmented identification Jacobian matrix are explored. For the calibration, an optical tracking system is used to track the end-effector of the manipulator. The procedure to collect the calibration data is explained and the sources of error are considered. To further analyze the sources of error, simulated input data is created and the calibration using the experimental data and the simulated data are compared. In an attempt to improve the calibration, the selection of measured poses to be used for calibration is explored. Several different pose selection criteria have been proposed in the literature and five are evaluated in this work. The pose selection criteria were applied to the experimental manipulator and also a simulated two degrees of freedom manipulator. It is found that the pose selection criteria have a large impact when few poses are used; however the best results occur when a large number of poses are used for the calibration. An experimental calibration is carried out for the manipulator. Using the joint encoders and the kinematic model...

Calibration de systèmes de caméras et projecteurs dans des applications de création multimédia

Bélanger, Lucie
Fonte: Université de Montréal Publicador: Université de Montréal
Tipo: Thèse ou Mémoire numérique / Electronic Thesis or Dissertation
FR
Relevância na Pesquisa
36.86%
Ce mémoire s'intéresse à la vision par ordinateur appliquée à des projets d'art technologique. Le sujet traité est la calibration de systèmes de caméras et de projecteurs dans des applications de suivi et de reconstruction 3D en arts visuels et en art performatif. Le mémoire s'articule autour de deux collaborations avec les artistes québécois Daniel Danis et Nicolas Reeves. La géométrie projective et les méthodes de calibration classiques telles que la calibration planaire et la calibration par géométrie épipolaire sont présentées pour introduire les techniques utilisées dans ces deux projets. La collaboration avec Nicolas Reeves consiste à calibrer un système caméra-projecteur sur tête robotisée pour projeter des vidéos en temps réel sur des écrans cubiques mobiles. En plus d'appliquer des méthodes de calibration classiques, nous proposons une nouvelle technique de calibration de la pose d'une caméra sur tête robotisée. Cette technique utilise des plans elliptiques générés par l'observation d'un seul point dans le monde pour déterminer la pose de la caméra par rapport au centre de rotation de la tête robotisée. Le projet avec le metteur en scène Daniel Danis aborde les techniques de calibration de systèmes multi-caméras. Pour son projet de théâtre...

Evaluation of Centrally Located Sources in Coincidence Timing Calibration for Time-of-Flight PET

Wargo, Richard Ryan
Fonte: Universidade Duke Publicador: Universidade Duke
Tipo: Tese de Doutorado
Publicado em //2012
Relevância na Pesquisa
36.78%

Coincidence Timing Calibration (CTC) is an essential part of ensuring proper PET scanner function. The purpose of CTC is to account for timing differences in detector modules. The importance and precision in which this calibration needs to work is even more stringent for Time-of-Flight (TOF) PET. In this work, we looked to investigate the CTC process by which the TOF capable GE PET/CT Discovery-690 (D690) operates. Currently, it uses a 68Ge rotating pin source (RPS) to perform the calibration. The purpose of this work was to investigate the use of a centrally located source to perform the calibration. The timing resolution of the D690 was determined and used as a metric to evaluate both methods.

Two cylindrical 18F filled phantoms of 7.5 and 10 cm diameter were used to perform the CTC. The RPS and system table motion had to be disabled in order to use the centrally located sources in the CTC. All CTCs started with the default calibration file in place. Iterations of the CTC were performed until convergence of the calibration was observed on the review screen. Even after convergence, more iterations were performed for further analysis. At the end of the CTC with the centrally located sources, a follow-up iteration with the RPS was performed to see what adjustments would be made. Next...

Landsat TM and ETM+ thermal band calibration

Barsi, Julia; Schott, John; Palluconi, Frank; Helder, Dennis; Markham, Brian; Chander, Gyanesh; O'Donnell, Erin
Fonte: Canadian Remote Sensing Society Publicador: Canadian Remote Sensing Society
Tipo: Artigo de Revista Científica
EN_US
Relevância na Pesquisa
36.77%
Landsat-5 has been imaging the Earth since March 1984, and Landsat-7 was added to the series of Landsat instruments in April 1999. The Landsat Project Science Office and the Landsat-7 Image Assessment System have been monitoring the on-board calibration of Landsat-7 since launch. Additionally, two separate university teams have been evaluating the on-board thermal calibration of Landsat-7 through ground-based measurements since launch. Although not monitored as closely over its lifetime, a new effort is currently being made to validate the calibration of Landsat-5. Two university teams are beginning to collect ground truth under Landsat-5, along with using other vicarious calibration methods to go back into the archive to validate the history of the calibration of Landsat-5. This paper considers the calibration efforts for the thermal band, band 6, of both the Landsat-5 and Landsat-7 instruments. Though stable since launch, Landsat-7 had an initial calibration error of about 3 K, and changes were made to correct for this beginning 1 October 2000 for data processed with the National Landsat Archive Production System (NLAPS) and beginning 20 December 2000 for data processed with the Landsat Product Generation System (LPGS). Recent results from Landsat-5 vicarious calibration efforts show an offset of –0.7 K over the lifetime of the instrument. This suggests that historical calibration efforts may have been detecting errors in processing systems rather than changes in the instrument. A correction to the Landsat-5 processing has not yet been implemented but will be in the near future.; Appears in the specialized issue...

Calibration history of Landsat thermal data

O'Donnell, Erin; Schott, John; Raqueno, Nina
Fonte: Institute of Electrical and Electronics Engineers (IEEE) Publicador: Institute of Electrical and Electronics Engineers (IEEE)
Tipo: Artigo de Revista Científica
EN_US
Relevância na Pesquisa
36.77%
This research studied the calibration of the thermal band (band 6) of the Landsat 5 satellite. The Landsat system of instruments are land observing satellites intended for long-term studies of the earth. Landsat 5 has been in use since 1984 and is still active. Until recently there has not been a rigorous study of the performance of its thermal band. The users of this thermal data had been using the data without knowing the status of the instrument. Over the years the instrument has had the potential to drift in calibration, especially since the instrument has surpassed its expected lifetime. In fact, when Landsat 7 was launched in 1999 there had not been a systematic check of thermal calibration of Landsat 5 since shortly after its launch. Taking advantage of the fact that the two sensors, Landsat 5 and 7, were simultaneously operational, a cross-calibration was possible. As Landsat 7 maneuvered into its orbit, it passed under Landsat 5's path resulting in both sensors having common spatial and temporal coverage. Using this common data the calibration of Landsat 5 was shown to be within measurement error. A historical calibration was also performed on Landsat 5's thermal band. This was done using various Landsat 5 images of the Great Lakes from when it was launched in 1984 to 1999. Early spring images of the Great Lakes were used because of the thermal bar phenomena that occurs. The thermal bar creates a boundary of known temperature with-in the center of the lake. This known temperature boundary is used as a calibration reference. This historical calibration revealed that Landsat 5's thermal band has been operating nominally...

Historic thermal calibration of landsat 5 TM through an improved physics based approach

Padula, Francis P.
Fonte: Rochester Instituto de Tecnologia Publicador: Rochester Instituto de Tecnologia
Tipo: Tese de Doutorado
EN_US
Relevância na Pesquisa
36.81%
This investigation is motivated by the current need for a detailed post launch calibration of the Thematic Mapper (TM) thermal band (Band 6), aboard NASA’s Landsat 5 spacecraft. The historical calibration spans the period from 1984 to 2007. It is through fusion of environmental data sources (i.e. buoy observations, surface observations, and radiosonde observations) that a vicarious calibration approach will be implemented to construct the complete calibration record of the Landsat 5 TM thermal band. The vicarious calibration process takes advantage of the long standing National Data Buoy Center (NDBC) moored buoy fleet to acquire historic ground truth measurements needed over the lifetime of Landsat 5. These measurements are propagated to the sensor through the use of physics based models to establish a predicted at sensor radiance. Through comparison of the predicted at sensor radiance and the actual sensor observed radiance, a calibration metric is established. Results indicate the Landsat 5 TM thermal band, originally planned for a 3 year mission, has fluctuated only slightly ( 1 K) over the 24+ years in orbit. The calibration curve developed in this study is consistent with previous results from campaigns preformed in 1985 and post 1999. The data indicated that the sensor exhibited a clear gain issue (i.e. over estimates low radiance targets and under estimates high radiance targets) found to be approximately consistent over time. Additionally...

Refinement of the method for using pseudo-invariant sites for long term calibration trending of Landsat reflective bands

Anderson, Clifton R.
Fonte: Rochester Instituto de Tecnologia Publicador: Rochester Instituto de Tecnologia
Tipo: Dissertação
EN_US
Relevância na Pesquisa
36.8%
The long term calibration history of the Landsat 5 TM instrument has recently been defined using a time series of desert sites in Northern Africa. This correction is based on the assumption that the atmosphere is invariant and the reflectance of each site is approximately constant and Lambertian over time. As a result, the top of the atmosphere reflection is assumed constant when corrected for variations in the solar elevation angle and earth-sun distance. While this is true to first order and is the basis for all current temporal calibration, there are multiple known sources of residual error in the data. A methodology is presented for reducing the variation in pseudo-invariant site trending data based on correction for the BRDF. This work establishes a means to use DIRSIG to model the L5 calibration site. It combines a digital elevation map and desert atmosphere with a surface BRDF to reduce the residual errors in the calibration data. A set of Landsat 7 ETM+ calibration days is utilized to optimize the surface reflectance properties used in DIRSIG. These optimized parameters are then used to model the L5 TM calibration days. The results of the DIRSIG modeling are compared to the solar elevation angle and time of year trends of the original data and analyzed for their effectiveness at describing and reducing the residual errors. A major goal of this effort is to understand the contribution that BRDFs make to the current calibration errors and to develop methods that are robust enough to be applicable to a wider range of sites to enable extension of the methodology to earlier data sets (e.g. Landsat MSS). Additionally...

A definitive calibration record for the Landsat-5 thematic mapper anchored to the Landsat-7 radiometric scale

Teillet, Philippe; Helder, Dennis; Ruggles, Timothy; Landry, Richard; Ahern, Frank; Higgs, Nicholas; Barsi, Julia; Chander, Gyanesh; Markham, Brian; Barker, John; Thome, Kurtis; Schott, John; Palluconi, Frank
Fonte: Canadian Remote Sensing Society: Canadian Aeronautics and Space Institute Publicador: Canadian Remote Sensing Society: Canadian Aeronautics and Space Institute
Tipo: Artigo de Revista Científica
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A coordinated effort on the part of several agencies has led to the specification of a definitive radiometric calibration record for the Landsat-5 thematic mapper (TM) for its lifetime since launch in 1984. The time-dependent calibration record for Landsat-5 TM has been placed on the same radiometric scale as the Landsat-7 enhanced thematic mapper plus (ETM+). It has been implemented in the National Landsat Archive Production Systems (NLAPS) in use in North America. This paper documents the results of this collaborative effort and the specifications for the related calibration processing algorithms. The specifications include (i) anchoring of the Landsat-5 TM calibration record to the Landsat-7 ETM+ absolute radiometric calibration, (ii) new time-dependent calibration processing equations and procedures applicable to raw Landsat-5 TM data, and (iii) algorithms for recalibration computations applicable to some of the existing processed datasets in the North American context. The cross-calibration between Landsat-5 TM and Landsat-7 ETM+ was achieved using image pairs from the tandem-orbit configuration period that was programmed early in the Landsat-7 mission. The time-dependent calibration for Landsat-5 TM is based on a detailed trend analysis of data from the on-board internal calibrator. The new lifetime radiometric calibration record for Landsat-5 will overcome problems with earlier product generation owing to inadequate maintenance and documentation of the calibration over time and will facilitate the quantitative examination of a continuous...

Historic thermal calibration of Landsat 4 TM through an improved physics based approach

Miller, Jonathan
Fonte: Rochester Instituto de Tecnologia Publicador: Rochester Instituto de Tecnologia
Tipo: Tese de Doutorado
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36.78%
This work is intended to establish the calibration of the Thematic Mapper (TM) sensor, thermal band (band 6) aboard the Landsat 4 Spacecraft. Due to multiple organizations having operational control of the spacecraft and a lack of historical calibration data, a physics based approach will be used to calibrate the thermal data recorded over water during the operational lifetime of the spacecraft, which spanned 1983-1993. Using historical data from weather station observations, Radiosonde instruments, and moored weather buoys owned and operated by the National Data Buoy Center (NDBC), a ground truth comparison can be calculated and propagated through the atmosphere using a physics based model. The ground truth measurements are then compared to archived Landsat 4 data to determine how well the instrument is calibrated. This comparison over many data points allows construction of an overall calibration curve for the Landsat 4 data over the lifetime of the spacecraft. In addition to calibrating the Landsat 4 TM, this research will also include investigation into a possible transition period of negative to positive bias on the Landsat 5 TM, somewhere in the 1996-1999 timeframe. The same technique will be used in both calibration attempts. Results indicate that the Landsat 4 data was well calibrated in the timeframe before storage (1983-1984)...