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Gabor filter parameter optimization for multi-textured images : a case study on water body extraction from satellite imagery.Pillay, Maldean. January 2012 (has links)
The analysis and identification of texture is a key area in image processing and computer
vision. One of the most prominent texture analysis algorithms is the Gabor Filter.
These filters are used by convolving an image with a family of self similar filters or
wavelets through the selection of a suitable number of scales and orientations, which
are responsible for aiding in the identification of textures of differing coarseness and
directions respectively.
While extensively used in a variety of applications, including, biometrics such as iris and
facial recognition, their effectiveness depend largely on the manual selection of different
parameters values, i.e. the centre frequency, the number of scales and orientations, and
the standard deviations. Previous studies have been conducted on how to determine
optimal values. However the results are sometimes inconsistent and even contradictory.
Furthermore, the selection of the mask size and tile size used in the convolution process
has received little attention, presumably since they are image set dependent.
This research attempts to verify specific claims made in previous studies about the
influence of the number of scales and orientations, but also to investigate the variation of
the filter mask size and tile size for water body extraction from satellite imagery. Optical
satellite imagery may contain texture samples that are conceptually the same (belong
to the same class), but are structurally different or differ due to changes in illumination,
i.e. a texture may appear completely different when the intensity or position of a light
source changes.
A systematic testing of the effects of varying the parameter values on optical satellite
imagery is conducted. Experiments are designed to verify claims made about the influence of varying the scales and orientations within predetermined ranges, but also to
show the considerable changes in classification accuracy when varying the filter mask
and tile size. Heuristic techniques such as Genetic Algorithms (GA) can be used to find
optimum solutions in application domains where an enumeration approach is not feasible.
Hence, the effectiveness of a GA to automate the process of determining optimum
Gabor filter parameter values for a given image dataset is also investigated.
The results of the research can be used to facilitate the selection of Gabor filter parameters
for applications that involve multi-textured image segmentation or classification,
and specifically to guide the selection of appropriate filter mask and tile sizes for automated
analysis of satellite imagery. / Thesis (M.Sc.)-University of KwaZulu-Natal, Durban, 2012.
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Distributed real-time processing using GNU/Linux/libré software and COTS hardwareVan Schalkwyk, Dirko 03 1900 (has links)
Thesis (MScIng)--Stellenbosch University, 2004. / ENGLISH ABSTRACT: This dissertation's research aims at studying the viability of using both low cost
consumer Commodity Off The Self (COTS) PCs and libn~software in implementing a
distributed real-time system modeled on a real-world engineering problem.
Debugging and developing a modular satellite system is both time consuming
and complex, to this end the SUNSATteam has envisioned the Interactive Test System
that would be a dual mode simulator/monitoring system. It is this system that requires
a real-time back-end and is used as a real world problem model to implement.
The implementation was accomplished by researching the available parallel processing
software and real-time extensions to GNU/Linux and choosing the appropriate
solutions based on the needs of the model. A monitoring system was also implemented,
for system verification, using freely available system monitoring utilities.
The model was successfully implemented and verified with a global synchronization
of < 10ms. It was shown that GNU/Linux and libn~ software is both mature
enough and appropriate in solving a real world distributed real-time problem. / AFRIKAANSE OPSOMMING: Die tesis se navorsing is daarop gemik om die toepaslikheid van beide lae koste verbruikers
Komoduteits Van Die Rak (KVDR)persoonlike rekenaars en vemiet sagteware
in die implementasie van verspreide intydse stelsels te ondersoek aan die hand van die
oplossing van 'n gemodelleerde ingenieurs probleem.
Die ontfouting en ontwikkeling van 'n modulere satelliet is beide tyd rowend en
kompleks, om hierdie te vergemaklik het die SUNSAT span die Interaktiewe Toets
Stelsel gekonseptualiseer, wat in wese'n dubbel modus simulator/moniteerings stelsel
sou wees. Dit is hierdie stelsel wat 'n verspreide intydse onderstel benodig en dien as
die regte wereld probleem model om op te los.
Die implementasie is bereik deur die beskikbare verspreide verwerkings sagteware
en intydse uitbreidings vir GNU/Linux te ondersoek en die toepaslike opsies te
kies gegrond op die behoeftes van die model. 'n Moniteerings stelsel is ook geimplimenteer,
met behulp van libn~sagteware, vir stelsel verifikasie.
Die model was suksesvol geimplimenteer en geverifieer met 'n globale sinkronisasie
van < 10ms. Daar is getoon dat GNU/Linux en libn~sagteware beide volwaardig en
geskik is vir die oplossing van regte wereld verspreide intydse probleme.
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The development of Sun and Nadir sensors for a solar sail CubeSatLoubser, Hanco Evert 03 1900 (has links)
Thesis (MScEng (Electrical and Electronic Engineering))--University of Stellenbosch, 2011. / ENGLISH ABSTRACT: This thesis describes the development of attitude sensors required for the Attitude Determination and
Control System (ADCS) for a Cubesat. The aim is to find the most suitable sensors for use on a small picosatellite
by implementing miniaturised sensors with available commercial-off-the-shelf (COTS) technology.
Specifically, the algorithms, hardware prototypes, software and filters required to create accurate sensors
to determine the 3-axis orientation of a CubeSat are discussed. / AFRIKAANSE OPSOMMING: Hierdie tesis beskryf die ontwikkeling van oriëntasiesensors wat benodig word vir die oriëntasiebepaling
en -beheerstelsel (Engels: ADCS) van ’n CubeSat. Die doelwit is om sensors te vind wat die geskikste is om
in ’n klein picosatelliet te gebruik, deur miniatuursensors met kommersiële maklik verkrygbare tegnologie
(Engels: COTS technology) te implementeer. Daar word in die bespreking veral aandag geskenk aan die
algoritmes, hardewareprototipes, programmatuur en filters wat benodig word om akkurate sensors te
skep wat op hul beurt 3-as oriëntasie van die CubeSat kan bepaal.
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Orbital lifetime predictions of Low Earth Orbit satellites and the effect of a DeOrbitSailAfful, Michael Andoh 12 1900 (has links)
Thesis (MEng)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: Throughout its lifetime in space, a spacecraft is exposed to risk of collision with orbital
debris or operational satellites. This risk is especially high within the Low Earth Orbit
(LEO) region where the highest density of space debris is accumulated.
This study investigates orbital decay of some LEO micro-satellites and accelerating orbit
decay by using a deorbitsail. The Semi-Analytical Liu Theory (SALT) and the Satellite
Toolkit was employed to determine the mean elements and expressions for the time rates
of change. Test cases of observed decayed satellites (Iridium-85 and Starshine-1) are used
to evaluate the predicted theory. Results for the test cases indicated that the theory tted
observational data well within acceptable limits.
Orbit decay progress of the SUNSAT micro-satellite was analysed using relevant orbital
parameters derived from historic Two Line Element (TLE) sets and comparing with decay
and lifetime prediction models. The study also explored the deorbit date and time for a
1U CubeSat (ZACUBE-01).
A proposed orbital debris solution or technology known as deorbitsail was also investigated
to gain insight in sail technology to reduce the orbit life of spacecraft with regards to de-
orbiting using aerodynamic drag. The deorbitsail technique signi cantly increases the
e ective cross-sectional area of a satellite, subsequently increasing atmospheric drag and
accelerating orbit decay. The concept proposed in this work introduces a very useful
technique of orbit decay as well as deorbiting of spacecraft. / AFRIKAANSE OPSOMMING: Gedurende sy leeftyd in die ruimte word 'n ruimtetuig blootgestel aan die risiko van 'n
botsing met ruimterommel of met funksionele satelliete. Hierdie risiko is veral hoog in die
lae-aardbaan gebied waar die hoogste digtheid ruimterommel voorkom.
Hierdie studie ondersoek die wentelbaanverval van sommige Lae-aardbaan mikrosatelliete
asook die versnelde baanverval wanneer van 'n deorbitaal meganisme gebruik gemaak word.
Die Semi-Analitiese Liu Teorie en die Satellite Toolkit sagtewarepakket is gebruik om die
gemiddelde baan-elemente en uitdrukkings vir hul tyd-afhanlike tempo van verandering
te bepaal. Toetsgevalle van waargenome vervalde satelliete (Iridium-85 en Starshine-1) is
gebruik om die verloop van die voorspelde teoretiese verval te evalueer. Resultate vir die
toetsgevalle toon dat die teorie binne aanvaarbare perke met die waarnemings ooreenstem.
Die verloop van die SUNSAT mikrosatelliet se wentelbaanverval is ook ontleed deur gebruik
te maak van historiese Tweelyn Elemente datastelle en dit te vergelyk met voorspelde baan-
elemente. Die studie het ook ondersoek ingestel na die voorspelde baan-verbyval van 'n
1-eenheid cubesat (ZACUBE-01).
Die impak op wentelbaanverval deur 'n voorgestelde oplossing vir die beperking van
ruimterommel, 'n deorbitaalseil, is ook ondersoek. So seil verkort 'n satelliet se ruimte-
leeftyd deur sy e ektiewe deursnee-area te vergroot en dan van verhoogde atmosferiese
sleur en sonstralingsdruk gebruik te maak om die vervalproses te versnel. Hierdie voorgestelde
konsep is 'n moontlike nuttige tegniek vir versnelde baanverval en beheerde deorbitalering
van ruimtetuie om ruimterommel te verminder.
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Development of a radiation resistant communication node for satellite sub-systemsThesnaar, Emile Jacobus 04 1900 (has links)
Thesis (MEng)--Stellenbosch University, 2014. / ENGLISH ABSTRACT: Within a complex electronic system, sub-system communication forms the backbone of the
functionality of any satellite. It allows multiple processors to run simultaneously and data
to be shared amongst them. Without it, a single processor would have to control the entire
satellite. Not only would such a design then be overly complicated, but the processor would
also not have sufficient capacity to service all the components efficiently.
Furthermore the detrimental effects that radiation have on integrated circuits are well documented
and can be anything from a single bit flip to a complete integrated circuit failure.
If not repaired, a failure on a sub-system communication bus could lead to the loss of the
entire satellite.
Die goal is to create more radiation resistant Controller-Area-Network (CAN) node. Since a
full triple modular redundant design will have a large footprint and high power consumption,
a combination of techniques will be applied and tested. The goal is to achieve improved
footprint utilisation over triple modular redundancy, while still maintaining good resistance
to Single Event Upsets (SEU).
By applying simulation, it was sufficiently proven that the implementation of the individual
techniques used functioned according to expectations. These techniques included error detection
and correction using Hamming Codes, single event transient filter and triple modular
redundancy. Having applied these mitigation techniques, the footprint of the CAN controller
increased by only 116%. Simulation showed that the Error Detection and Correction and
Triple Modular Redundancy worked effectively with the CAN controller, and that the CAN
controller could function as originally intended. Using radiation testing, the design proved
to be more resistant to SEUs than the unmitigated CAN controller.
It was thus shown that through using a combination of mitigation techniques, it is possible
to develop an optimal design with a high level of resistance against Single Event Upsets,
utilizing a smaller footprint than implementing Triple Modular Redundancy. / AFRIKAANSE OPSOMMING: Sub-stelsel kommunikasie vorm die basis van die funksionaliteit in ’n komplekse elektroniese
stelsel soos ’n satelliet. Dit skep die vermoë om veelvoudige verwerkers gelyktydig te laat
funksioneer en inligting tussen hulle te deel. Sonder sub-stelsel kommunikasie, sal ’n enkele
verwerker die hele sateliet moet beheer. Dit sal nie net die hele ontwerp oorkompliseer nie,
maar die verwerker sal ook nie genoeg kapisteit hê om al die komponente effektief te diens
nie.
Die newe-effekte van bestraling op geïntegreerde stroombane is goed gedokumenteer en kan
wissel van ’n enkele omgekeerde bis, tot die vernietiging van die geïntegreerde stroombaan.
Indien die fout in die kommunikasiestelsel nie herstel word nie, kan dit lei tot die verlies van
die hele sateliet.
Die doel is om ’n meer bestraling bestande Controller-Area-Network (CAN) nodus te skep.
Aangesien ’n volle drie-dubbele-modulêre-oortollige ontwerp ’n baie groot area beslaan en
hoë krag verbruik het, gaan ’n kombinasie van versagting tegnieke toegepas en ge-evalueer
word. Die doel is om beter area benutting as die drie-dubble-modulêre-oortollige ontwerp
te kry, terwyl ’n goeie weerstand teen foute behoue bly.
Deur middel van simulasies is voldoende bewyse gelewer dat die implimentasie van die individuele
versagting tegnieke soos verwag funktioneer. Hierdie tegnieke sluit in, fout opsporing
en regstelling deur middel van Hamming kodes, enkele geval oorgangs verskynsel filter asook
drie-dubbele-modulêre-oortollige ontwerp. Nadat versagting meganismes toegepas is, het die
area verbruik van die CAN beheerder toegeneem met slegs 116%. Simulasies het bewys dat
Fout Opsporing en Regstelling en Drie-Dubbele-Modulêre-Oortollige ontwerp tegnieke binne
die CAN beheerder korrek funktioneer, terwyl die CAN beheerder self funktioneer soos dit
oorspronklik gefunksioneer het. Deur middel van bestralingstoetse, is dit bewys dat die
ontwerp meer bestand is teen foute geïnduseer deur bestraling as die onbeskermde CAN
beheerder.
Dit is dus bewys dat deur gebruik te maak van verskeie versagting tegnieke dit moontlik is
om ’n optimale ontwerp te implimenteer, met ’n hoë weerstand teen foute, maar met ’n laer
area verbruik as die van ’n Drie-dubbele-Modulêre-Oortollige ontwerp.
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The use of high-resolution satellite imagery in forest inventory : a case of Hans Kanyinga Community Forest - NamibiaKamwi, Jonathan Mutau 12 1900 (has links)
Thesis (MSc (Forest and Wood Science))—University of Stellenbosch, 2007. / The present study investigated double sampling with regression estimators as a quest for efficiency and effectiveness in forest inventory in Namibian woodlands. Auxiliary data used were obtained from Standard QuickBird satellite scenes (phase 1) for Hans Kanyinga Community Forest from October and November 2004 covering an area of 12,107 hectares, amplified with terrestric data (phase 2) of 2002. The relationships between auxiliary and terrestric variables are described and prediction models were constructed. According to the results of the stepwise procedure with the Mallow’s Cp statistic as the selection criteria, photogrammetric stand density and a combination of the photogrammetric crown area with photogrammetric stand density were the best candidates for predicting the stand volume. The resulting volume model explains 56% of the variation. Photogrammetric stand density was found to be highly correlated to the terrestric stand density with the resulting model explaining 81% of the variation. Photogrammetric crown diameter was found to be correlated with the diameter at breast height measured from the plots which were assessed for spatial tree positions, which enabled the derivation of the diameter distribution. The diameter distribution model explains 43% of the variation. In addition, the actual tree positions were determined using the GPS and surveying techniques (polar positions) involving distance and bearings. GPS tree positions showed a considerable shift of up to 8.67 m. However, only the distance measurements of tress from the plot centre using the infield surveying methods were more reliable. Nevertheless, the influences of the tree positional errors are not of high concern for temporary based sample plots which are normally used in Namibian forest inventories. A reduction in inventory cost was found to be 24% i.e. N$25.79 to N$19.67 per hectare. The results of this study are valid for Kavango region or any other region with similar set of physical and climatic conditions, but caution must be exercised in implementing these results elsewhere under different physical and environmental conditions.
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An investigation into the feasibility of forest inventory by means of stereo satellite imagery employing digital photogrammetry technologyVogt, Holger K. H January 2000 (has links)
Thesis (MSc)--Stellenbosch University, 2000. / ENGLISH ABSTRACT: The aim of the study was to extract elevation information (such as tree height) from
stereo satellite imagery (IRS-I C), to scrutinise the performance of the DTM (Digital
Terrain Model) tools as provided by the LH (LeicalHelava) Systems' softcopy
system, and subsequently to perform a feasibility study on the application of a
practically viable forest inventory design.
A softcopy photogrammetry workstation (LH Systems DPW 770), IRS-I C stereo
panchromatic satellite imagery, and digital aerial photography at a scale of 1:30000
(scanned at 15 micrometers) was used. The study was conducted over various sites in
the Sabie area (province of Mpumalanga) in South Africa, where extensive man made
forests with pine and eucalypts are to be found. The extraction of stand parameters
such as tree height was performed manually, semi-automatically, and automatically.
In addition, the compartment area was determined using a GIS tool. The Digital
Surface Models (DSM), representing the canopy structure of the stands, was extracted
from the IRS-I C imagery and validated through a comparison of the resulting
contours with the corresponding contours generated by aerial photogrammetric
methods.
Due to the coarse spatial resolution of the IRS-IC imagery (5m) and the suboptimal
BIH (BaselHeight) ratio (0.57), only objects featuring a height exceeding 20m could
be manually measured with confidence. Furthermore, only the edges of the
compartments proved to be suitable for the determination of tree heights (i.e. with a
sufficiently large parallax difference and image contrast).
The manual determination of tree heights in the IRS-I C imagery yielded accuracies of
about 95% compared to the height values of the aerial photographs and the ground
data. The application of image enhancement techniques had severe effects on the
accuracy of the IRS-IC stereo model, resulting in deviations of about -57m from the
'true' value. It was observed that image matching was only a problem where features changed their appearance (e.g. clearfelled or burnt areas) during the acquisition period
of the stereo pair of the satellite imagery.
LH Systems' Adaptive Automatic Terrain Extraction (AATE) tool performed very
well for the creation of digital terrain and surface models when using digital aerial
photography with a high scanning rate. In contrast, the automatic creation of canopy
surface models from various forest compartments did not yield any useful results
when applied to IRS-l C imagery. AATE could not model the canopy structure
properly. The coarse spatial resolution of the satellite imagery in conjunction with the
sparse post spacing (20m) and matching errors are most likely to be responsible for
this poor performance.
Two-phase sampling and the Hugershoff method were chosen for automatically
derived height values to be evaluated for possible application in forest inventory.
Unfortunately, neither for the determination of the regression estimator for the first
method, nor for the calculation of timber volume after application of the Hugershoff
method could any useful result be obtained. This is mostly due to the fact that image
matching errors and blunders (resulting in tree heights of -885m) were not properly
accounted for in the terrain extraction software. However, the outcomes for the
manual measurement of tree heights performed on the satellite imagery show that
under optimal conditions accuracies can be achieved similar to those for the height
determination in small scale aerial photographs, but at lower cost. The obtained height
values can then be used for the calculation of timber volume according to Eichhorn's
law.
Keywords: AATE, blunders, digital photogrammetry, DPW770, forest inventory,
Hugershoff IRS-l C, matching error, remote sensing, satellite
imagery, two-phase sampling / AFRIKAANSE OPSOMMING: N GANGBAARHEIDSTIIDIE VIR BOSINVENTARIS MET BEHULP VAN
STEREO SATELLIETBEELDE MET GEBRUIK VAN SAGTEKOPIE
FOTOGRAMMETRIESETEGNOLOGIE: Die doel van hierdie studie was om elevasie inligting (soos boomhoogtes) uit stereo
satellietbeelde (IRS-I C) te ontrek, en die DTM (Digitale Terrein Modelle) funksies van
die LH Systems se sagtekopie sisteem te evalueer en 'n ondersoek in te stel na praktiese
toepassing van die tegnologie in bosvoorraadopname.
'n Sagtekopie fotogrammetriese werkstasie (LH Systems DPW 770), IRS-I C stereo
panchromatiese satellietwaarneming en digitale lugfotografie is gebruik. Die studie is
uitgevoer oor verskeie areas in die Sabie omgewing (Mpumalanga, Suid-Afrika), waar
daar ekstensiewe mensgemaakte woude voorkom met denne en Eucalyptus soorte. Die
ekstraksie van opstandparameters soos boomhoogte is uitgevoer met die hand, as ook met
semi-outomatiese en outomatiese metodes. Die digitale oppervlakmodelle (wat die
kroondakstrukture van die opstande voorstel) was vanaf die IRS-I C beelde onttrek en
gevalideer deur vergelyking van die resulterende kontoere met die korresponderende
kontoere wat deur lugfotogrammetriese metodes gegenereer is. As gevolg van die
growwe ruimtelike resolusie van die IRS-IC waarneming (Sm) en die suboptimale BIH
verhouding (0.57) kan slegs voorwerpe met 'n hoogte van meer as 20m met vertroue met
die hand gemeet word. Slegs die rande van die vakke is bruikbaar vir die berekening van
boomhoogtes (d.w. s. met 'n voldoende paralaksverskil en 'n sterk beeldkontras ).
Boomhoogtes wat met die hand bepaal is vanaf IRS-I C beelde is 95% akkuraat in
vergelyking met die hoogtewaardes verkry vanaf die lugfoto's en die veldmetings. Die
toepassing van beeldverbeteringstegnieke het duidelike invloede op die akkuraatheid van
die IRS-IC stereomodel met afwykings van ongeveer -57m vanaf die "werklike"
waardes. Daar is ook waargeneem dat beeldooreenstemming slegs 'n probleem is waar
terreinvorme se voorkoms verander het (weens afkappings of brande) gedurende die
verkrygingsperiode waarin die stereo paar van die satellietbeelde verkry is. LH Systems se Aanpassende Outomatiese Terrein Onttrekkings (Adaptive Automatic
Terrain Extraction - AATE) instrument het goed gevaar tydens die gebruik van digitale
lugfotografie met Inhoë skanderingstempo.
In kontras hiermee het die outomatiese skepping van kroondakoppervlakmodelle van
verskeie plantasievakke geen nuttige resultate gelewer wanneer dit op IRS-I C beelde
toegepas is nie. Die growwe ruimtelike resolusie van die satellietbeelde tesame met die
wye paalspasïering (20m) en passingsfoute is waarskynlik vir hierdie swak resultate
verantwoordelik.
Twee-fase proefueming en die Hugershoff metode was gebruik vir die bepaling van
outomaties afgeleide hoogtewaardes vir evaluering van moonlike toepassing in
bosvoorraadopnames. Geen bruikbare resultate kon verkry word vir die vasstelling van
die regressieskatter vir die eersgenoemde metode of vir die berekening van die
houtvolume volgens die Hugershoff metode nie. Dit is meestal as gevolg van beeld--
ooreenkomsfoute en flaters, (wat tot boomhoogtes van -885m gelei het) wat nie
voldoende in ag geneem word in die terreinekstraksie sagteware nie. Die resultate vir die
handgemete ('manual') boomhoogtebepaling wat uitgevoer is op die satellietbeelde (op
die sagtekopie werkstasie DPW 770), toon dat akkuraathede soortgelyk aan daardie vir
hoogte bepaal op klein-skaal lugfotos onder optimale toestande verkry kan word, maar
goedkoper. Die hoogtewaardes wat verkry is kan gebruik word vir die berekening van
houtvolume volgens die wet van Eichhorn.
Sleutelwoorde: AATE, afstandswaarneming, bosvoorraadopnames, digitale
fotogrammetrie, DPW770, flaters, Hugershoff, IRS-! C, satellietbeelde,
twee-fase proefueming
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Posicionamento relativo em tempo real e pós-processado utilizando microrreceptor GNSS usado em smartphone / Relative positioning in real-time and post-processed using GNSS micro receiver used in smartphoneOliveira, Gabriel Diniz de 22 July 2014 (has links)
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Previous issue date: 2014-07-22 / Over time has increased the need for low cost positioning of the populatio, and for this reason the demand for navigation devices has grown considerably in all levels of users of these devices, the population in general has greater access to smartphones because of its many features. Smartphones using micro GNSS receiver has a main component of positioning, where the pseudorange is its basic observable. The data sources for GPS corrections are increasingly available to the community through institutions as the IBGE with the Brazilian Network for Continuous Monitoring (RBMC). Thus, there is a greater possibility of improvement in accuracy of positioning these devices with the post- processed relative positioning and even in real time. With these possibilities and needs, this study aims the establishment of methodology that improves the accuracy in the positioning devices using micro GNSS receiver with a recursive least squares estimation with the Kalman gain matrix applied in relative positioning static by double difference of pseudorange in short baselines. To verify the effectiveness of this methodology is used SiRFstar IV micro receiver data which receives data only in L1 frequency GPS constellation. Was used reference RBMC stations to process these data. With tracking 15 minutes in known points had a mean deviation in the horizontal component of the plane coordinates 29 cm for post-processing and 98 cm for the real time processing, and, for the single point positioning average deviation was 6 meters. With this, it was concluded that the use of static methods for processing on recursive least squares estimation improves the accuracy of positioning significantly, where mobile devices that were previously given only to navigation may also be used for mapping. / Com o passar do tempo aumentou a necessidade da população em posicionamento a baixo custo, e por este motivo a procura por aparelhos de navegação tem crescido consideravelmente em todos os níveis de usuários. Destes dispositivos, a população no geral tem maior acesso aos smartphones devido a suas diversas funcionalidades. Os smartphones utilizam de microrreceptor GNSS como principal componente de posicionamento, sendo que sua observável básica é a pseudodistância derivada do código C/A. As fontes de dados para correções GPS estão cada vez mais disponíveis para a comunidade por meio de instituições como o IBGE com a Rede Brasileira de Monitoramento Continuo dos Sistemas GNSS (RBMC). Com isso, tem-se uma maior possibilidade de melhorias na acurácia do posicionamento destes dispositivos com o posicionamento relativo pós-processado e até mesmo em tempo real. Com estas possibilidades e necessidades, este trabalho tem como objetivo o estabelecimento de metodologia que melhore a acurácia no posicionamento de dispositivos móveis que utilizam microrreceptor GNSS, utilizando a estimativa de mínimos quadrados recursiva com a matriz de ganho de Kalman aplicada no posicionamento relativo estático por dupla diferença da pseudodistância em linhas de base curtas. Para verificar a eficácia desta metodologia utilizou-se dados do microrreceptor SiRFstar IV que recebe dados na frequência L1 da constelação GPS. Foram utilizadas as estações de referência da RBMC para o processamento destes dados. Com rastreios de 15 minutos em pontos de coordenadas conhecidas teve-se um desvio médio na componente horizontal das coordenadas planas de 29 centímetros para o pós- processamento e 98 centímetros para o processamento em tempo real, sendo que, para o posicionamento por ponto simples o desvio médio foi de 6 metros. Com isso, concluiu-se que a utilização da metodologia de processamento relativo estático por estimativa dos mínimos quadrados recursiva melhorou a acurácia do posicionamento de forma significativa, onde dispositivos móveis 14que até então eram indicados somente para navegação podem ser utilizados também para mapeamento.
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Variáveis canônicas não singulares e o movimento rotacional de satélites artificiaisSimal Moreira, Leonardo [UNESP] 06 1900 (has links) (PDF)
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simalmoreira_l_me_guara.pdf: 2039741 bytes, checksum: 40e1e56a7f2c21c69823f17d854f8994 (MD5) / Universidade Estadual Paulista (UNESP) / A atitude de um satélite artificial representa sua orientação no espaço, de modo que através da atitude pode-se conhecer a orientação espacial do satélite pela relação entre dois sistemas de coordenadas, um dels fixo no corpo do setélite e o outro associado com umsistema de referência inercial. Apesar da atitude ser bem representada por vários conjuntos de variáveis, todos estes apresentam limitações em sua utilização. Focaliza-se neste trabalho um conjunto de variáveis canônicas não singulares, aplicáveis ao movimento racional de satélites artificiais. Estas variáveis são úteis para o caso em que o vetor momento angular de rotação coincide com o maior momento principal de inércia do satélite. As equações dinâmicas do movimento rotacional são deduzidas pelo formalismo hamiltoniano e então integradas para análise do movimento rotacional livre de torques externos. Soluções analíticas aproximadas são obtidas e comparadas com as soluções gerais, representadas em funções elípticas, e com soluções numéricas. A Hamiltoniana média associada ao Torque de Gradiente de Gravidade é também incluida e as equações diferenciais do movimento pertubado são deduzidas em termos das variáveis não singulares. A integração analítica e numérica destas equações permite uma análise qualitativa e quantitativa das variáveis não singulares utilizadas para o movimento rotacional, quando se considera a pertubação provocada pelo Torque da Gradiente de Gravidade. Ao mesmo tempo esta análise aponta para limitações de intervalos de tempo em que algumas soluções devem ser utilizadas. Aplicações são realizadas para satélites com características similares as dos Satélites Brasileirs de Coleta de Dados (SCD1 e SCD2). / The attitude of an artificial satellite represents its orientation in the space, in way that through the attitude can be known the spatial orientation of the satellite for the relation between two systems of coordinates, one of them fixed in the satellite and other associate with an Inertial Referencce System. Many sets of variables are used to represent the satellite attitude, but some of them present limitations in its use. A set of non-singular canonical variables, applicable to the rotational motion of artificial satellites, is focused in this work. Thse variables are useful for the case where the rotational angular momentum vector coincides with the biggest principal moment of inertia of the satellite. The dynamic equations of the rotational motion are deduced by the Hamiltonian formalism and then they are integrated for the analysis of the torque-free rotational motion. Approximated analytical solutions are gotten and compared with the general solutions and numerical solutions. The associated mean Hamiltonian to the Gravity Gradient Torque also enclosed and the differential equations of the motion are deduced for the non-singular variables. The analytical and numeical integration of these equations allow a qualitative and quantitative analysis of these non-singular variables, when the disturbance of the Gravity Gradiente Torque is considered. At the same time this analysis point to limitations of time intervals where some solutions must be used. Applications are done for the satellite with similar characteristics of the Brzilian Satellites of Collection of Data (SCD1 and SCD2).
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Dinâmica ressonante de alguns satélites artificiais terrestres no sistema Terra-Lua-SolMerguizo Sanchez, Diogo [UNESP] 22 December 2009 (has links) (PDF)
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merguizosanchez_d_me_rcla.pdf: 2937684 bytes, checksum: 8831a2baec961b9a95e300124d0b3a90 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / A estabilidade dos membros das constelações Galileo e GPS é investigada. Devido à ressonância 2:1 entre w e W, ocorre um aumento significativo da excentricidade. Este aumento causa riscos de colisão entre os satélites descartáveis e os ativos. Como a ressonância não depende do semi–eixo do satélite, estratégias usuais de aumentar a altitude não resolvem o problema. Então, condições iniciais especiais são achadas tais que os satélites descartáveis permanecem estáveis, com baixa excentricidade por pelo menos 250 anos. Outra estratégia de atacar o problema é mover o objeto descartável para uma órbita particular, acelerando o crescimento da excentricidade. Este estudo é brevemente apresentado. A dinâmica de satélites heliossíncronos é também estudada. Devido o arrasto atmosférico, a altitude do satélite sempre decai e portanto ele cruza o valor ressonante do semi-eixo. Sempre que isso ocorre, um salto na inclinação é observado e em alguns casos, há alguns cruzamentos tais que a inclinação permanece aprisionada (durante algum tempo) no centro de libração. Este evento é importante, pois isso pode ser explorado para realizar manobras de baixo custo para controlar o satélite numa determinada inclinação. Através do sistema exato, investigamos estas quasecapturas e seu aproveitamento em manobras de manutenção de inclinação. / The stability of the disposed members of the Galileo and GPS constellations is investigated. Due to the 2:1 resonance between w and W, a significant increase of the eccentricity occurs. These increase cause risk of collisions between the operational and disposed satellites. As the resonance does not depend on the semi-major axis of the satellite, usual strategies of raising the altitude do not solve the problem. Therefore, special initial conditions are found such that the disposed satellites remain stable with small eccentricity, for at least 250 years. Another strategy to attack the problem is to move the disposed object to a particular orbit, accelerating the growth of the eccentricity. This study is briefly presented. The dynamics of the sun-synchronous satellite is also studied. Due to the atmospheric drag, the altitude of the satellite always decays and therefore it crosses the resonant value of the semi-major axis. Whenever this happens, a jump in the inclination is observed and in some cases, there are some crossing such that the inclination remains locked (during some time) in the center of the libration. This event is interesting since it can be exploited to perform inexpensive maneuvers to control the satellite at desired inclination.
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