The Global Positioning System (GPS) has been widely used for precise positioning applications throughout the world. However, there are still some limiting factors that affect the performance of satellite-based positioning techniques, including the ionosphere. The GPS Network-RTK (NRTK) concept has been developed in an attempt to remove the ionospheric bias from user observations within the network. This technique involves the establishment of a series of GNSS reference stations, spread over a wide geographical region. Real time data from each reference station is collected and transferred to a computing facility where the various spatial and temporal errors affecting the GNSS satellite observations are estimated. These corrections are then transmitted to users observations in the field. As part of a Victorian state government initiative to implement a cm-level real time positioning service state-wide, GPSnet is undergoing extensive infrastructure upgrades to meet high user demand. Due to the sparse (+100km) configuration of GPSnet's reference stations, the precise modelling of Victoria's ionosphere will play a key role in providing this service. This thesis aims is to develop a temporal model for the ionospheric bias within a Victorian NRTK scenario. This research has analysed the temporal variability of the ionosphere over Victoria. It is important to quantify the variability of the ionosphere as it is essential that NRTK corrections are delivered sufficiently often with a small enough latency so that they adequately model variations in the ionospheric bias. This will promote the efficient transmission of correctional data to the rover whilst still achieving cm-level accuracy. Temporal analysis of the ionosphere revealed that, during stable ionospheric conditions, Victoria's double differenced ionospheric (DDI) bias remains correlated to within +5cm out to approximately two minutes over baselines of approximately 100km. However, the data revealed that during more disturbed ionospheric conditions this may decrease to one minute. As a preliminary investigation, four global empirical ionospheric models were tested to assess their ability to estimate the DDI bias. Further, three temporal predictive modelling schemes were tested to assess their suitability for providing ionospheric corrections in a NRTK environment. The analysis took place over four seasonal periods during the previous solar maximum in 2001 and 2002. It was found that due to the global nature of their coefficients, the four global empirical models were unable to provide ionospheric corrections to a level sufficient for precise ambiguity resolution within a NRTK environment. Three temporal ionospheric predictive schemes were developed and tested. These included a moving average model, a linear model and an ARIMA (Auto-Regressive Integrated Moving Average) time series analysis. The moving average and ARIMA approaches gave similar performance and out-performed the linear modelling scheme. Both of these approaches were able to predict the DDI to +5cm within a 99% confidence interval, out to an average of approximately two minutes, on average 90% of the time when compared to the actual decorrelation rates of the ionosphere. These results suggest that the moving average scheme, could enhance the implementation of next generation NRTK systems by predicting the DDI bias to latencies that would enable cm-level positioning.

Real-Time Kinematic (RTK) positioning is a technique used to provide precise positioning services at centimetre accuracy level in the context of Global Navigation Satellite Systems (GNSS). While a Network-based RTK (N-RTK) system involves multiple continuously operating reference stations (CORS), the simplest form of a NRTK system is a single-base RTK. In Australia there are several NRTK services operating in different states and over 1000 single-base RTK systems to support precise positioning applications for surveying, mining, agriculture, and civil construction in regional areas. Additionally, future generation GNSS constellations, including modernised GPS, Galileo, GLONASS, and Compass, with multiple frequencies have been either developed or will become fully operational in the next decade. A trend of future development of RTK systems is to make use of various isolated operating network and single-base RTK systems and multiple GNSS constellations for extended service coverage and improved performance. Several computational challenges have been identified for future NRTK services including: • Multiple GNSS constellations and multiple frequencies • Large scale, wide area NRTK services with a network of networks • Complex computation algorithms and processes • Greater part of positioning processes shifting from user end to network centre with the ability to cope with hundreds of simultaneous users’ requests (reverse RTK) There are two major requirements for NRTK data processing based on the four challenges faced by future NRTK systems, expandable computing power and scalable data sharing/transferring capability. This research explores new approaches to address these future NRTK challenges and requirements using the Grid Computing facility, in particular for large data processing burdens and complex computation algorithms. A Grid Computing based NRTK framework is proposed in this research, which is a layered framework consisting of: 1) Client layer with the form of Grid portal; 2) Service layer; 3) Execution layer. The user’s request is passed through these layers, and scheduled to different Grid nodes in the network infrastructure. A proof-of-concept demonstration for the proposed framework is performed in a five-node Grid environment at QUT and also Grid Australia. The Networked Transport of RTCM via Internet Protocol (Ntrip) open source software is adopted to download real-time RTCM data from multiple reference stations through the Internet, followed by job scheduling and simplified RTK computing. The system performance has been analysed and the results have preliminarily demonstrated the concepts and functionality of the new NRTK framework based on Grid Computing, whilst some aspects of the performance of the system are yet to be improved in future work.

Made available in DSpace on 2014-06-11T19:22:25Z (GMT). No. of bitstreams: 0 Previous issue date: 2010-05-28Bitstream added on 2014-06-13T20:28:45Z : No. of bitstreams: 1 barbosa_em_me_prud.pdf: 6325120 bytes, checksum: 83ca12d41a1c8b2c08c84707b01d7e4c (MD5) / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Os avanços tecnológicos nos métodos de posicionamento têm possibilitado o desenvolvimento de metodologias que viabilizam a sua utilização pelo usuário numa diversidade de aplicações. Um dos métodos de posicionamento GNSS (Global Navigation Satellite System) de grande destaque é o RTK (Real Time Kinematic) utilizando o conceito de rede de estações. Esse método utiliza a infra-estrutura de uma rede de estações de referência, para disponibilizar correções ao usuário. O conceito clássico do RTK tem como princípio básico a alta correlação dos erros provocados pela ionosfera, troposfera e órbita dos satélites na estação de referência e em uma estação próxima de interesse. No entanto, com o afastamento entre o usuário e a estação base, a eficiência do método é degradada, pois a correlação dos erros é reduzida. Mas, quando se utiliza uma rede de estações de referência, pode-se realizar a modelagem dos erros na área de abrangência da rede. Esta concepção é denominada de RTK em Rede. No que concerne a rede de estações de referência GNSS, utilizou-se a rede estabelecida no oeste do estado de São Paulo (rede GNSS-SP). O software adotado para realizar o processamento em rede foi o GPSNet na versão 2.73. Outra questão levantada foi com relação aos padrões disponíveis para a transmissão dos dados ao usuário, tais como o RTCM e CMR, mostrando as evoluções e aplicações. A questão do enlace de comunicação (link) também foi abordada, mostrando os principais tipos disponíveis, mas com ênfase na telefonia móvel que foi utilizada para transmitir os dados via internet. Foram conduzidos vários experimentos... / Technological advances in positioning methods have enabled the development of methodologies that allow its use in a great variety of applications. One method of GNSS (Global Navigation Satellite System) positioning of high performance is the RTK (Real Time Kinematic) network. This method uses the infrastructure of a network of reference stations. The original concept of RTK is the high correlation of the errors caused by ionosphere, troposphere and satellite orbit at a reference station and at a nearby station of interest. However, increasing the distance between the user and the base station, the efficiency of the method is degraded, because the error correlation is reduced. But when using a network of reference stations, a better error modeling in the area of the network is possible. This concept is the so called Network RTK. Regarding the network of GNSS reference stations, in this work the established network in the western state of São Paulo (GNSS network-SP) was used. The software adopted to perform the tests in the network was that GPSNet, version 2.73. Another issue raised during the investigation was related to the available standards for transmitting data to the user, such as CMR and RTCM. The developments and applications were presented. The issue of communication link (link) has been addressed, showing the main available types, but with emphasis on mobile phone that was the technology used to transmit data via the Internet. Several experiments were conducted in different locations to examine the integrity, availability and accuracy for RTK positioning and RTK network. The experiments performed with RTK and RTK network (using the concept of VRS (Virtual Reference Station)) showed some problems, probably related to the density of the network. Among them the accuracy, the initialization time span more than expected or even... (Complete abstract click electronic access below)

Network RTK is a real-time technique for accurate positioning with Global Navigation Satellite Systems (GNSS). The technology means the use of correction data from a network of GNSS receivers with known positions (reference stations) to reduce the uncertainty in position for the user´s GNSS receiver (rover). However, this requires that the correction data can be transferred seamlessly to the user in real time. Commonly the corrections are transferred via mobile phones. The Swedish National Land Survey operates a nationwide Network RTK service, where users can receive correction data via GSM or mobile Internet (GPRS). Network RTK service is based on a nationwide network of permanent reference stations for GNSS, SWEPOS which is also used for other applications. The aim of the study is to examine how the delay and loss in the transmission of network corrections affect measurement with Network RTK service from SWEPOS. Three receivers of different types, Trimble, Topcon and Leica were used to receive signals (all three at the same time) via a fixed external GNSS antenna with very good receiving conditions. Special software was used to create delays and loss of correction data from correction data to the three receivers.   The results show that the threshold where delay and loss means that receivers can no longer calculate a precise position varies between brands. Leica was the most sensitive to loss of correction data, Trimble for delays, while Topcon held up well for both. A new initialization requires that data loss and delay are not too large. Position deviations due to loss and delay of correction data indicate a significant difference between radial plane deviations and height deviations, especially at high loss of correction data. Delays of 0–4 s and various losses of correction data have generally small impact on the standard uncertainty values ​​in latitude and longitude. The standard uncertainty in height is 1.5–2 times higher than it is in plane. The impact of the baseline length is not significant, a marginal increase in the standard uncertainty was seen when increasing from 10 km to 30 km. / Nätverks-RTK är en realtidsteknik för noggrann positionering med hjälp av Global Navigation Satellite Systems (GNSS). Tekniken innebär att användaren utnyttjar korrektionsdata från ett nätverk av GNSS-mottagare med kända positioner (referensstationer) för att minska osäkerheten i positionen för den egna GNSS-mottagaren (rover). Detta ställer dock krav på att korrektionsdata kan överföras problemfritt till användaren i realtid. Vanligen sker den överföringen via mobiltelefoni. Lantmäteriet driver en rikstäckande nätverks-RTK-tjänst, där användarna kan erhålla korrektionsdata via GSM eller mobilt Internet (GPRS). Nätverks-RTK-tjänsten baseras på ett rikstäckande nät av fasta referensstationer för GNSS, SWEPOS, vilket också används för andra tillämpningar.   Syftet med studien är att undersöka hur fördröjning och bortfall i överföringen av nätverkskorrektioner påverkar mätning med SWEPOS nätverks-RTK-tjänst. För det ändamålet användes tre mottagare av fabrikaten Leica, Trimble och Topcon som parallellt tog emot signaler via en fast extern GNSS-antenn under mycket goda mottagningsförhållanden. En särskild programvara användes för att skapa fördröjningar och bortfall av korrektionsdata till de tre mottagarna.   Resultaten visade att tröskelvärdet, där fördröjning och bortfall gör att mottagarna inte längre kan beräkna en noggrann position, varierade mellan fabrikaten. Leica var mest känslig för bortfall, Trimble för fördröjningar, medan Topcon stod sig bra för båda. Vid ny initialisering av fixlösning krävdes att databortfall och fördröjning inte var för stora för någon av fabrikaten. Positionsavvikelserna beroende på bortfall och fördröjning av korrektionsmeddelanden visar på en signifikant skillnad mellan radiella planavvikelser och höjdavvikelser, speciellt vid höga bortfall. Fördröjningar på 0–4 s och olika bortfall har generellt liten påverkan på standardosäkerheternas värden i latitud- och longitudled. I höjdled är genomgående standardosäkerheten 1,5–2 gånger större än vad den är i planled. Baslinjelängdens betydelse är inte så stor, en marginell ökning av standardosäkerheten kunde ses vid ökning från 10 km till 30 km.

Orientador: João Francisco Galera Monico / Banca: Leonardo Castro de Oliveira / Banca: Mauro Issamu Ishikawa / Resumo: Os avanços tecnológicos nos métodos de posicionamento têm possibilitado o desenvolvimento de metodologias que viabilizam a sua utilização pelo usuário numa diversidade de aplicações. Um dos métodos de posicionamento GNSS (Global Navigation Satellite System) de grande destaque é o RTK (Real Time Kinematic) utilizando o conceito de rede de estações. Esse método utiliza a infra-estrutura de uma rede de estações de referência, para disponibilizar correções ao usuário. O conceito clássico do RTK tem como princípio básico a alta correlação dos erros provocados pela ionosfera, troposfera e órbita dos satélites na estação de referência e em uma estação próxima de interesse. No entanto, com o afastamento entre o usuário e a estação base, a eficiência do método é degradada, pois a correlação dos erros é reduzida. Mas, quando se utiliza uma rede de estações de referência, pode-se realizar a modelagem dos erros na área de abrangência da rede. Esta concepção é denominada de RTK em Rede. No que concerne a rede de estações de referência GNSS, utilizou-se a rede estabelecida no oeste do estado de São Paulo (rede GNSS-SP). O software adotado para realizar o processamento em rede foi o GPSNet na versão 2.73. Outra questão levantada foi com relação aos padrões disponíveis para a transmissão dos dados ao usuário, tais como o RTCM e CMR, mostrando as evoluções e aplicações. A questão do enlace de comunicação (link) também foi abordada, mostrando os principais tipos disponíveis, mas com ênfase na telefonia móvel que foi utilizada para transmitir os dados via internet. Foram conduzidos vários experimentos... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Technological advances in positioning methods have enabled the development of methodologies that allow its use in a great variety of applications. One method of GNSS (Global Navigation Satellite System) positioning of high performance is the RTK (Real Time Kinematic) network. This method uses the infrastructure of a network of reference stations. The original concept of RTK is the high correlation of the errors caused by ionosphere, troposphere and satellite orbit at a reference station and at a nearby station of interest. However, increasing the distance between the user and the base station, the efficiency of the method is degraded, because the error correlation is reduced. But when using a network of reference stations, a better error modeling in the area of the network is possible. This concept is the so called Network RTK. Regarding the network of GNSS reference stations, in this work the established network in the western state of São Paulo (GNSS network-SP) was used. The software adopted to perform the tests in the network was that GPSNet, version 2.73. Another issue raised during the investigation was related to the available standards for transmitting data to the user, such as CMR and RTCM. The developments and applications were presented. The issue of communication link (link) has been addressed, showing the main available types, but with emphasis on mobile phone that was the technology used to transmit data via the Internet. Several experiments were conducted in different locations to examine the integrity, availability and accuracy for RTK positioning and RTK network. The experiments performed with RTK and RTK network (using the concept of VRS (Virtual Reference Station)) showed some problems, probably related to the density of the network. Among them the accuracy, the initialization time span more than expected or even... (Complete abstract click electronic access below) / Mestre

Network-RTK is a method of relative measuring using GNSS that provides users in alarge area with an easy way obtaining low uncertainties in their measurements. Regularnetwork-RTK does not meet the requirements of the Swedish Transport Administration(STA) regarding its larger and/or more complex projects, leading to the concept ofproject-based network-RTK being introduced in Sweden by the STA, in collaborationwith the network-RTK service provider SWEPOS back in 2004. This concept improvesupon regular network-RTK by decreasing the uncertainties and increasing reliabilitieswithin the project area. SWEPOS has since the collaboration back in 2004 supplied theSTA with project-based network-RTK services.The market is not the same today as it was in 2004 and there are more service providersactive in Sweden. This thesis intends to find out if this new market means that there areother alternatives to SWEPOS with regards to the STA’s requirements for project-basednetwork-RTK. This is done through a technical comparison of the different serviceprovider’s measurement uncertainties and their measurement accuracies as well as acomparison of their surrounding infrastructure and the subjective user experience.Similar studies have been conducted before (Edwards et al., 2010) (Martin andMacGovern, 2012) (Saeidi, 2012), but never in Sweden nor with SWEPOS as one of theservice providers as it is only available in Sweden. Neither have they had a focus onmeasurement uncertainties and accuracies in a project-based network-RTK net. Theyhave all concluded that there were no significant differences between any of the serviceproviders compared, in both the measurement uncertainties and accuracies.For the technical part of this thesis, measurements were conducted at four sites: two atdifferent locations within the area of a former, STA project-site, one within the regularnet and the final site outside the entire net, with the amount of collected data varying forthe different sites. Five different GNSS receivers of different brands were used for themeasurements to make it as general as possible.The results show that there are slight differences in the height uncertainty, but the scopeof this thesis does not permit the full correlation study needed to determine if thesedifferences are significant. There does not seem to be any differences in the accuracies ofthe service provider. Some of the sites with less data collected show contradictoryevidence to this statement, but it is deemed that these deviations are more likely relatedto something other than the service providers, such as human interference or errors.Large differences exist in the user experience and surrounding infrastructure, an areawhere SWEPOS at the moment has a clear lead. This is believed to be due to SWEPOSprimarily being a network-RTK service provider and thus allocating more resources andpersonnel, whilst the other service providers also serve as equipment vendor andmaintainers.Combining the two comparison parts leads to the overall conclusion that with theservice providers in their current state with the requirements of the STA specified intheir current state, only SWEPOS is a viable alternative as a supplier of project-basednetwork-RTK. But this is something that could change with relative ease depending on ifthe other service providers allocate more resources. / Nätverks-RTK är en metod för relativ mätning med hjälp av GNSS som ger användare istora områden ett enkelt sätt att förbättra osäkerheterna i sina mätningar. I början av2000 talet då frågan om alternativa lösningar till stomnät på marken aktualiseradesuppfyllde inte tillgängliga nätverks-RTK-lösningar Trafikverkets (TrV) krav påmätningar när det gäller dess större och/eller mer komplexa projekt. Något som leddetill att konceptet projektbaserad nätverks-RTK infördes i Sverige av TrV i samarbetemed tjänsteleverantören SWEPOS 2004. Detta koncept förbättrar vanlig nätverks-RTKgenom att minska osäkerheterna ytterligare och öka tillförlitligheten inom ett mindreprojektområde. SWEPOS har sedan detta samarbete 2004 levererat projektbaseradenätverks-RTK tjänster till TrV.Marknaden är inte samma dag som den var 2004 och det finns fler verksammatjänsteleverantörer i Sverige. Detta examensarbete avser att ta reda på om denna nyamarknad innebär att det finns andra alternativ till SWEPOS med avseende på de kravTrV har på projektbaserad nätverks-RTK. Något som sker genom en teknisk jämförelseav de olika tjänsteleverantörernas mätosäkerheter och deras noggrannheter samt enjämförelse av deras omgivande infrastruktur och den subjektiva användarupplevelsen.Liknande studier har gjorts tidigare (Edwards et al., 2010) (Martin och MacGovern2012) (Saeidi, 2012), men aldrig i Sverige och med SWEPOS som ett avjämförelseobjekten. De har inte heller haft fokus på mätosäkerheter och noggrannheterunder projektbaserade nätverks-RTK förhållanden. De har alla haft samma slutsats: attdet inte finns några signifikanta skillnader mellan de jämförda tjänsteleverantörerna.För den tekniska jämförelsen har mätningar utförts på fyra platser: två inom ettbefintligt TrV projektområde, en i det ordinarie nätet och den sista utanför hela nätet,där den insamlade datamängden varierar för de olika platserna. Fem olika GNSSmottagareav olika märken användes för att göra mätningarna så allmänna som möjligt.Resultaten visar att det finns små osäkerhetsskillnader i höjd, men för att avgöra omdessa skillnader är signifikanta eller ej så skulle en fullständig korrelationsanalys av deolika tjänsteleverantörerna behövas, något som inte ryms inom detta arbete. Det verkarinte heller finnas några signifikanta skillnader i noggrannhet hos tjänsteleverantören.Några av platser med mindre mängd insamlad data uppvisar motsägande resultat, mendetta bedöms bero mer på andra faktorer än tjänsteleverantörer i sig, såsom mänskligpåverkan etc.Användarupplevelsen och tjänsteleverantörernas omgivande infrastruktur uppvisarstörre skillnader, där SWEPOS för tillfället har ett klart övertag. Detta tros bero påSWEPOS främst är en tjänsteleverantör av nätverks-RTK och därmed har merdedikerade resurser och personal, men de andra tjänsteleverantörerna även agerarleverantörer/försäljare av utrustning.En kombination av de två jämförelsedelarna leder till en mer generell slutsats att medalla tjänsteleverantörer i sina nuvarande tillstånd alternativt utan en eventuellomformulering av TrVs krav, är enbart SWEPOS ett alternativ som leverantör avprojektbaserad nätverks-RTK lösningar till TrV. Men detta är något som kan förändrasmed relativ snabbt beroende på om andra tjänsteleverantörerna avsätter mer resursereller om kraven formuleras om.

<p>Från den 1 april 2006 har SWEPOS kompletterat den befintliga nätverks-RTK-tjänsten, som dittills levererat RTK-data för GPS, med ett alternativ där RTK-data för GPS/GLONASS levereras. En del användare har rapporterat att de upplever att GPS/GLONASS inte tillför något och även att det ibland kan ta längre tid att få fixlösning. Andra användare hävdar att de nu kan använda nätverks-RTK på platser där de tidigare inte kunde mäta och är mycket positiva till GPS/GLONASS.</p><p>Syftet med detta examensarbete var att undersöka hur tillgängligheten för satellitmätning, positionsnoggrannheten och initialiseringstiden påverkades i öppna respektive störda miljöer med GPS/GLONASS jämfört med enbart GPS vid användandet av nätverks-RTK-tjänsten. Undersökningen har utförts med tre olika fabrikat av GNSS-mottagare (Leica, Topcon och Trimble), vilket även medger att en jämförelse mellan dessa till viss utsträckning kan göras.</p><p>I studien gjordes totalt 1 440 mätningar på sex punkter med kända positioner och med olika grad av sikthinder. Fixlösning uppnåddes inte inom 180 sekunder för 206 (77 för GPS/GLONASS och 129 för GPS) av de 1 440 mätningarna.</p><p>De extra GLONASS-satelliterna tillför en klar fördel när det gäller möjligheten att mäta i störda miljöer. När det gäller initialiseringstid så är dessa kortare för GPS/GLONASS. GLONASS-satelliterna ger ingen förbättring av positionsnoggrannheten. Det är till och med så att GPS får något bättre kvalitetstal i både plan och höjd i denna studie (1-3 mm bättre). För de olika fabrikaten kan det konstateras att precision och noggrannhet är likvärdiga i både plan och höjd för alla tre märken.</p> / <p>On the 1st of April 2006, SWEPOS complemented the existing network RTK service with corrections for the Russian satellite system GLONASS. The service had so far only provided corrections for GPS. Some users have claimed that GPS/GLONASS do not contribute at all and also that the time for initialization sometimes can be longer. However, other users insist on that they now can use network RTK in areas that earlier were impossible and they are very favourable of GPS/GLONASS.</p><p>The purposes of this diploma work were to study and examine measurements using GPS and GPS/GLONASS in areas with different degrees of visual obstacles. Corrections were provided by SWEPOS Network RTK service and availability of satellites, accuracy of position and time for initialization were evaluated. The study has been conducted with three different brands of GNSS receivers (Leica, Topcon and Trimble), which also to some extent makes a comparison between the three brands possible.</p><p>A total number of 1 440 field measurements were made on six well-known points with different degrees of visual obstacles. A fixed solution was not accomplished within 180 seconds for 206 (77 for GPS/GLONASS and 129 for GPS) of the 1 440 measurements.</p><p>The additional GLONASS satellites provide an apparent advantage regarding the possibility to measure in disturbed environments. The time for initialization is shorter for GPS/GLONASS. The GLONASS satellites do not give any improvement in accuracy of position. On the contrary, GPS receives slightly better accuracy numbers in quality for both horizontal and vertical readings (1-3 mm better). Regarding the different brands, it was found that the precision and accuracy were similar in both plane and height for all three brands.</p>

Från den 1 april 2006 har SWEPOS kompletterat den befintliga nätverks-RTK-tjänsten, som dittills levererat RTK-data för GPS, med ett alternativ där RTK-data för GPS/GLONASS levereras. En del användare har rapporterat att de upplever att GPS/GLONASS inte tillför något och även att det ibland kan ta längre tid att få fixlösning. Andra användare hävdar att de nu kan använda nätverks-RTK på platser där de tidigare inte kunde mäta och är mycket positiva till GPS/GLONASS. Syftet med detta examensarbete var att undersöka hur tillgängligheten för satellitmätning, positionsnoggrannheten och initialiseringstiden påverkades i öppna respektive störda miljöer med GPS/GLONASS jämfört med enbart GPS vid användandet av nätverks-RTK-tjänsten. Undersökningen har utförts med tre olika fabrikat av GNSS-mottagare (Leica, Topcon och Trimble), vilket även medger att en jämförelse mellan dessa till viss utsträckning kan göras. I studien gjordes totalt 1 440 mätningar på sex punkter med kända positioner och med olika grad av sikthinder. Fixlösning uppnåddes inte inom 180 sekunder för 206 (77 för GPS/GLONASS och 129 för GPS) av de 1 440 mätningarna. De extra GLONASS-satelliterna tillför en klar fördel när det gäller möjligheten att mäta i störda miljöer. När det gäller initialiseringstid så är dessa kortare för GPS/GLONASS. GLONASS-satelliterna ger ingen förbättring av positionsnoggrannheten. Det är till och med så att GPS får något bättre kvalitetstal i både plan och höjd i denna studie (1-3 mm bättre). För de olika fabrikaten kan det konstateras att precision och noggrannhet är likvärdiga i både plan och höjd för alla tre märken. / On the 1st of April 2006, SWEPOS complemented the existing network RTK service with corrections for the Russian satellite system GLONASS. The service had so far only provided corrections for GPS. Some users have claimed that GPS/GLONASS do not contribute at all and also that the time for initialization sometimes can be longer. However, other users insist on that they now can use network RTK in areas that earlier were impossible and they are very favourable of GPS/GLONASS. The purposes of this diploma work were to study and examine measurements using GPS and GPS/GLONASS in areas with different degrees of visual obstacles. Corrections were provided by SWEPOS Network RTK service and availability of satellites, accuracy of position and time for initialization were evaluated. The study has been conducted with three different brands of GNSS receivers (Leica, Topcon and Trimble), which also to some extent makes a comparison between the three brands possible. A total number of 1 440 field measurements were made on six well-known points with different degrees of visual obstacles. A fixed solution was not accomplished within 180 seconds for 206 (77 for GPS/GLONASS and 129 for GPS) of the 1 440 measurements. The additional GLONASS satellites provide an apparent advantage regarding the possibility to measure in disturbed environments. The time for initialization is shorter for GPS/GLONASS. The GLONASS satellites do not give any improvement in accuracy of position. On the contrary, GPS receives slightly better accuracy numbers in quality for both horizontal and vertical readings (1-3 mm better). Regarding the different brands, it was found that the precision and accuracy were similar in both plane and height for all three brands.

Sammanfattning   Förutsättning   I examensarbetet har det ingått ett verkligt ärende som handläggs av mig som MBK-ingenjör inom Lantmäteriet. Det är ett naturvårdsuppdrag från Länsstyrelsen och innefattar bl a inmätning och utstakning av gräns på ett blivande naturreservat.   Naturvårdsuppdraget Huskeberget ligger ca 5 km norr om Södra Finnskoga och sydväst om Höljes i norra Värmland. Omkrets 2,38 km. Områdets höjd är ca 550 m över havet och ligger på sydöstra sluttningen av Huskeberget.   Fix   Lantmäteriet använder idag Leica Viva CS15/GS15 mätutrustning vid inmätning av brytpunkter och gränser. I detta fall det blivande naturreservatet. Under vissa omständigheter kan det ta tid att få fix-lösning eller helt utebli. Dessa omständigheter kan bero på ett flertal faktorer bl a kraftiga jonosfärsstörningar och/eller GPRS-nätets täckningsområde för mottagning av SWEPOS nätverks-RTK tjänst.   Inriktning   Fokus har lagts på att utvärdera ett alternativ till nätverks-RTK, en sk enkelstations-RTK med uppkoppling till en tillfällig referensstation.   Närmare undersökning har gjorts på tiden för initialisering vid varje enskild inmätning som sedan jämförts i de två mätmetoderna. Tiden för själva arbetet sätts sedan i relation till resultatet från undersökningen för att ge en helhetsbild av tidsåtgång i arbetet med vardera mätmetoden.   Resultat   Efter alla brytpunkter mätts in visade det sig att i just det här området inte fanns några anmärkningsvärda problem att få fix-lösning med någon av de valda mätmetoderna. Resultatet visar därmed små skillnader i tidsjämförelser.   En oplanerad testmätning med nätverks-RTK gjordes i tät skog alldeles intill en inmätt brytpunkt utan framgång att få fix-lösning. Detta för att belysa problematiken med att få fix-lösning vid mätning i tät skog.   Rapporten innehåller en kortfattad beskrivning av delar av arbetet i Lantmäteriets handläggning av naturvårdsuppdrag.

Many high-accuracy regional GPS continuously operating reference (CORS) networks have been established globally. These networks are used to facilitate better positioning services, such as high accuracy real-time positioning. GPSnet is the first state-wide CORS network in Australia. In order to maximize the benefits of the expensive CORS geospatial infrastructure, the state of Victoria in collaboration with three universities (RMIT University, the University of NSW and the University of Melbourne) embarked on research into regional atmospheric error modelling for Network-based RTK (NRTK) via an Australian Research Council project in early 2005. The core of the NRTK technique is the modelling of the spatially-correlated errors. The accuracy of the regional error model is a determining factor for the performance of NRTK positioning. In this research, a number of error models are examined and comprehensively analysed. Among them, the following three models are tested: 1) the Linear Interpolation Method (LIM); 2) the Distance-Based interpolation method (DIM); and 3) the Low-order surface model (LSM). The accuracy of the three models is evaluated using three different observation sessions and a variety of network configurations of GPSnet. Results show that the LIM and DIM can be used to significantly reduce the double-differenced (DD) residuals (up to 60% improvement), and the LIM is slightly better than the DIM (most at mm level). However the DD residuals with the LSM corrections are, in some cases, not only much worse than that of the LIM and DIM but also even must greater/worse than the DD residuals without any corrections applied at all. This indicates that there are no advantages by using the LSM for the error modelling for NRTK in GPSnet, even though it is the most commonly used method by researchers. The performance difference of the LIM for different GPSnet configurations is also tested. Results show that in most cases, the performance difference mainly caused by the number of reference stations used is not significant. This implies that more redundant reference stations may not contribute much to the accuracy improvement of the LIM. However, it may mitigate the station specific errors (if any). The magnitude of the temporal variations of both the tropospheric and ionospheric effects in GPSnet observations is also investigated. Test results suggest that the frequency of generating and transmitting the tropospheric corrections should not be significantly different from that for the ionospehric corrections. Thus 1Hz frequency (i.e. once every second) is recommended for the generation and transmission for both types of the atmospheric corrections for NRTK in GPSnet. The algorithms of the NRTK software package used are examined and extensive analyses are conducted. The performance and limitation of the NRTK system in terms of network ambiguity resolution are assessed. The methodology for generating virtual reference station (VRS) observations in the system is presented. The validation of the algorithms for the generated VRS observations is undertaken. It is expected that this research is significant for both the selection of regional error models and the implementation of the NRTK technique in GPSnet or in the Victorian region.