Cost-effective GNSS receivers for geodetic monitoring : doctoral dissertation

Hamza, Veton (author), Stopar, Bojan (mentor), Sterle, Oskar (comentor), Kozmus Trajkovski, Klemen (member of the commission for defense), Kuhar, Miran (member of the commission for defense), Cefalo, Raffaela (member of the commission for defense)

For numerous years, geodetic techniques and sensors have been applied to determine and monitor deformations of engineering structures and natural hazards. GNSS instruments have been classified as suitable sensors for monitoring applications due to their ability to provide continuous monitoring of movements with high accuracy. Nevertheless, the implementation of geodetic GNSS instruments in high-risk areas may be deemed costly, with prices ranging up to several tens of thousands of euros. In certain situations, multiple GNSS instruments need to be installed, further increasing the cost by several hundred thousand euros. Instead, low-cost GNSS receivers are being considered as an alternative to high-quality geodetic GNSS receivers for such applications. A few years ago (in 2019), low-cost dual-frequency GNSS receivers were introduced to the market, drawing the attention of numerous researchers in the geodetic field. These GNSS receivers, capable of tracking satellite signals in both frequencies, offer the advantage of compensating for the ionospheric delay, leading to their increased use across different applications. Low-cost GNSS instruments now have the ability to provide real-time kinematic (RTK) positioning solutions and are compatible with geodetic GNSS antennas, making them comparable to high-quality geodetic GNSS instruments. The findings of the doctoral dissertation indicate that low-cost GNSS instruments currently do not provide observations of the same quality as geodetic GNSS instruments, but rather slightly inferior. Nevertheless, these GNSS sensors can obtain positioning with an accuracy that is acceptable for many survey projects. Low-cost GNSS instruments were used to develop a low-cost GNSS monitoring system for geodetic monitoring applications. The developed LGMS represents a suitable solution for near realtime continuous monitoring with high accuracy while significantly reducing costs. To validate its performance, the LGMS was tested in monitoring the Laze landslide over six months from where its functionality was proven. Furthermore, it can be applied for monitoring other engineering structures such as viaducts, bridges, dams, mining areas, and chimneys, as well as natural hazards like subsidence and landslides, provided it meets the accuracy requirements. By implementing low-cost GNSS technology, monitoring expenses can be reduced, facilitating the monitoring of more natural hazards and structures in the future. By employing low-cost dual-frequency GNSS instruments, we are progressively approaching the positioning quality level of geodetic GNSS instruments, which are significantly more expensive, ranging from twenty to forty times the cost.

• Language: English
• Keywords: Built environment, geodesy, doctoral thesis, GNSS, low-cost GNSS instruments, displacements, monitoring
• Work type: Doctoral dissertation
• Typology: 2.08 - Doctoral Dissertation
• Organization: FGG - Faculty of Civil and Geodetic Engineering
• Place of publishing: Ljubljana
• Publisher: [V. Hamza]
• Year: 2023
• Number of pages: XX, 83 str., [95] str. pril.
• PID: 20.500.12556/RUL-150505-65c42e33-727b-6c4d-d00c-53e889ac9a33
• UDC: 528.5:629.056.8:338.532.423(043.3)
• COBISS.SI-ID: 165748483
• Publication date in RUL: 20.09.2023

Secondary language

• Language: Slovenian
• Title: Uporaba cenovno ugodnih sprejemnikov GNSS za geodetski monitoring : doktorska disertacija

Abstract

Za spremljanje premikov in deformacij naravnih in antropogenih objektov se že vrsto let uporabljajo različne geodetske merske tehnike in senzorji. Med vsemi so se inštrumenti GNSS skozi leta izkazali za ustrezne pri geodetskem monitoringu, predvsem zaradi zmožosti zagotavljanja neprekinjene informacije o položaju z visoko točnostjo. Geodetski inštrumenti GNSS pa se v primerih, ko lahko pride do njihovih poškodb, izkažejo za cenovno neustrezne (lahko stanejo tudi nekaj 10.000 €), predvsem takrat, ko je potreba po večjem številu vzpostavljenih inštrumentov GNSS in lahko znesek preseže sto tisoč evrov. V takih primerih nam cenovno ugodni inštrumenti GNSS predstavljajo ustrezno alternativo kakovostnim, a dražjim, inštrumentom GNSS. Cenovno ugodni dvo-frekvenčni inštrumenti GNSS so prišli na trg leta 2019 in so zelo hitro pritegnili pozornost številnih raziskav v geodetski znanosti. Dvo-frekvenčni inštrumenti lahko sprejemajo signal na dveh nosilnih valovanjih GNSS, s čimer je možno v večini odpraviti pogrešek ionosfere, zato se je njihova uporabnost povečala v številnih aplikacijah. Cenovno ugodni inštrumenti GNSS imaju vgrajene tudi module RTK in se lahko uporabljajo v kombinaciji z geodetskimi antenami GNSS, zato so postali združljivi in primerljivi z visokokakovostnimi geodetskimi inštrumenti GNSS. Rezultati, prikazani v pričujočem delu, kažejo, da cenovno ugodni inštrumenti GNSS še ne zagotavljajo rezultatov z isto kakovostjo kot geodetski inštrumenti GNSS, ampak z nižjo. Kljub temu pa lahko ti senzorji določijo položaj s točnostjo, ki je sprejemljiva pri številnih nalogah geodetske izmere. Cenovno ugodne inštrumente GNSS smo uporabili za izgradnjo cenovno ugodnega kontrolnega sistema GNSS (angl. low-cost GNSS monitoring system – LGMS) pri nalogah geodetskega monitoringa. LGMS se je izkazal za ustrezno rešitev za neprekinjen nadzor stabilnosti z visoko točnostjo v skoraj realnem času in optimiziranimi stroški vzpostavitve ter delovanja. Izdelan LGMS smo uporabili na primeru plazu Laze, kjer smo izmero izvajali pol leta, a lahko sistem uporabimo za kontrolo stabilnosti poljubnega antropogenega (viadukti, mostovi, jezovi, območja rudarjenja, dimnikov in podobno) ali naravnega objekta (posedanja ali plazovi), če so pričakovani premiki ustrezno veliki. Zaradi globalnega segrevanja ozračja, se v prihodnosti pričakuje večje in močnejše padavine po vsem svetu, kar lahko vpliva na večje aktivnosti plazov in s tem na povečano potrebo po nadzoru le-teh. Uporaba cenovno ugodnih inštrumentov GNSS bo bistveno znižala stroške monitoringa in s tem povzročila možnost večjega in pogostejšega nadzora nad stabilnostjo naravnih kot tudi antropogenih objektov. Z uporabo cenovno ugodnih več-frekvenčnih inštrumentov GNSS se v sedanjem času že zelo bližamo kakovosti rezultatov, ki jih zagotavljajo visokokakovstni inštrumenti GNSS, a z močno znižanimi stroški vzpostavitve.

• Keywords: Grajeno okolje, geodezija, disertacije, GNSS, cenovno ugodni GNSS inštrumenti, premiki