Nowadays, with the incursion of low-cost GNSS receivers with modern characteristics, it is common to investigate and apply new methodologies and solutions with different receivers of this nature. Based on this fact, the performance of the solution obtained from the low-cost GNSS receiver is evaluated compared to a geodetic grade GNSS receiver at different sampling frequencies for the PPP-static and PPP-kinematic modes. For this, the original RINEX observation files were analyzed and decimated into different sampling rates as 0.1, 0.2, 1, 5, 15 and 30 s with TEQC software. All RINEX files were submitted to the Canadian Spatial Reference System Precise Point Positioning (CSRS-PPP) online service for processing with static and kinematic modes. The PPP-derived coordinates from the low-cost GNSS receiver were compared with the geodetic receiver to evaluate the obtained solution. The results reveal that the behavior of all studied sampling rates from the low-cost GNSS receiver are constant in achieved positioning. In addition, the achieved precision shows that it is recommendable to use a high sampling rate to obtain a cm level in PPP-static mode by using a low-cost GNSS receiver, this mode being the most accurate and potential alternative for structural health monitoring studies, mapping and positioning in urban areas.

A positional accuracy obtained by the Precise Point Positioning and static relative methods was compared and analyzed. Test data was collected using low-cost GNSS receivers of single- and dual-frequency in urban areas. The data was analyzed for quality using the TEQC program to determine the degree of affectation of the signal in the urban area. Low-cost GNSS receivers were found to be sensitive to the multipath effect, which impacts positioning. The horizontal and vertical accuracy was evaluated with respect to Mexican regulations for the GNSS establishment criteria. Probable Error Circle (CEP) and Vertical Positioning Accuracy (EPV) were performed on low cost GNSS receiver observation data. The results show that low-cost dual-frequency GNSS receivers can be used in urban areas. The precision was obtained in the order of 0.013 m in the static relative method. The results obtained are comparable to a geodetic receiver in a geodetic baseline of <20 km. The study does not recommend using single and dual frequencies low cost GNSS receivers based on results obtained by the Precise Point Positioning (PPP) method in urban areas. The inclusion of the GGM10 model reduces the vertical precision obtained by using low cost GNSS receivers in both methods, conforming to the regulations only in the horizontal component.

As everywhere in the Andes, tropical glaciers have been rapidly retreating since several decades. The glaciers of Cotopaxi volcano, Ecuador, have been reduced in area by about 50% since 1976 (Cáceres, 2017). The Cotopaxi is mostly famous for its capacity to produce massive lahars during volcanic eruptions, but comparably smaller, secondary lahars generated in post-eruptive periods by heavy rainfall occur more frequently on the volcano’s flanks. However, since a few years, secondary lahars that originate in proglacial areas without any clear trigger mechanism are recorded at Cotopaxi. This raises the question of whether there exists a process-based link between the occurrence of secondary lahars and the retreat of cold-based glaciers with accompanied permafrost degradation in the former subglacial frozen pyroclastic material over the following years and decades.Here, we present the data obtained from laboratory-calibrated Electrical Resistivity Tomography (ERT) and Seismic Refraction Tomography (SRT) conducted near the glacier margin between 5000 and 5300 m asl, which provide a better understanding of frozen/unfrozen conditions and the structure of the subsurface. In addition, data loggers have been recording surface air temperatures close to the glacier since May 2018. Our measurements show that permafrost cannot develop under current thermal conditions, but high electrical resistivities at depths of 10-20 m correspond to calibrated rock temperatures below 0 °C. The detected frozen lenses may act as detachment planes of periglacial secondary lahars in pyroclastic material recently exposed by glacier retreat. Cáceres, B. (2017). Goal workshop 2017 Mexico 135 Evolución de los glaciares del Ecuador durante los últimos 60 años y su relación con el cambio climático. Conference paper: The role of Geosciences to societal development: A German-Latin American Perspective. GOAL Geo-Network of Latin American-German Alumini. P. 149. México: UANL-Monterrey-México.

Emerging low-cost Global Navigation Satellite System (GNSS) receivers are gaining prominence in geosciences and surveying engineering, finding application in diverse positioning research endeavors. The primary aim of this study was to assess the structural integrity using low-cost GNSS technology, whose usability has advanced significantly. The fundamental premise of the research is the assumption that the lifespan of the dam has reached its end in accordance with international regulations. Over a span of four years and across multiple campaigns, a combination of low-cost GNSS, high precision leveling data, and Finite Element Modeling techniques were employed to monitor deformations at the Sanalona dam. A notable deformation was identified at the central curtain of the dam. Utilizing low-cost GNSS equipment, horizontal deformations of up to 10 cm and vertical deformations of up to 30 cm were recorded. These values do not jeopardize the operational objectives of the dam as per the stipulations of the U.S. Army Corps of Engineers (USACE). The Sanalona Dam continues to operate effectively within the bounds of international regulations, even when subjected to extraordinary phenomena. The findings of this study hold relevance for the wider adoption of low-cost GNSS equipment in civil engineering structures and other demanding geodetic applications, including historic infrastructures. Moreover, the study underscores the viability of conducting precise dam surveys utilizing low-cost GNSS devices in campaign mode.