Limits on GNSS Performance at High Latitudes

Swaszek, Peter F.; Hartnett, Richard J.; Seals, Kelly C.; Siciliano, Joseph D.; Swaszek, Rebecca M. A.

doi:10.33012/2018.15549

Cited by 3 publications

(4 citation statements)

References 8 publications

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“…For the single flight undertaken on the 15th, there appears to be consistent negative offset compared to all other flights undertaken during the survey period, with a median offset of -0.152--0.248 m when compared to F1 on the 8th and both flights on the 9th, for which there may be several potential causes. A likely prominent cause of this error is positional postprocessing, where resolving accuracy in the Z direction is traditionally most complex, with errors in the range of decimetres common, especially at high latitudes where there are no-satellite zones in the sky and the majority of satellites are close to the horizon (Hugenholtz et al, 2016;Swaszek et al, 2018). This is particularly important as a reduction in the number of satellites positioned high above the horizon reduces the ability for a receiver to determine its position, especially in the Z direction (Karaim et al, 2018;Swaszek et al, 2018).…”

Section: Data Quality Assessmentmentioning

confidence: 99%

“…A likely prominent cause of this error is positional postprocessing, where resolving accuracy in the Z direction is traditionally most complex, with errors in the range of decimetres common, especially at high latitudes where there are no-satellite zones in the sky and the majority of satellites are close to the horizon (Hugenholtz et al, 2016;Swaszek et al, 2018). This is particularly important as a reduction in the number of satellites positioned high above the horizon reduces the ability for a receiver to determine its position, especially in the Z direction (Karaim et al, 2018;Swaszek et al, 2018). Figure 4 shows the difference in satellite locations and elevations relative to the study site for the 9th and 15th July.…”

Section: Data Quality Assessmentmentioning

confidence: 99%

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Assessing UAV-based laser scanning for monitoring glacial processes and interactions at high spatial and temporal resolutions

Baurley

Tomsett

Hart

2022

Front. Remote Sens.

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Uncrewed Aerial Vehicles (UAVs), in combination with Structure from Motion (SfM) photogrammetry, have become an established tool for reconstructing glacial and ice-marginal topography, yet the method is highly dependent on several factors, all of which can be highly variable in glacial environments. However, recent technological advancements, related primarily to the miniaturisation of new payloads such as compact Laser Scanners (LS), has provided potential new opportunities for cryospheric investigation. Indeed, UAV-LS systems have shown promise in forestry, river, and snow depth research, but to date the method has yet to be deployed in glacial settings. As such, in this study we assessed the suitability of UAV-LS for glacial research by investigating short-term changes in ice surface elevation, calving front geometry and crevasse morphology over the near-terminus region of an actively calving glacier in southeast Iceland. We undertook repeat surveys over a 0.1 km2 region of the glacier at sub-daily, daily, and weekly temporal intervals, producing directly georeferenced point clouds at very high spatial resolutions (average of >300 points per m−2 at 40 m flying height). Our data has enabled us to: 1) Accurately map surface elevation changes (Median errors under 0.1 m), 2) Reconstruct the geometry and evolution of an active calving front, 3) Produce more accurate estimates of the volume of ice lost through calving, and 4) Better detect surface crevasse morphology, providing future scope to extract size, depth and improve the monitoring of their evolution through time. We also compared our results to data obtained in parallel using UAV-SfM, which further emphasised the relative advantages of our method and suitability in glaciology. Consequently, our study highlights the potential of UAV-LS in glacial research, particularly for investigating glacier mass balance, changing ice dynamics, and calving glacier behaviour, and thus we suggest it has a significant role in advancing our knowledge of, and ability to monitor, rapidly changing glacial environments in future.

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Section: Data Quality Assessmentmentioning

confidence: 99%

Section: Data Quality Assessmentmentioning

confidence: 99%

Assessing UAV-based laser scanning for monitoring glacial processes and interactions at high spatial and temporal resolutions

Baurley

Tomsett

Hart

2022

Front. Remote Sens.

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“…The goal of this study was to extend previous analyses by assessing the demodulation performance of the Galileo E6B signal. The focus of this work is on high-latitude conditions where satellite visibility may be partially reduced [10]. A professional Septentrio PolaRx5S was installed on a Hurtigruten vessel operating in the Norwegian Sea and reaching latitudes exceeding 71 degrees North.…”

Section: Introductionmentioning

confidence: 99%

“…A professional Septentrio PolaRx5S was installed on a Hurtigruten vessel operating in the Norwegian Sea and reaching latitudes exceeding 71 degrees North. At these latitudes, the Position Dilution Of Precision (PDOP) can be reduced, as discussed in [10,11]. Moreover, adverse ionospheric conditions [12][13][14] can further degrade receiver performance, reducing demodulation capabilities.…”

Section: Introductionmentioning

confidence: 99%

Assessment of Galileo E6B Data Demodulation Performance at High Latitudes: A Norwegian Vessel Case Study

et al. 2021

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The Galileo High Accuracy Service (HAS) is currently in its testing phase, in which actual corrections are transmitted along with standard dummy messages. The dissemination of Precise Point Positioning (PPP) corrections is performed using an innovative scheme based on a Reed–Solomon code, which allows the reconstruction of the original navigation message from a subset of received pages. This approach introduces robustness to the reception process and aims at reducing the Time-to-Retrieve Data (TTRD); that is, the time to retrieve the HAS message. This study investigated the HAS demodulation performance considering Galileo signals collected at high latitudes. In particular, a Galileo E6-capable receiver was mounted on a vessel sailing from Bergen to Kirkenes, Norway, and reaching up to 71 degrees North. The trajectory of the vessel was at the border of the Galileo HAS service area and high-latitudes impact reception conditions, potentially leading to poor satellite geometries. Three months of data from January to March 2021 were analyzed, considering several metrics including Bit Error Rate (BER), Page Error Rate (PER), and TTRD. The analysis shows that the Reed–Solomon scheme adopted for data dissemination is also effective at high-latitudes, with daily PER below one percent and mean TTRD in the order of eight seconds when three satellites are broadcasting valid HAS corrections. Lower values of the TTRD are achieved with an increased number of satellites. These values are significantly lower than the update rate of the corrections broadcast by the Galileo HAS.

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Characterization of the precision of PPP solutions as a function of latitude and session length

Kurtz,

Gómez,

Bevis

2024

Journal of Geodetic Science

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This study investigates the impact of observation session duration and station latitude on the precision of Precise Point Positioning (PPP). Global Positioning System-only Receiver Independent Exchange files from 516 continuous stations spanning latitudes from 90°N to 90°S across the Americas (30°–130°W) were binned into sessions of 1, 2, 3, 4, 6, and 12 h and processed using the GPSPACE PPP software. These sub-daily solutions, along with the original 24 h ones, were compared against a reference coordinate derived from an extended linear trajectory model for each station. Analysis of the results, considering both accuracy and precision, was conducted across the entire latitude range of the study. We found that the precision of a PPP solution approximately follows a power-law relationship with observation duration. Parameters for these power-law relationships were determined for all latitude ranges that allow users to predict a result’s uncertainty as a function of session length. Findings indicate that longer observation sessions lead to reduced positioning errors, with vertical scatter decreasing with increasing latitude. Since all these stations are characterized by good to excellent sky view, our power-law rule-of-thumb provides a lower bound on the occupation time needed to achieve target positioning precision at locations with poorer sky visibility.

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Limits on GNSS Performance at High Latitudes

Abstract: Coast Guard Academy, having retired from the USCG as a Captain in 2009. His research interests include efficient digital filtering methods, improved receiver signal processing techniques for electronic navigation systems, and autonomous vehicle design.

Cited by 3 publications

References 8 publications

Assessing UAV-based laser scanning for monitoring glacial processes and interactions at high spatial and temporal resolutions

Assessing UAV-based laser scanning for monitoring glacial processes and interactions at high spatial and temporal resolutions

Assessment of Galileo E6B Data Demodulation Performance at High Latitudes: A Norwegian Vessel Case Study

Characterization of the precision of PPP solutions as a function of latitude and session length

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