scholarly journals Snow Depth Estimation with GNSS-R Dual Receiver Observation

2019 ◽  
Vol 11 (17) ◽  
pp. 2056 ◽  
Author(s):  
Yu ◽  
Wang ◽  
Li ◽  
Chang ◽  
Li
Keyword(s):  
Snow Depth ◽  
Carrier Phase ◽  
Mean Squared Error ◽  
Depth Estimation ◽  
Combination Method ◽  
Estimation Methods ◽  
Single Frequency ◽  
Dual Frequency ◽  
Combination Methods ◽  
Receiver System

Two estimation methods using a dual GNSS (Global Navigation Satellite System) receiver system are proposed. The dual-frequency combination method combines the carrier phase observations of dual-frequency signals, whereas the single-frequency combination method combines the pseudorange and carrier phase observations of a single-frequency signal, both of which are geometry-free strictly combination and free of the effect of ionospheric delay. Theoretical models are established in the offline phase to describe the relationship between the spectral peak frequency of the combined sequence and the antenna height. A field experiment was conducted recently and the data processing results show that the root mean squared error (RMSE) of the dual-frequency combination method is 5.04 cm with GPS signals and 6.26 cm with BDS signals, which are slightly greater than the RMSE of 4.16 cm produced by the single-frequency combination method of L1 band with GPS signals. The results also demonstrate that the proposed two combination methods and the SNR method achieve similar performance. A dual receiver system enables the better use of GNSS signal carrier phase observations for snow depth estimation, achieving increased data utilization.

scholarly journals Comparison of Multi-GNSS Time and Frequency Transfer Performance Using Overlap-Frequency Observations

2021 ◽  
Vol 13 (16) ◽  
pp. 3130
Author(s):  
Pengfei Zhang ◽  
Rui Tu ◽  
Yuping Gao ◽  
Ju Hong ◽  
Junqiang Han ◽  
...  
Keyword(s):  
Carrier Phase ◽  
Satellite System ◽  
Single Frequency ◽  
Navigation Satellite ◽  
Transfer Performance ◽  
Dual Frequency ◽  
Time Transfer ◽  
Difference Series ◽  
Frequency Transfer ◽  
Global Navigation Satellite

The modernized GPS, Galileo, and BeiDou global navigation satellite system (BDS3) offers new potential for time transfer using overlap-frequency (L1/E1/B1, L5/E5a/B2a) observations. To assess the performance of time and frequency transfer with overlap-frequency observations for GPS, Galileo, and BDS3, the mathematical models of single- and dual-frequency using the carrier-phase (CP) technique are discussed and presented. For the single-frequency CP model, the three-day average RMS values of the L5/E5a/B2a clock difference series were 0.218 ns for Galileo and 0.263 ns for BDS3, of which the improvements were 36.2% for Galileo and 43.9% for BDS3 when compared with the L1/E1/B1 solution at BRUX–PTBB. For the hydrogen–cesium time link BRUX–KIRU, the RMS values of the L5/E5a/B2a solution were 0.490 ns for Galileo and 0.608 ns for BDS3, improving Galileo by 6.4% and BDS3 by 12.5% when compared with the L1/E1/B1 solution. For the dual-frequency CP model, the average stability values of the L5/E5a/B2a solution at the BRUX–PTBB time link were 3.54∙× 10−12 for GPS, 2.20 × 10−12 for Galileo, and 2.69 × 10−12 for BDS3, of which the improvements were 21.0%, 45.1%, and 52.3%, respectively, when compared with the L1/E1/B1 solution. For the BRUX–KIRU time link, the improvements were 4.2%, 30.5%, and 36.1%, respectively.

scholarly journals Impact of UAS Image Orientation on Accuracy of Forest Inventory Attributes

2020 ◽  
Vol 12 (3) ◽  
pp. 404 ◽  
Author(s):  
Luka Jurjević ◽  
Mateo Gašparović ◽  
Anita Simic Milas ◽  
Ivan Balenović
Keyword(s):  
Carrier Phase ◽  
Single Frequency ◽  
Pedunculate Oak ◽  
Dual Frequency ◽  
3D Point Clouds ◽  
Sensor Orientation ◽  
Forested Areas ◽  
Gnss Measurements ◽  
Image Orientation ◽  
Gnss Data

The quality and accuracy of Unmanned Aerial System (UAS) products greatly depend on the methods used to define image orientations before they are used to create 3D point clouds. While most studies were conducted in non- or partially-forested areas, a limited number of studies have evaluated the spatial accuracy of UAS products derived by using different image block orientation methods in forested areas. In this study, three image orientation methods were used and compared: (a) the Indirect Sensor Orientation (InSO) method with five irregularly distributed Ground Control Points (GCPs); (b) the Global Navigation Satellite System supported Sensor Orientation (GNSS-SO) method using non-Post-Processed Kinematic (PPK) single-frequency carrier-phase GNSS data (GNSS-SO1); and (c) using PPK dual-frequency carrier-phase GNSS data (GNSS-SO2). The effect of the three methods on the accuracy of plot-level estimates of Lorey’s mean height (HL) was tested over the mixed, even-aged pedunculate oak forests of Pokupsko basin located in Central Croatia, and validated using field validation across independent sample plots (HV), and leave-one-out cross-validation (LOOCV). The GNSS-SO2 method produced the HL estimates of the highest accuracy (RMSE%: HV = 5.18%, LOOCV = 4.06%), followed by the GNSS-SO1 method (RMSE%: HV = 5.34%, LOOCV = 4.37%), while the lowest accuracy was achieved by the InSO method (RMSE%: HV = 5.55%, LOOCV = 4.84%). The negligible differences in the performances of the regression models suggested that the selected image orientation methods had no considerable effect on the estimation of HL. The GCPs, as well as the high image overlaps, contributed considerably to the block stability and accuracy of image orientation in the InSO method. Additional slight improvements were achieved by replacing single-frequency GNSS measurements with dual-frequency GNSS measurements and by incorporating PPK into the GNSS-SO2 method.

scholarly journals Carrier Phase-Based Precise Heading and Pitch Estimation Using a Low-Cost GNSS Receiver

2021 ◽  
Vol 13 (18) ◽  
pp. 3642
Author(s):  
Wei Ding ◽  
Wei Sun ◽  
Yang Gao ◽  
Jiaji Wu
Keyword(s):  
Carrier Phase ◽  
Measurement Errors ◽  
Low Cost ◽  
Installation Space ◽  
Estimation Methods ◽  
Single Frequency ◽  
Cycle Slip ◽  
Pitch Estimation ◽  
Gnss Receiver ◽  
Mean Square Errors

Attitude and heading estimation methods using the global navigation satellite system (GNSS) are generally based on multi-antenna deployment, where the installation space and system cost increase with the increase in the number of antennas. Since the single-antenna receiver is still the major choice of the mass market, we focus on precise and reliable heading and pitch estimation using a low-cost GNSS receiver. Carrier phase observations are precise but have an ambiguity problem. A single difference between consecutive epochs can eliminate ambiguity and reduce the measurement errors. In this work, a measurement model based on the time-differenced carrier phases (TDCPs) is utilized to estimate the precise delta position of the antenna between two consecutive epochs. Then, considering the motion constraint, the heading and pitch angles of a moving land vehicle can be determined by the components of the estimated receiver delta position. A threshold on the length of the delta position is selected to avoid large errors in static periods. To improve the reliability of the algorithm, the Doppler-aided cycle slip detection method is applied to exclude carrier phases with possible cycle slips. A real vehicular dynamic experiment using a low-cost, single-frequency GNSS receiver is conducted to evaluate the proposed algorithm. The experimental results show that the proposed algorithm is capable of providing precise vehicular heading and pitch estimates, with both the root mean square errors being better than 1.5°. This also indicates that the cycle slip exclusion is indispensable to avoid unexpected large errors.

Estimation of snow depth using pseudorange and carrier phase observations of GNSS single-frequency signal

GPS Solutions ◽  
2019 ◽  
Vol 23 (4) ◽  
Author(s):  
Yunwei Li ◽  
Xin Chang ◽  
Kegen Yu ◽  
Shuyao Wang ◽  
Jiancheng Li
Keyword(s):  
Snow Depth ◽  
Carrier Phase ◽  
Single Frequency ◽  
Frequency Signal

scholarly journals Depth estimation for a road scene using a monocular image sequence based on fully convolutional neural network

2020 ◽  
Vol 17 (3) ◽  
pp. 172988142092530
Author(s):  
Haixia Wang ◽  
Yehao Sun ◽  
Zhiguo Zhang ◽  
Xiao Lu ◽  
Chunyang Sheng
Keyword(s):  
Neural Network ◽  
Convolutional Neural Network ◽  
Evaluation Method ◽  
Mean Squared Error ◽  
Input Sequence ◽  
Depth Estimation ◽  
Estimation Methods ◽  
Convolutional Network ◽  
Regression Problem ◽  
Depth Prediction

An advanced driving assistant system is one of the most popular topics nowadays, and depth estimation is an important cue for advanced driving assistant system. Depth prediction is a key problem in understanding the geometry of a road scene for advanced driving assistant system. In comparison to other depth estimation methods using stereo depth perception, determining depth relation using a monocular camera is considerably challenging. In this article, a fully convolutional neural network with skip connection based on a monocular video sequence is proposed. With the integration framework that combines skip connection, fully convolutional network and the consistency between consecutive frames of the input sequence, high-resolution depth maps are obtained with lightweight network training and fewer computations. The proposed method models depth estimation as a regression problem and trains the proposed network using a scale invariance optimization based on L2 loss function, which measures the relationships between points in the consecutive frames. The proposed method can be used for depth estimation of a road scene without the need for any extra information or geometric priors. Experiments on road scene data sets demonstrate that the proposed approach outperforms previous methods for monocular depth estimation in dynamic scenes. Compared with the currently proposed method, our method has achieved good results when using the Eigen split evaluation method. The obvious prominent one is that the linear root mean squared error result is 3.462 and the δ < 1.25 result is 0.892.

scholarly journals A Tale of Five Bridges; the use of GNSS for Monitoring the Deflections of Bridges

2014 ◽  
Vol 8 (4) ◽  
Author(s):  
Gethin Wyn Roberts ◽  
Christopher J. Brown ◽  
Xu Tang ◽  
Xiaolin Meng ◽  
Oluropo Ogundipe
Keyword(s):  
Carrier Phase ◽  
Suspension Bridge ◽  
Single Frequency ◽  
Gps Data ◽  
Dual Frequency ◽  
Bridge Monitoring ◽  
Gnss Receivers ◽  
Rtk Gps ◽  
Millennium Bridge ◽  
Gathering Data

AbstractThe first Bridge Monitoring surveying was carried out in 1996 by the authors, through attaching Ashtech ZXII GPS receivers onto the Humber Bridge’ parapet, and gathering and further analysing the resulting 1 Hz RTK GPS data. Various surveys have subsequently been conducted on the Humber Bridge, the Millennium Bridge, the Forth Road Bridge, the Severn Suspension Bridge and the Avonmouth Viaduct. These were all carried out using survey grade carrier phase/pseudorange GPS and later GNSS receivers. These receivers were primarily dual frequency receivers, but the work has also investigated the use of single frequency receivers, gathering data at 1 Hz, 10 Hz, 20 Hz and even 100 Hz. Various aspects of the research conducted are reported here, as well as the historical approach. Conclusions are shown in the paper, as well as lessons learnt during the development of this work. The results are compared to various models that exist of the bridges’ movements, and compare well. The results also illustrate that calculating the frequencies of the movements, as well as looking at the magnitudes of the movements, is an important aspect of this work. It is also shown that in instances where the magnitudes of the movements of the bridge under investigation are small, it is still possible to derive very accurate frequencies of the movements, in comparison to the existing models.

Impact of New GPS Signals on Positioning Accuracy for Urban Bus Operations

2020 ◽  
Vol 73 (6) ◽  
pp. 1284-1305
Author(s):  
Mireille Elhajj ◽  
Washington Ochieng
Keyword(s):  
Carrier Phase ◽  
Signal To Noise Ratio ◽  
Three Dimensional ◽  
Dimensional Accuracy ◽  
Single Frequency ◽  
Measurement Unit ◽  
Dual Frequency ◽  
Positioning Accuracy ◽  
Phase Measurements ◽  
The Impact

This paper analyses for the first time the impact of new GPS signals on positioning accuracy for dynamic urban applications, taking bus operations as an example. The performance assessment addresses both code measurement precision and positioning accuracy. The former is based on signal-to-noise ratio and estimation of multipath and noise by a combination of code and carrier phase measurements. The impact on positioning accuracy is derived by comparing the performance achievable with the conventional single frequency GPS only positioning both relative to reference trajectories from the integration of carrier phase measurements with data from a high grade inertial measurement unit. The results show that L5 code measurements have the highest precision, followed by L1 C/A and L2C. In the positioning domain, there is a significant improvement in two-dimensional and three-dimensional accuracy from dual frequency code measurements over the single frequency measurements, of 39% and 48% respectively, enabling more bus operation services to be supported.

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