scholarly journals Impact of Approximate Implementation manner in Klobuchar Model

2021 ◽  
Vol 64 (4) ◽  
pp. RS440
Author(s):  
Aghyas Aljuneidi ◽  
Hala Tawfek Hasan
Keyword(s):  
Single Frequency ◽  
Gps Receiver ◽  
Reference Field ◽  
International Geomagnetic Reference Field ◽  
Ionospheric Correction ◽  
Correction Model ◽  
Klobuchar Model ◽  
Magnetic Model ◽  
Implementation In Matlab ◽  
Made In

This paper focuses on the approximations that John A. Klobuchar made in mid 70s in his famous algorithm of ionospheric correction model for single frequency GPS receiver. At that time Klobuchar used a system of fixed geomagnetic north pole coordinates which are not accurate nowadays according to the International Geomagnetic Reference Field and to the World Magnetic Model because the geomagnetic poles move slowly. In addition, Klobuchar had to do other trigonometry simplifications in his implementation to avoid sophisticated computations. In order to evaluate this approximate implementation in a single frequency GPS receiver, ionospheric time and range delay are estimated on the entire day of January 1st 2010, using a different implementation in MATLAB. The required GPS data is obtained from recorded RINEX files at UDMC near DAMASCUS, SYRIA. In this comparative study, we reformulated the standard equations of Klobuchar model and examined the influence of its approximations on the ionospheric range delay and found a non- negligible bias in order of ten centimeters, whereas the influence of the movement of the geomagnetic poles was in order of few centimeters.

scholarly journals Assessment and Comparison of Broadcast Ionospheric Models: NTCM-BC, BDGIM, and Klobuchar

2020 ◽  
Vol 12 (7) ◽  
pp. 1215 ◽  
Author(s):  
Chao Yang ◽  
Jing Guo ◽  
Tao Geng ◽  
Qile Zhao ◽  
Kecai Jiang ◽  
...  
Keyword(s):  
Ionospheric Delay ◽  
Global Navigation Satellite Systems ◽  
Single Frequency ◽  
Electron Content ◽  
Ionospheric Correction ◽  
Total Electron ◽  
Correction Model ◽  
Satellite Systems ◽  
Satellite Navigation System ◽  
Navigation Data

For single-frequency Global Navigation Satellite Systems (GNSSs) users, ionospheric delay is the main error source affecting the accuracy of positioning. Applying a broadcast ionospheric correction model to mitigate the ionospheric delay is essential for meter-to-decimeter-level accuracy positioning. To provide support for real-time single-frequency operations, particularly in the China area, we assessed the performance of three broadcast ionospheric correction models, namely, the Neustrelitz total electron content (TEC) broadcast model (NTCM-BC), the BeiDou global broadcast ionospheric delay correction model (BDGIM), and the Klobuchar model. In this study, the broadcast coefficients of Klobuchar and BDGIM are obtained from the navigation data files directly. Two sets of coefficients of NTCM-BC for China and global areas are estimated. The slant total electron contents (STEC) data from more than 80 validation stations and the final vertical TEC (VTEC) data of the Center for Orbit Determination in Europe (CODE) are used as independent benchmarks for comparison. Compared to GPS STEC during the period of Day of Year (DOY) 101~199, 2019, the ionospheric correction ratio of NTCM-BC, BDGIM, and Klobuchar are 79.4%, 64.9%, and 57.7% in China, respectively. For the global area, the root-mean-square (RMS) errors of these three models are 3.67 TECU (1 TECU = 1016 electrons/m2), 5.48 TECU, and 8.92 TECU, respectively. Compared to CODE VTEC in the same period, NTCM-BC, BDGIM, and Klobuchar can correct 72.6%, 69.8%, and 61.7% of ionospheric delay, respectively. Hence, NTCM-BC is recommended for use as the broadcast ionospheric model for the new-generation BeiDou satellite navigation system (BDS) and its satellite-based augmentation system.

scholarly journals Positioning performance of the NTCM model driven by GPS Klobuchar model parameters

2018 ◽  
Vol 8 ◽  
pp. A20 ◽  
Author(s):  
Mohammed Mainul Hoque ◽  
Norbert Jakowski ◽  
Jens Berdermann
Keyword(s):  
Single Frequency ◽  
Activity Period ◽  
Model Parameters ◽  
Signal Delay ◽  
Correction Algorithm ◽  
Ionospheric Correction ◽  
Model Driven ◽  
Position Errors ◽  
Klobuchar Model ◽  
Range Error

Users of the Global Positioning System (GPS) utilize the Ionospheric Correction Algorithm (ICA) also known as Klobuchar model for correcting ionospheric signal delay or range error. Recently, we developed an ionosphere correction algorithm called NTCM-Klobpar model for single frequency GNSS applications. The model is driven by a parameter computed from GPS Klobuchar model and consecutively can be used instead of the GPS Klobuchar model for ionospheric corrections. In the presented work we compare the positioning solutions obtained using NTCM-Klobpar with those using the Klobuchar model. Our investigation using worldwide ground GPS data from a quiet and a perturbed ionospheric and geomagnetic activity period of 17 days each shows that the 24-hour prediction performance of the NTCM-Klobpar is better than the GPS Klobuchar model in global average. The root mean squared deviation of the 3D position errors are found to be about 0.24 and 0.45 m less for the NTCM-Klobpar compared to the GPS Klobuchar model during quiet and perturbed condition, respectively. The presented algorithm has the potential to continuously improve the accuracy of GPS single frequency mass market devices with only little software modification.

scholarly journals The new WMM2020 and IGRF-13 models, and a retrospective analysis of IGRF secular variation

2020 ◽  
Author(s):  
William Brown ◽  
Ciarán Beggan ◽  
Grace Cox ◽  
Susan Macmillan
Keyword(s):  
Retrospective Analysis ◽  
Secular Variation ◽  
Task Force ◽  
Reference Field ◽  
Coordinate Systems ◽  
International Geomagnetic Reference Field ◽  
The North ◽  
The Us ◽  
The World ◽  
Magnetic Model

<p>2020 marks the start of a new 5-year cycle and updated releases of the World Magnetic Model (WMM) and International Geomagnetic Reference Field (IGRF). These models provide a reference for the up-to-date internal geomagnetic field in 2020, and a prediction of its secular variation for the next 5 years, to 2025. While similar in some aspects, the two models have different specifications and many different users across diverse fields. They provide references to be used primarily for navigation (WMM) and geomagnetic coordinate systems (IGRF).</p><p>BGS produces the WMM in collaboration with the US’ NOAA/NCEI, while the IGRF is produced by an IAGA Div. V-MOD task force, this time consisting of fifteen teams across nine nations, including BGS. Here we present a summary of the production of the updated WMM2020 and IGRF-13, and BGS efforts to enable access to these models.</p><p>We also present a retrospective analysis of the predictive components of the candidate models for previous IGRF epoch’s secular variation. Recent epochs have seen notable geomagnetic jerks and the acceleration of the North magnetic dip pole, features not well represented by the constant SV format of models such as the IGRF. We assess the range of candidate models submitted for previous IGRF epochs, assess the accuracy of physically derived predictions versus mathematical extrapolations, and discuss the implications given the range of candidate models submitted for IGRF-13 secular variation over the next five years.</p>

scholarly journals Improvement and Validation of Ranging Accuracy with YG-13A

2017 ◽  
Author(s):  
Mingjun Deng ◽  
Guo Zhang ◽  
Ruishan Zhao ◽  
Jiansong Li ◽  
Jiansong Li
Keyword(s):  
Target Location ◽  
Single Frequency ◽  
Path Delay ◽  
Gps Receiver ◽  
Dual Frequency ◽  
Error Sources ◽  
Correction Model ◽  
Pixel Location ◽  
Atmospheric Path ◽  
Set Up

YG-13A represents the highest level of Chinese SAR satellites to date. In this paper, we report on experiments conducted to improve and validate ranging accuracy with YG-13A. We analyze the error sources in the YG-13A ranging system, such as atmospheric path delay, and transceiver channel delay. A real-time atmospheric delay correction model is established to calculate the atmospheric path delay, considering the troposphere delay and ionosphere delay. Six corner reflectors (CRs) were set up to ensure the accuracy of validation methods. Pixel location accuracies of up to 0.479-m standard deviation can be achieved after a complete calibration. We further demonstrate that the adjustment of the CRs can cause a marginal loss of ranging precision. After eliminating this error, the ranging accuracy is improved to 0.237 m. For YG-13A, a single frequency GPS receiver is used and the orbital nominal accuracy is 0.3 m, which is the biggest factor restricting its ranging accuracy. Our results show that the ranging accuracy of YG-13A can achieve decimeter-level, which is lower than centimeter-level accuracy with TerraSAR-X loading a dual frequency GPS. YG-13A has great convenience in terms of access to control points and target location that does not depend on ground equipment.

scholarly journals The 10th generation international geomagnetic reference field

2005 ◽  
Vol 151 (3-4) ◽  
pp. 320-322 ◽  
Author(s):  
S. Maus ◽  
S. Macmillan ◽  
T. Chernova ◽  
S. Choi ◽  
D. Dater ◽  
...  
Keyword(s):  
Reference Field ◽  
International Geomagnetic Reference Field ◽  
International Geomagnetic Reference
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