scholarly journals A brief description of the GPS architecture

2020 ◽  
pp. 12-16
Author(s):  
Paul Medina-Castro ◽  
Camilo Caraveo-Mena ◽  
Norma Alicia Barboza-Tello ◽  
Raúl Loredo-Medina
Keyword(s):  
Satellite System ◽  
Gps Receiver ◽  
Precise Timing ◽  
Gps System

The GPS is a radio-satellite system that allows to the GPS receiver to figure out its tridimensional position on the globe (latitude, longitude, and elevation), as well as allows it to determine its velocity and to make precise timing measurements. This article describes the architecture of the GPS system for the non- specialized reader. The objective is that the lector has an idea of all that happens when using some equipment or application based on this technology.

scholarly journals From GPS Receiver to GNSS Reflectometry Payload Development for the Triton Satellite Mission

2021 ◽  
Vol 13 (5) ◽  
pp. 999
Author(s):  
Yung-Fu Tsai ◽  
Wen-Hao Yeh ◽  
Jyh-Ching Juang ◽  
Dian-Syuan Yang ◽  
Chen-Tsung Lin
Keyword(s):  
Satellite System ◽  
Low Earth Orbit ◽  
Export Control ◽  
Navigation Systems ◽  
Gps Receiver ◽  
Design Development ◽  
Satellite Mission ◽  
Essential Components ◽  
Gnss Reflectometry ◽  
Global Navigation Satellite

The global positioning system (GPS) receiver has been one of the most important navigation systems for more than two decades. Although the GPS system was originally designed for near-Earth navigation, currently it is widely used in highly dynamic environments (such as low Earth orbit (LEO)). A space-capable GPS receiver (GPSR) is capable of providing timing and navigation information for spacecraft to determine the orbit and synchronize the onboard timing; therefore, it is one of the essential components of modern spacecraft. However, a space-grade GPSR is technology-sensitive and under export control. In order to overcome export control, the National Space Organization (NSPO) in Taiwan completed the development of a self-reliant space-grade GPSR in 2014. The NSPO GPSR, built in-house, has passed its qualification tests and is ready to fly onboard the Triton satellite. In addition to providing navigation, the GPS/global navigation satellite system (GNSS) is facilitated to many remote sensing missions, such as GNSS radio occultation (GNSS-RO) and GNSS reflectometry (GNSS-R). Based on the design of the NSPO GPSR, the NSPO is actively engaged in the development of the Triton program (a GNSS reflectometry mission). In a GNSS-R mission, the reflected signals are processed to form delay Doppler maps (DDMs) so that various properties (including ocean surface roughness, vegetation, soil moisture, and so on) can be retrieved. This paper describes not only the development of the NSPO GPSR but also the design, development, and special features of the Triton’s GNSS-R mission. Moreover, in order to verify the NSPO GNSS-R receiver, ground/flight tests are deemed essential. Then, data analyses of the airborne GNSS-R tests are presented in this paper.

scholarly journals Absolute Calibration or Validation of the Altimeters on the Sentinel-3A and the Jason-3 over Lake Issykkul (Kyrgyzstan)

2018 ◽  
Vol 10 (11) ◽  
pp. 1679 ◽  
Author(s):  
Jean-François Crétaux ◽  
Muriel Bergé-Nguyen ◽  
Stephane Calmant ◽  
Nurzat Jamangulova ◽  
Rysbek Satylkanov ◽  
...  
Keyword(s):  
Satellite System ◽  
Reference Points ◽  
Absolute Calibration ◽  
In Situ Data ◽  
Absolute Bias ◽  
Weather Stations ◽  
Field Campaigns ◽  
The Absolute ◽  
Gps System ◽  
Water Height

Calibration/Validation (C/V) studies using sites in the oceans have a long history and protocols are well established. Over lakes, C/V allows addressing problems such as the performance of the various retracking algorithms and evaluating the accuracy of the geophysical corrections for continental waters. This is achievable when measurements of specific and numerous field campaigns and a ground permanent network of level gauges and weather stations are processed. C/V consists of installation of permanent sites (weather stations, limnigraphs, and GPS reference points) and the organization of regular field campaigns. The lake Issykkul serves as permanent site of C/V, for a multi-mission purpose. The objective of this paper is to calculate the altimeter biases of Jason-3 and Sentinel-3A, both belonging to an operational satellite system which is used for the long-term monitoring of lake level variations. We have also determined the accuracy of the altimeters of these two satellites, through a comparison analysis with in situ data. In 2016 and 2017, three campaigns have been organized over this lake in order to estimate the absolute bias of the nadir altimeter onboard the Jason-3 and Sentinel-3A. The fieldwork consisted of measuring water height using a GPS system, carried on a boat, along the track of the altimeter satellite across the lake. It was performed at the time of the pass of the altimeter. Absolute altimeter biases were calculated by averaging the water height differences along the pass of the satellite (GPS from the boat system versus altimetry). Jason-3 operates in a Low Resolution Mode (LRM), while the Sentinel-3A operates in Synthetic Aperture Radar (SAR) mode. In this study we found that the absolute biases measured for Jason-3 were −28 ± 40 mm with the Ocean retracker and 206 ± 30 mm with the Ice-1 retracker. The biases for Sentinel-3A were −14 ± 20 mm with the Samosa (Ocean like) retracker and 285 ± 20 mm with the OCOG (Ice-1-like) retracker. We have also evaluated the accuracy of these two altimeters over Lake Issykkul which reached to 3 cm, for both the instruments, using the Ocean retracker.

Augmentation Systems

2011 ◽  
pp. 283-293
Author(s):  
Mohammad S. Sharawi
Keyword(s):  
Performance Metrics ◽  
Satellite System ◽  
Space Vehicles ◽  
Gps Receivers ◽  
Commercial Use ◽  
Global Positioning ◽  
Almost All ◽  
Gps System ◽  
Year 2000 ◽  
Route Navigation

The global positioning satellite system (GPS) has been utilized for commercial use after the year 2000. Since then, GPS receivers have been integrated for accurate positing of ground as well as space vehicles. Almost all aircrafts nowadays rely on GPS based system for their take off, landing, and en-route navigation. Relying on GPS alone does note provide the meter level accuracy needed to guarantee safe operation of aircrafts. Thus several augmentation systems have been deployed worldwide to enhance the accuracy of the GPS system. Several augmentation systems that serve local as well as wide coverage areas are discussed in this chapter, specifically the LAAS system, the WAAS system as well as the EGNOS system. The architecture as well the performance metrics for each of these augmentation systems are presented and discussed.

Spatial Accuracy of UAV-Derived Orthoimagery and Topography: Comparing Photogrammetric Models Processed with Direct Geo-Referencing and Ground Control Points

GEOMATICA ◽  
2016 ◽  
Vol 70 (1) ◽  
pp. 21-30 ◽  
Author(s):  
Chris Hugenholtz ◽  
Owen Brown ◽  
Jordan Walker ◽  
Thomas Barchyn ◽  
Paul Nesbit ◽  
...  
Keyword(s):  
Satellite System ◽  
Base Station ◽  
Measurement Unit ◽  
Ground Control ◽  
Lower Grade ◽  
Control Points ◽  
Gps Receiver ◽  
Spatial Accuracy ◽  
Ground Control Points ◽  
Mean Square Errors

Mapping with unmanned aerial vehicles (UAVs) typically involves the deployment of ground control points (GCPs) to georeference the images and topographic model. An alternative approach is direct geo ref er encing, whereby the onboard Global Navigation Satellite System (GNSS) and inertial measurement unit are used without GCPs to locate and orient the data. This study compares the spatial accuracy of these approaches using two nearly identical UAVs. The onboard GNSS is the one difference between them, as one vehicle uses a survey-grade GNSS/RTK receiver (RTK UAV), while the other uses a lower-grade GPS receiver (non-RTK UAV). Field testing was performed at a gravel pit, with all ground measurements and aerial sur vey ing completed on the same day. Three sets of orthoimages and DSMs were produced for comparing spa tial accuracies: two sets were created by direct georeferencing images from the RTK UAV and non-RTK UAV and one set was created by using GCPs during the external orientation of the non-RTK UAV images. Spatial accuracy was determined from the horizontal (X,Y) and vertical (Z) residuals and root-mean-square-errors (RMSE) relative to 17 horizontal and 180 vertical check points measured with a GNSS/RTK base station and rover. For the two direct georeferencing datasets, the horizontal and vertical accuracy improved substantially with the survey-grade GNSS/RTK receiver onboard the RTK UAV, effectively reducing the RMSE values in X, Y and Z by 1 to 2 orders of magnitude compared to the lower grade GPS receiver onboard the non-RTK UAV. Importantly, the horizontal accuracy of the RTK UAV data processed via direct georeferencing was equivalent to the horizontal accuracy of the non-RTK UAV data processed with GCPs, but the vertical error of the DSM from the RTK UAV data was 2 to 3 times greater than the DSM from the non-RTK data with GCPs. Overall, results suggest that direct georeferencing with the RTK UAV can achieve horizontal accuracy comparable to that obtained with a network of GCPs, but for topographic meas urements requiring the highest achievable accuracy, researchers and practitioners should use GCPs.

The Research of Comprehensive Network Maintenance Management System Based on BDS & GPS

2014 ◽  
Vol 543-547 ◽  
pp. 2858-2861
Author(s):  
Xiao Mei Zhang ◽  
Yuan Cheng ◽  
Bing Qi ◽  
Chen Xiong
Keyword(s):  
Management System ◽  
Satellite System ◽  
Maintenance Management ◽  
System Structure ◽  
Network Systems ◽  
Basic Principles ◽  
Maintenance System ◽  
Network Maintenance ◽  
Security Of Network ◽  
Gps System

According to the existing network maintenance system and the basic principles of composition, this paper provides a terminal system scheme and network maintenance management system based on BeiDou Navigation Satellite System (BDS) compatible with GPS by analyzing the system structure, functional architecture and software architecture. Studies have shown that the BDS compatible with GPS system can manage and monitor personnel and vehicles in real time and improves the reliability and security of network systems.

scholarly journals Divagations on the Appropriate Satellite System from GNSS for Aviation

2021 ◽  
Vol 2021 (1) ◽  
pp. 75-92
Author(s):  
Andrzej Fellner ◽  
Robert Konieczka
Keyword(s):  
Satellite System ◽  
American Military ◽  
Satellite Signal ◽  
Gps System ◽  
Navigation Accuracy

Abstract American military satellite GPS system is an element of the global GNSS. It emits two codes: the precise and civil one. As late as in 2000, intentional interference that decreased precision of localization was introduced, allowing navigation accuracy of 20 m. GPS was made available to civil users, however, at their own responsibility. So, if we use GPS for our own goals, we must consider the errors that occur and their consequences. Nonetheless, commercial and operational needs determine the necessity of permanent access to satellite signal with appropriate consistency, accessibility, reliability and precision. Hence, natural and intentional errors are compensated for, using appropriate methods, based on a given activity.

scholarly journals Estimating and Analyzing Long-Term Multi-GNSS Inter-System Bias Based on Uncombined PPP

Sensors ◽  
2020 ◽  
Vol 20 (5) ◽  
pp. 1499
Author(s):  
Fan Zhang ◽  
Changjian Liu ◽  
Guorui Xiao ◽  
Xi Zhang ◽  
Xu Feng
Keyword(s):  
Full Rank ◽  
Gps Receiver ◽  
Galileo System ◽  
System Bias ◽  
The Mean ◽  
Good Signal ◽  
Gps System ◽  
Reference Clock

With the development of precise positioning with multi-GNSS, the inter-system bias (ISB) has become an issue that cannot be ignored. ISB is introduced from the differences among satellite reference clocks and different receiver hardware delay biases. To analyze the characteristics of multi-GNSS ISB, the precise point positioning (PPP) with full-rank uncombined model was derived for GLONASS, BDS, GALILEO, while the GPS receiver clock was selected as the reference. In addition, a recommended ISB parameter processing model was adopted. Data of 28-days from the Multi-GNSS Experiment (MGEX) station was used to estimate and analyze the ISB parameters. Based on a statistical analysis of the acquired data, results demonstrate that: (a) The rms of multi-GNSS PPP positional bias can reach 4.6 mm, 3.4 mm and 8.5 mm for E, N and U directions, respectively, which guarantees the reliability and accuracy of the ISB parameter solution. (b) The intra-day ISB time series of the three groups is relatively stable with standard deviations less than 0.6 ns. The ISB parameters between the GALILEO and GPS system are the most stable and the standard deviation was the smallest, at about 0.37 ns, which may be related to the good signal quality of the GALILEO system. (c) The mean of the single-day solution of the ISB parameter is not stable and the amplitude of the jump can be up to 60 ns. However, each station shows a similar variation for the same ISB parameter on the same day. The situation is independent of the type of receiver and antenna; however, it may be affected by the satellite reference clock of different systems. (d) There is a clear relationship between the ISB parameters and receiver types.

scholarly journals 57. Feasibility of the Global Positioning Satellite System for Rural Aeromedical Transport

1996 ◽  
Vol 11 (S2) ◽  
pp. S44-S44
Author(s):  
Russell F. Pruitt ◽  
Ronald F. Sing ◽  
C. W. Austin ◽  
W. Joseph Messick
Keyword(s):  
Rural Areas ◽  
Current System ◽  
Prospective Trial ◽  
Satellite System ◽  
Ease Of Use ◽  
Gps Receivers ◽  
Global Positioning ◽  
Level I ◽  
Aeromedical Transport ◽  
Gps System

Aeromedical navigation to the scene of an accident using navigational assistance computer mapping software (NACM) can be difficult in rural areas due to the lack of topographic landmarks. In these instances, navigation is made easier using the Global Positioning Satellite (GPS) system to determine latitude and longitude.Purpose: To determine the reliability and feasibility of portable GPS receivers compared with our current system of NACM (MAP EXPERT®) in the navigation of aeromedical transport flights.Design: A non-randomized prospective trial comparing flights using either GPS or NACM. Setting: Flight program at a Level I trauma center.Methods: GPS receivers (for transmitting location) were carried by half the helicopters and ground EMS units. The NACM system was used to transmit the location of the accident to the other flights. Data on flight time, distance, and accident location were collected. Pilots and EMS personnel using the portable GPS system completed a questionnaire regarding accuracy, reliability, and ease of use.Results: This study included 51 flights; GPS (n = 26) and NACM (n = 25). There was no difference in the miles flown per minute in the NACM group (1.69 miles/minute) compared with the GPS group (1.70 miles/minute). Pilots and EMS personnel rated the GPS reliable, accurate, and easy to use for navigation.

Design and Implementation of Dual-Channel and Dual-Mode Timing Module Based on Beidou & GPS

2012 ◽  
Vol 241-244 ◽  
pp. 2402-2406
Author(s):  
Xiao Shan Pan ◽  
Zi Guan Zhou ◽  
Min Zhou ◽  
Bing Qi
Keyword(s):  
Satellite System ◽  
Navigation Satellite ◽  
Dual Mode ◽  
Service Demand ◽  
Gps Navigation ◽  
Beidou Navigation Satellite System ◽  
Dual Channel ◽  
The Status ◽  
Baseband Processor ◽  
Gps System

Against the Status quo that satellite timing service in many fields of China mainly relies on the GPS system, for full use of the Beidou navigation satellite system with our own intellectual property, this paper presented a chip-level solution of dual-channel and dual-mode timing modules based on the Beidou-2 and GPS navigation system. The timing principle of Beidou navigation satellite system was first introduced, and then the hardware design of the timing module was presented with selection of highly-integrated RF chip and baseband processor chip. Furthermore, many kinds of output interfaces were designed to meet diverse service demand. By analyzing the format of the received signal, the flow chart for extracting timing information was also given. Finally, the designed timing module was tested by using the developed timing display system and test results show that the module has a better timing performance.

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