RELIABILITY OF THE GPS CARRIER-PHASE FIX SOLUTION UNDER HARSH CONDITION

Once the unknown integer ambiguity values are resolved, the GPS carrier phase observation will be transformed into a millimeter-level precision measurement. However, GPS observation are prone to a variety of errors, making it a biased measurement. There are two components in identifying integer ambiguities: estimation and validation. The estimation procedure aims to determine the ambiguity's integer values, and the validation step checks whether the estimated integer value is acceptable. Even though the theory and procedures for ambiguity estimates are well known, the topic of ambiguity validation is still being researched. The dependability of computed coordinates will be reduced if a false fixed solution emerges from an incorrectly estimated ambiguity integer value. In this study, the reliability of the fixed solution obtained by using several base stations in GPS positioning was investigated, and the coordinates received from these bases were compared. In a conclusion, quality control measures such as employing several base stations will improve the carrier phase measurement's accuracy.

Map matching for circular road via contextual voting

Due to the limitation of positioning devices, there is a certain error between GPS positioning data and the real location on the map, and the positioning data needs to be processed to have better usability. For example, accurate location is needed for traffic flow control, automatic driving navigation, logistics tracking, etc. There are few studies specifically for circular road sections. In addition, many existing map matching methods based on Hidden Markov model (HMM) also have the problem that GPS points are easily to be matched to tangent or non-adjacent road sections at circular road sections. Therefore, the contextual voting map matching method for circular road sections (STDV-matching) is proposed. The method proposes multiple subsequent point direction analysis methods based on STD-matching to determine entry into the circular section, and adds candidate section frequency voting analysis to reduce matching errors. The effectiveness of the proposed method is verified at the circular section by comparing it with three existing HMM methods through experiments using two real map and trajectory datasets.

Eyjafjallajökull Volcanic Ash 2010 Effects on GPS Positioning Performance in the Adriatic Sea Region

The Eyjafjallajökull volcanic ash crisis in 2010 temporarily suspended European air traffic operations, as the 39-day eruption caused widely dispersed ashes to enter the lower atmosphere. In this paper, we assessed the effects of this event on the ionosphere layer and, consequently, on GPS positioning. We collected and analysed the data from four IGS stations, nearest to the volcano, for the month of April 2010. We recorded Vertical Total Electron Content (VTEC) time series, analysed their dynamics, and compared them with the GPS positioning errors of a commercial-grade, un-aided, single-frequency GPS receiver (simulating the response of a mass-market GPS receiver). The geomagnetic indices during the time period show little geomagnetic disturbance, especially during the volcanic event. Our results show an enhancement in ionosphere error by up to 15% during the volcanic ash event and an enhanced variance in GPS position components errors. This study reveals the potential impact of the charged volcanic ash on single-frequency, unaided GPS positioning accuracy in the Adriatic Sea region and establishes a foundation for studying similar events in future.

Investigation of GPS Positioning Accuracy Near a Deciduous Forest Area

This article evaluates the accuracy and performance of GPS positioning near a forest area. In such cases, positions are calculated from weak signals that tend to be less accurate. Moreover, the results show that there were significant differences depending on season (May vs. October) regarding the accuracy and precision of the measured coordinates; also, accuracies were different depending on the seasonal forest characteristics. Therefore, practical recommendations for each case were established in order to help foresters select the most suitable situation. The results indicated that the season was a significant factor for the GPS surveys.

GEOSPATIAL APPROACH FOR GEOLOGICAL INVESTIGATION AT DISTRICT OF MERSING

Effective geological information evaluation is essential for accurate site characterization. A major concern in geological mapping is to locate the accurate location of the geological information. The geoinformation approach such as precise GPS surveying and UAV mapping could be integrated with other geospatial information to augment the geological information. This research aims to integrate the geoinformation approach into geological structure mapping. To achieve the overall purpose of the study, the objective identified was the establishment of a high-precision control point by using Precise GPS measurement in the study area. Therefore, the establishment of GPS data observations involves the establishment of primary networks and several GPS controls points within the study area. Subsequently, the GPS positioning has been processed to produce a topographic information map and to support the collection of geological data in the study area. It is hoped that the integration of the geoinformation approach has been provided a significant increase in geological information at the district of Mersing.

Performance of GPS Positioning in the Presence of Irregularities in the Auroral and Polar Ionospheres during EISCAT UHF/ESR Measurements

Irregularities in the spatial distribution of ionospheric electron density introduce temporal fluctuations in the intensity and phase of radio signals received from Global Navigation Satellite Systems (GNSS). The impact of phase fluctuations originating from irregularities in the auroral and polar ionospheres on GPS positioning was investigated on three days in March 2018 in the presence of quiet-to-moderately disturbed magnetic conditions by combining measurements from GPS and EISCAT UHF/ESR incoherent scatter radars. Two different positioning solutions were analysed: broadcast kinematic (BK) and precise static (PS). The results show that the propagation through irregularities induced residual errors on the observables leading to an increase in the positioning error, in its variability, and in the occurrence of gaps. An important aspect emerging from this study is that the variability of the 3-D positioning error was reduced, and the presence of gaps disappeared when the positioning solutions were evaluated at a 1 s rate rather than at a 30 s rate. This is due to the transient nature of residual errors that are more significant over 30 s time intervals in the presence of irregularities with scale size between few kilometres in the E region to few tens of kilometres in the F region.

Realization of GPS Dynamic Hijacking Based on Software Radio

GPS positioning technology has a wide range of use scenarios, but due to the known characteristics of GPS signal open reception and modulation methods, many solutions can easily deceive GPS signals. Once this technology is abused in violation of regulations, it may cause major safety and property losses. In order to better study the anti-hijacking technology of PGS signals, this article starts with the generative dynamic hijacking of PGS, gives the implementation method based on software radio, and further learns the code phase and dopper between asynchronous hijacking and synchronous hijacking through software radio. The compensation calculation method of Leer frequency shift parameters, and verified the effect of the software radio’s GPS dynamic hijacking implementation method through examples, and provide theoretical support for the design and improvement of future anti-hijacking systems.

EFFECT OF USING DIFFERENT SATELLITE EPHEMERIDES ON GPS PPP AND POST PROCESSING TECHNIQUES

The orbital error is one of the errors in GPS which affect the accuracy of GPS positioning. In this research GPS broadcast, ultra-rapid, rapid and precise satellite ephemerides are used for processing different baseline lengths among some CORS stations by using the Trimble Business Center software (TBC) and different satellite ephemerides (NRCan ultra-rapid, NRCan rapid and IGS final) are tested in CSRS-PPP online application at the same CORS stations. In this research, when using TBC software for processing the different baseline lengths by using the different satellite ephemerides and compared the coordinates of CORS stations which obtained from the different satellite ephemerides with each other. The results showed that the best satellite ephemerides closest to rapid and final satellite ephemerides are the ultra-rapid (00 UTC) and ultra-rapid (06 UTC). When processing the same CORS stations which used at TBC on CSRSPPP online application by using the different satellite ephemerides it is found also that the NRCan ultra-rapid closest to final satellite ephemerides.