A method of improving ambiguity fixing rate for post-processing kinematic GNSS data

Abstract Smartphones with their capability to receive Global Navigation Satellite Systems (GNSS) signals can be currently considered the most common devices used for positioning tasks, including forestry applications. This study focuses on possible improvements related to two crucial changes implemented into Android smartphone positioning in the last 3 years – dual-frequency (L1/L5) GNSS receivers and the possibility of recording raw GNSS data. The study comprises three experiments: (1) real-time measurements of individual points, (2) real-time recording of trajectories, and (3) post-processing of raw GNSS data provided by the smartphone receiver. The real-time tests were conducted using final positions provided by the internal receiver, i.e. without further processing or averaging. The test on individual points has proven that the Xiaomi Mi8 smartphone with a multi-constellation, dual-frequency receiver was the only device whose accuracy was not significantly different from single-frequency mapping-grade receiver under any conditions. The horizontal accuracy of most devices was lower during leaf-on season (root mean square errors between 5.41 and 12.55 m) than during leaf-off season (4.10–11.44 m), and the accuracy was significantly better under open-area conditions (1.72–4.51 m) for all tested devices when compared with forest conditions. Results of the second experiment with track recording suggest that smartphone receivers are better suited for dynamic applications – the mean shift between reference and measured trajectories varied from 1.23 to 5.98 m under leaf-on conditions. Post-processing of the raw GNSS data in the third experiment brought very variable results. We achieved centimetre-level accuracy under open-area conditions; however, in forest, the accuracies varied from meters to tens of meters. Observed loss of the signal strength in the forest represented ~20 per cent of the open-area value. Overall, the multi-constellation, dual-frequency receiver provided more robust and accurate positional solutions compared with single-frequency smartphones. Applicability of the raw GNSS data must be further studied especially in forests, as the provided data are highly susceptible to multipath and other GNSS adverse effects.

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Post-processing of GNSS data using open source software for structural deformation monitoring

2017 Fifth International Conference on Aerospace Science & Engineering (ICASE) ◽

10.1109/icase.2017.8374270 ◽

2017 ◽

Author(s):

Saad Babar Abbasi

Keyword(s):

Open Source ◽

Open Source Software ◽

Deformation Monitoring ◽

Structural Deformation ◽

Post Processing ◽

Gnss Data

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Assessment of Static Positioning Accuracy Using Low-Cost Smartphone GPS Devices for Geodetic Survey Points’ Determination and Monitoring

Applied Sciences ◽

10.3390/app10155308 ◽

2020 ◽

Vol 10 (15) ◽

pp. 5308 ◽

Cited By ~ 4

Author(s):

Marcin Uradziński ◽

Mieczysław Bakuła

Keyword(s):

Mobile Phones ◽

Carrier Phase ◽

Low Cost ◽

Satellite System ◽

Base Station ◽

Dual Frequency ◽

Post Processing ◽

Positioning Accuracy ◽

Static Mode ◽

Ambiguity Fixing

Recent developments enable to access raw Global Navigation Satellite System (GNSS) measurements of mobile phones. Initially, researchers using signals gathered by mobile phones for high accuracy surveying were not successful in ambiguity fixing. Nowadays, GNSS chips, which are built in the latest smartphones, deliver code and primarily carrier phase observations available for detailed analysis in post-processing applications. Therefore, we decided to check the performance of carrier phase ambiguity fixing and positioning accuracy results of the latest Huawei P30 pro smartphone equipped with a dual-frequency GNSS receiver. We collected 3 h of raw static data in separate sessions at a known point location. For two sessions, the mobile phone was mounted vertically and for the third one—horizontally. At the same time, a high-class geodetic receiver was used for L1 and L5 signal comparison purposes. The carrier phase measurements were processed using commercial post-processing software with reference to the closest base station observations located 4 km away. Additionally, 1 h sessions were divided into 10, 15, 20 and 30 min separate sub-sessions to check the accuracy of the surveying results in fast static mode. According to the post-processing results, we were able to fix all L1 ambiguities based on Global Positioning System (GPS)-only satellite constellation. In comparison to the fixed reference point position, all three 1 h static session results were at centimeters level of accuracy (1–4 cm). For fast static surveying mode, the best results were obtained for 20 and 30 min sessions, where average accuracy was also at centimeters level.

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EVALUATION OF THE POSITIONAL QUALITY THROUGH THE POST-PROCESSING OF RAW GNSS DATA FROM A SMARTPHONE VIA DIFFERENT SATELLITE POSITIONING METHODS

Boletim de Ciências Geodésicas ◽

10.1590/s1982-21702020000400020 ◽

2020 ◽

Vol 26 (4) ◽

Author(s):

Allan Gomes ◽

Claudia Pereira Krueger

Keyword(s):

Dual Frequency ◽

Post Processing ◽

Raw Data ◽

Static Mode ◽

Geodetic Coordinates ◽

Satellite Positioning ◽

The One ◽

Gnss Data ◽

First Time

Abstract: Since the introduction of the Android 7 in August 2016, it has become possible to use raw data collected by GNSS sensors present in some Android smartphones and tablets. Therefore, it became possible, for the first time, to perform the post-processing of the data, which means to obtain coordinates that are more accurate than usual, from meters to decimeters. In addition, among the technological innovations in the context of positioning via smartphones, it is mentioned the use of modern GNSS sensors, like the one used by Xiaomi Mi 8, which was the first smartphone to integrate a dual-frequency GNSS sensor. In this research, data collection campaigns were carried out in static mode to evaluate the quality of geodetic coordinates obtained from Mi 8. Using freely available applications that store raw data in files in RINEX format, the data was post-processed with different positioning methods and with different software, including the freely available IBGE-PPP online service in Brazil. The results of this research show that it is possible to obtain geodetic coordinates with an accuracy at decimeter order, which indicates that the methodology can be used in some engineering applications.

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APPLYING THE ISF TECHNOLOGY TO PRODUCE THE CAR PART MODELS

Science and Technology Development Journal ◽

10.32508/stdj.v13i4.2181 ◽

2010 ◽

Vol 13 (4) ◽

pp. 91-98

Author(s):

Tuan Dinh Phan ◽

Binh Thien Nguyen ◽

Dien Khanh Le ◽

Phuong Hoang Pham

Keyword(s):

Rapid Prototyping ◽

Incremental Sheet Forming ◽

Cad Model ◽

Post Processing ◽

Technological Parameters ◽

Batch Production ◽

Complex Products ◽

3D Cad ◽

Real Size ◽

Single Batch

The paper presents an application the research results previously done by group on the influence of technological parameters to the deformation angle and finish surface quality in order to choose technology parameters for the incremental sheet forming (ISF) process to produce products for the purpose of rapid prototyping or single-batch production, including all steps from design and process 3D CAD model, calculate and select the technological parameters, setting up manufacturing and the stage of post-processing. The samples formed successfully showed high applicability of this technology to practical work, the complex products with the real size can be produced in industries: automotive, motorcycle, civil...

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