ASSESSING THE QUALITY OF THE NEAR REAL-TIME REGIONAL VTEC MAPS PRODUCED BY LA PLATA UNIVERSITY IN ABSOLUTE GNSS POSITIONING OVER BRAZIL

Pereira, Thiago Amaral; Machado, Wagner Carrupt; Marques, Haroldo Antonio

doi:10.1590/s1982-21702021000400028

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ORIGINAL ARTICLE • Bol. Ciênc. Geod. 27 (04) • 2021 • https://doi.org/10.1590/s1982-21702021000400028 copy

ASSESSING THE QUALITY OF THE NEAR REAL-TIME REGIONAL VTEC MAPS PRODUCED BY LA PLATA UNIVERSITY IN ABSOLUTE GNSS POSITIONING OVER BRAZIL

Avaliação da qualidade dos mapas de VTEC regionais em quase tempo real produzidos pela Universidade de La Plata no posicionamento GNSS absoluto no Brasil

Authorship SCIMAGO INSTITUTIONS RANKINGS

Abstract:

At the end of 2018, the Laboratorio de Meteorología Espacial, Atmósfera Terrestre, Geodesia, Geodinámica, Diseño de Instrumental y Astrometría, from La Plata University, started providing near real-time Regional Ionosphere Maps (MAGN) with high spatial and temporal resolutions and low latency. In this paper, we show a performance evaluation of these new ionosphere maps in space of positioning during the first year (2019) of available data. The assessment was carried out through absolute GNSS positioning using the in-house RT-PPP software. Data from five stations in Brazil, distributed in different geomagnetic latitudes, were processed. The performance of the MAGN was evaluated comparing the coordinates estimated using MAGN maps and the Global Ionosphere Maps (GIM) from CODE, both concerning the PPP ionosphere-free combination solution. Although it has been found that, in general, the MAGN and CODE solutions are compatible, the former provided better positioning result (8.5%) in the altimetric (up) component. However, when an atypical behavior in the MAGN solution at the end of the year 2019 as well as days of incomplete maps were removed from the analysis, the solution with MAGN becomes slightly better than CODE, providing an improvement of 8.6% in the up component.

Keywords:
GNSS positioning; Regional Ionosphere Maps; Global Ionosphere Maps; MAGGIA

Feature	CODE’S GIM	MAGN
Spatial resolution	2.5° x 5° (Lat and Long)	0.5° x 0.5° (Lat and Long)
Temporal Resolution	1 h	15 min
Latency	14 Days	few minutes
GNSS Network	IGS	SIRGAS-CON+
GNSS System	GPS	GPS+GLONASS+Galileo+BDS
DCB	Available	Not Available

Effect	Strategy
Ionosphere - 1st order	Ion-free
	Stochastic process
	Ionosphere maps
Troposphere	Hopfield + GPT
	GMF + ZTD from CPTEC
	VMF1 + ZTD from ECMWF
	ZHD constrained + ZWD estimated (Random Walk)
PVC (receiver and satellite)	Absolute antenna Phase Center Corrections (PCO e PCV)
Precise Ephemeris	From IGS
Satellite clock error	Estimated
Differential Code Bias	Monthly solutions from CODE
Ambiguities	Float solution

SCCA		DE (m)		DN (m)		DU (m)
SCCA		CODE	MAGN	CODE	MAGN	CODE	MAGN
Mean	I	-0.025	-0.800	0.062	-0.076	-0.267	-0.399
	II	-0.028	-0.071	0.061	-0.070	-0.273	-0.278
	III	-0.027	-0.068	0.063	-0.069	-0.270	-0.270
Maximum Absolute	I	0.293	0.333	0.256	0.303	1.221	1,625
	II	0.237	0.333	0.256	0. 303	1.221	1.341
	III	0.237	0.316	0.256	0. 303	1.221	1.053
Std. Dev.	I	0.078	0.093	0.070	0.073	0.323	0.365
	II	0.069	0.096	0.073	0.075	0.338	0.285
	III	0.070	0.097	0.072	0.073	0.335	0.270
RMSE	I	0.082	0.123	0.093	0.106	0.419	0.542
	II	0.075	0.120	0.095	0.103	0.435	0.398
	III	0.075	0.118	0.096	0.101	0.430	0.382

SJSP		DE (m)		DN (m)		DU (m)
SJSP		CODE	MAGN	CODE	MAGN	CODE	MAGN
Mean	I	-0.085	-0.125	0.146	0.057	-0.907	-0.979
	II	-0.080	-0.103	0.155	0.057	-0.851	-0.834
	III	-0.078	-0.100	0.155	0.057	-0.855	-0.833
Maximum Absolute	I	0.293	0.466	0.325	0.384	1.844	2.254
	II	0.281	0.466	0.325	0.308	1.645	1.665
	III	0.281	0.466	0.325	0.308	1.645	1.665
Std. Dev.	I	0.089	0.128	0.064	0.075	0.328	0.405
	II	0.087	0.128	0.064	0.075	0.302	0.288
	III	0.088	0.129	0.065	0.075	0.304	0.279
RMSE	I	0.123	0.179	0.159	0.094	0.966	1.060
	II	0.119	0.164	0.168	0.094	0.905	0.884
	III	0.118	0.163	0.168	0.094	0.908	0.878

MTIT		DE (m)		DN (m)		DU (m)
MTIT		CODE	MAGN	CODE	MAGN	CODE	MAGN
Mean	I	0.056	0.037	-0.061	-0.066	-0.590	-0.739
	II	0.050	0.008	-0.052	-0.048	-0.617	-0.655
	III	0.051	0.012	-0.051	-0.049	-0.612	-0.635
Maximum Absolute	I	0.500	0.573	0.317	0.382	1.652	2.087
	II	0.397	0.499	0.286	0.382	1.652	1.787
	III	0.397	0.388	0.286	0.277	1.652	1.337
Std. Dev.	I	0.128	0.134	0.086	0.115	0.323	0.355
	II	0.116	0.113	0.078	0.102	0.336	0.299
	III	0.114	0.108	0.078	0.096	0.330	0.270
RMSE	I	0.140	0.139	0.105	0.133	0.673	0.821
	II	0.126	0.113	0.094	0.112	0.703	0.721
	III	0.125	0.108	0.093	0.108	0.696	0.691

PIFL		DE (m)		DN (m)		DU (m)
PIFL		CODE	MAGN	CODE	MAGN	CODE	MAGN
Mean	I	0.027	0.007	0.141	0.041	-1.033	-1.007
	II	0.002	-0.022	0.143	0.038	-0.995	-0.799
	III	0.001	-0.024	0.146	0.039	-0.997	-0.794
Maximum Absolute	I	0.461	0.512	0.482	0.275	1.805	3.045
	II	0.351	0.495	0.482	0.245	1.761	2.073
	III	0.351	0.495	0.482	0.245	1.761	1.986
Std. Dev.	I	0.119	0.162	0.087	0.083	0.276	0.519
	II	0.101	0.146	0.090	0.080	0.278	0.307
	III	0.100	0.148	0.089	0.078	0.275	0.295
RMSE	I	0.122	0.162	0.166	0.093	1.070	1.134
	II	0.102	0.148	0.169	0.089	1.035	0.858
	III	0.100	0.149	0.171	0.087	1.036	0.847

AMCR		DE (m)		DN (m)		DU (m)
AMCR		CODE	MAGN	CODE	MAGN	CODE	MAGN
Mean	I	-0.064	0.013	0.438	0.288	-1.119	-1.111
	II	-0.060	-0.022	0.475	0.320	-1.089	-1.019
	III	-0.058	-0.020	0.473	0.324	-1.089	-0.994
Maximum Absolute	I	0.355	0.481	0.781	0.618	1.812	2.714
	II	0.306	0.393	0.781	0.592	1.786	2.714
	III	0.306	0.354	0.781	0.592	1.786	2.619
Std. Dev.	I	0.106	0.131	0.155	0.152	0.284	0.381
	II	0.096	0.109	0.144	0.144	0.289	0.356
	III	0.096	0.107	0.144	0.141	0.287	0.313
RMSE	I	0.124	0.132	0.465	0.326	1.156	1.176
	II	0.113	0.101	0.497	0.351	1.129	1.081
	III	0.112	0.108	0.495	0.354	1.127	1.042

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[1] All three authors were responsible for the methodology, the analyzes, and the manuscript writing. Individually, Thiago Amaral Pereira was responsible for data acquisition and processing as well as for initial analysis; Wagner Carrupt Machado was the research proponent and has done deeper results analysis, and Haroldo Antonio Marques has also done deeper analysis and provided the GNSS data processing software.