The NavIC is an Indian satellite based navigation system uses the L5 and S-band signals to provide 10 m (metres) and 0.1 m positioning accuracy services for civilian and military users respectively. ...The positioning accuracy of the NavIC system is affected by many sources of error, and the ionospheric delay (Ionodelay) error is the dominant error in all. We observed the NavIC L5 band Iono delay and positioning accuracy under the influence of the intense geomagnetic storm (D
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= −124, KP = 8) that occurred on 8 September 2017 at various geographical locations. Here, the NavIC S band is explored to observe the impact of geomagnetic storm (8 September 2017) and the performance is compare with NavIC L5 band at the low-latitude SVNIT Surat station (21.16° N, 72.78° E) for the second week of September 2016, 2017 and 2018. To observe the impacts of seasonal variation on the NavIC L5 and S band Ionodelay is also measured for the days of June 2016 to May 2017. It has been observed that in the days of the Summer season and an intense geomagnetic stormy day (8 September 2017) NavIC performance has faced challenges for positioning accuracy. It has been also observed the compare to NavIC L5 band S band faced more challenges for positioning accuracy. After correcting the ionosphere, troposphere, clock, and other deviations, the average ∼70% NavIC positioning accuracy is improved for the overall observed duration, conditions, and locations.
This study describes the current state of the art related to the assessment of the positional accuracy of spatial databases based on lines. The use of this type of element of spatial databases has ...increased in recent years because of the current possibilities of acquisition and sharing data of routes, roads, etc. Nowadays, users are also contributors and this supposes that the spatial quality of data acquired and shared by non-experts must be assessed as is the case with data produced by institutions and enterprises. In this context, several methods based on lines have been developed up to this time for several purposes. This study reviews these methods, analyzing their characteristics, measures, etc. In addition, more than 30 applications of these methods are also summarized. These applications include control of generalized and digitized lines, control of spatial databases, analysis of the displacement of lines between dates, etc
Three validation techniques for performing positional accuracy assessments in georeferencing were critically reviewed in this study, with an aim of estimating the possibilities of identifying and ...removing the geometric deformations of raster images. A validation technique based on the residuals of tie points, Hold-Out and the Cross-Validation technique was implemented within PlanTra software. Accuracy indicators, obtained through these techniques, using different functional transformation models, were thoroughly tested on a typical area. It has been proven that the Cross-Validation technique produces a much more reliable estimation of accuracy in comparison to the standard approach based on the residuals of tie points.
This study evaluates the applicability of different models of coordinate transformation between local and global geodetic datums. The results indicate the grid-based method as the best solution, ...assuming a sufficient density of tie points. Transformation based on a limited number of tie points, which do not reflect the real state of the survey basis in a particular area, have limited possibilities to reduce nonuniform and unequally distributed distortions that are usually found in the spatial data. This inevitably leads to the degradation of accuracy of transformation results, which is unacceptable. By using the optimal resolution grid model, which includes geodetic points from the area of the cadastral municipality that is being transformed, much better results are achieved compared to the model of distortion shifts used in the Federation of Bosnia and Herzegovina.
The positional accuracy of Navigation with the Indian Constellation (NavIC)/Indian Regional Navigation Satellite System (IRNSS) in the low latitudes of the Indian region during the intense ...geomagnetic storm of 8 September 2017 being reported first time. The existence of an intense geomagnetic storm is verified with several geomagnetic indices and interplanetary field parameters. The Total Electron Content (TEC) maps from the International GNSS Service (IGS) data and the thermosphere O/N2 ratio maps from the Global Ultra Violet Imager (GUVI) are also used in the study. The one week of data (3-9 September 2017) are collected based on equatorial region (Trivandrum) and Equatorial Ionization Anomaly (EIA) region (e.g. Surat, Bombay, Hyderabad and Gandhinagar), from India, using the Accord NavIC/IRNSS dual-frequency (L5 and S-band) receivers. For the intense storm day, a comparative study is being carried out for TEC, ionospheric delay and positional accuracy for L5 band. The observations perceive the positive impact in the equatorial region while the negative impact for EIA region, with reference to quiet days of the observed week. The average ∼70% and further ∼25% NavIC/IRNSS system positional accuracy is improved by applying ionospheric correction and augmenting NavIC/IRNSS with GPS system respectively. This study is very much important in satellite-based navigation application for Precise Point Positioning (PPP).
The Northeast black soil region is China’s vital commercial grain base. However, severe soil erosion on slope farmland poses a significant threat to this region’s sustainable agricultural ...productivity. The transition from traditional downslope ridging to contour ridging (briefly referred to as “contour ridging”) is one of the primary sustainable measures for preventing soil erosion on slope farmland. By integrating high-precision Digital Elevation Models (DEMs) and design standards, ArcMap can plan the orientation and position of contour ridgelines and estimate the reduction in soil erosion on slope farmland after implementing contour ridging. Therefore, the degree of discrepancy between the designed and implemented positions of the contour ridgelines directly affects the effectiveness of contour ridging and the precision in evaluating its impacts and benefits. This study aims to assess the position accuracy of contour ridgelines designed by ArcMap 10.5 (here after ArcMap) using high-precision DEMs obtained from unmanned aerial vehicles (UAV). For this purpose, three fields where contour ridging had already been implemented were selected in the Sanjiang Plain of Heilongjiang Province, China. CORS RTK was used to measure the XYZ coordinates of verification points along implemented ridges precisely. Those measured coordinates were compared with the designed ridgeline positions to analyze the positional discrepancies between the designed and implemented ridgelines. The results indicated the following: (1) The average slope gradient along contour ridgelines measured in the field (0.5~0.6°) was relatively close to that along the ridgelines designed using ArcMap (0.6°), and the elevation changes along most of the contour ridgelines showed a pattern of being higher in the middle and lower on both sides. (2) The positional offset between most of the measured and designed ridgelines was less than the width of a single ridge (1.3 m), and the median offset was one-third of the width of a single ridge. (3) The positional offset caused by the movement of ridging machinery could be larger than the offset resulting from the baseline setup, and verification points with larger positional offsets were often located at the edges of the plots as well as turns of the ridgelines. Therefore, during the designing ridgelines process, the turns should be made as smooth as possible. During ridging, reducing the speed at these turns to minimize errors and maintain the accuracy of the ridgeline was recommended. The findings of this study can provide a scientific basis to improve contour ridging design and effect prediction in slope farmland to control soil erosion and enhance agricultural sustainability.
The research consisted of simulating the movement of a single vehicle in relation to the swarm leader on a square-shaped path, taking into account measurement errors characteristic of typical cheap ...navigation devices and the hydroacoustic system. The research showed that these methods allow for estimating position coordinates with an accuracy of about 0.5 m (RMS) in the case of a calibrated navigation system and about 3.6 m (RMS) in the case of a non-calibrated navigation system. It also showed that it can provide a higher accuracy of estimating position coordinates in terms of abeam angles of the swarm leader (relative bearing equal to approximately ±90°), as well as while ensuring minimizing systematic errors values and proper estimation of mean errors values concerning course and speed measurements.
La demanda de documentos cartográficos por parte de la sociedad que creció en todo el mundo, incluido Brasil. El avance de las geotecnologías asociadas a la publicación de datos de forma gratuita ...permite que cada vez sea más accesible esta adquisición, ya que actualmente, es posible utilizar imágenes, incluso de alta resolución de esta forma; por ejemplo, las imágenes de la plataforma Google Earth. El objetivo del presente estudio es evaluar la exactitud posicional de estas imágenes. Las áreas de estudio fueron seleccionadas mediante el proceso de muestreo aleatorio, haciendo la selección de un estado por región. Los estados seleccionados fueron Alagoas (noreste), Río de Janeiro (sureste), Santa Catarina (sur), Goiás (centro-oeste) y Tocantins (norte). Fueron utilizados puntos de control medidos en el campo con el uso de GNSS para evaluar la exactitud posicional. Los resultados obtenidos en el presente estudio indican que la imagen proporcionada por la plataforma Google Earth tiene una exactitud posicional compatible con la escala de 1:25 000 clase B del EPC —Estándar de Precisión Cartográfica de Brasil, lo que indica su uso solo para mapeos en la escala de 1:25 000.
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