scholarly journals Towards a Topographically-Accurate Reflection Point Prediction Algorithm for Operational Spaceborne GNSS Reflectometry—Development and Verification

2021 ◽  
Vol 13 (5) ◽  
pp. 1031
Author(s):  
Lucinda King ◽  
Martin Unwin ◽  
Jonathan Rawlinson ◽  
Raffaella Guida ◽  
Craig Underwood
Keyword(s):  
Global Climate ◽  
Prediction Algorithm ◽  
Navigation Systems ◽  
Reflection Point ◽  
Digital Elevation ◽  
Data Gaps ◽  
Gnss Reflectometry ◽  
Elevation Model ◽  
Satellite Navigation Systems ◽  
Ocean Wind

GNSS Reflectometry (GNSS-R), a method of remote sensing using the reflections from satellite navigation systems, was initially envisaged for ocean wind speed sensing. In recent times there has been significant interest in the use of GNSS-R for sensing land parameters such as soil moisture, which has been identified as an Essential Climate Variable (ECV). Monitoring objectives for ECVs set by the Global Climate Observing System (GCOS) organisation include a reduction in data gaps from spaceborne sources. GNSS-R can be implemented on small, relatively cheap platforms and can enable the launch of constellations, thus reducing such data gaps in these important datasets. However in order to realise operational land sensing with GNSS-R, adaptations are required to existing instrumentation. Spaceborne GNSS-R requires the reflection points to be predicted in advance, and for land sensing this means the effect of topography must be considered. This paper presents an algorithm for on-board prediction of reflection points over the land, allowing generation of DDMs on-board as well as compression and calibration. The algorithm is tested using real satellite data from TechDemoSat-1 in a software receiver with on-board constraints being considered. Three different resolutions of Digital Elevation Model are compared. The algorithm is shown to perform better against the operational requirements of sensing land parameters than existing methods and is ready to proceed to flight testing.

New methodical approaches to mapping of geosystems (by the example of Baikalian Siberia’s geosystems)

2018 ◽  
Vol 937 (7) ◽  
pp. 23-34 ◽  
Author(s):  
I.N. Vladimirov
Keyword(s):  
Global Climate ◽  
Remote Sensing Data ◽  
Field Research ◽  
Scientific Basis ◽  
Nature Management ◽  
Climate Data ◽  
Structural Dynamic ◽  
Digital Elevation ◽  
North Asia ◽  
Elevation Model

The article considers a new approach to landscape mapping based on the synthesis of remote sensing data of high and medium spatial resolution, a digital elevation model, maps of various thematic contents, a set of global climate data, and materials of field research. The map of the Baikalian’s Siberia geosystems is based on the principles of the multistage regional-typological and structural-dynamic classification of geosystems proposed by Academician V.B. Sochava. The structure of the geosystems of the Baikalian Siberia is characterized by great complexity, both in the set of natural complexes and in the degree of their contrast. The regional classification range covers the geosystems inherent in different subcontinents of Asia and reflects their interpenetration, being a unique landscape-situational example of Siberian nature within North Asia. The map of the geosystems of the Baikalian Siberia reflects the main structural and dynamic diversity of geosystems in the region in the systems of their geographic and genetic spatial structures. These landscape cartographic studies fit into a single system of geographic forecasting and create a new fundamental scientific basis for developing recommendations for optimizing nature management in the Baikal region within the framework of implementing state environmental policy.

Airborne GNSS reflectometry for coastal monitoring of sea state

2020 ◽  
Author(s):  
Mario Moreno ◽  
Maximilian Semmling ◽  
Georges Stienne ◽  
Serge Reboul ◽  
Jens Wickert
Keyword(s):  
Carrier Phase ◽  
Signal Amplitude ◽  
Navigation Systems ◽  
Sea State ◽  
Wind Retrieval ◽  
The North ◽  
Front End ◽  
The North Sea ◽  
Gnss Reflectometry ◽  
Satellite Navigation Systems

<p>Global Satellite Navigation Systems (GNSS) applications like navigation and positioning generally focus on the use of the direct radio signal broadcasted by the navigation satellites. From these signals, very highly precise coordinates can be obtained. However, there is a proportion of signals, that do not reach the receivers directly, that is, the signals that are reflected off Earth’s surface before reaching the receivers. That phenomenon gave way to one of the techniques that is taking an important role in the scope of GNSS remote sensing called GNSS-Reflectometry (GNSS-R). Due to the high reflection coefficient of the water and its importance within the climate system, the ocean is one of the surfaces with greatest interest in GNSS-R research projects. The objective of this study is to retrieve information about ocean height measured through the delay of the signal, and sea state and wind retrieval (ocean surface roughness) from the analysis of the signal amplitude.</p><p>During this study, GNSS-R measurements were executed along the North Sea coast between the cities of Calais and Boulogne, France, onboard of a gyrocopter. The setup consisted of a front-end data recorder with a right-handed circular polarization (RHCP) antenna. The campaign was conducted in July 2019 within a total of 9h 40m flight time. Each flight was performed at an altitude of about 800 m above sea level going on two legs forth and back along the coast. The legs differed in the distance from the coastline, of 700 m and 2 km, respectively.</p><p>Reflectometry signal processing involves three data levels. Level (0): The raw data samples of Syntony front-end receiver. Level (1): The Delay-Doppler Map (DDM) of the correlated reflected signal and the carrier phase, from which geophysical information can be derived. And Level (2): height estimation (from signal correlation in delay and frequency domain) and roughness estimation (from signal amplitude).</p><p>By using the DDM and the carrier phase delay the sea state shall be assessed including the achievable precision and reliability of estimates. An additional aim is also to validate the configuration in terms of the used platform, antenna setup, and flight design.</p>

scholarly journals Dual-Satellite Lunar Global Navigation System Using Multi-Epoch Double-Differenced Pseudorange Observations

Aerospace ◽  
2020 ◽  
Vol 7 (9) ◽  
pp. 122
Author(s):  
Toshiki Tanaka ◽  
Takuji Ebinuma ◽  
Shinichi Nakasuka
Keyword(s):  
Digital Elevation Model ◽  
Lunar Surface ◽  
Navigation System ◽  
Satellite Navigation ◽  
Navigation Systems ◽  
Position Accuracy ◽  
Digital Elevation ◽  
Navigation Algorithms ◽  
Global Navigation ◽  
Elevation Model

In view of the upcoming missions to obtain resources from the lunar surface, it is essential to have highly-accurate navigation systems to locate surface vehicles in shadowed regions. In response, we propose a dual-satellite lunar navigation system that is based on a multi-epoch double-differenced pseudorange observations (MDPO) algorithm. We used multi-epoch observations in a new way that reduces the number of navigation satellites required. In addition, the double-differenced pseudorange is used in order to eliminate the bias effects of the satellite and user clocks that conventional dual-satellite navigation algorithms did not fully take into account. Furthermore, a pre-known lunar digital elevation model is used to reduce the number of observations. The theoretical behavior of the MDPO algorithm was confirmed by simulation and the results indicate that user position accuracy can be several tens of meters with 95% probability (2drms) within a one-minute observation.

scholarly journals Landslide site delineation from geometric signatures derived with the Hilbert–Huang transform for cases in Southern Taiwan

2020 ◽  
Vol 12 (1) ◽  
pp. 928-945
Author(s):  
Shun-Hsing Yang ◽  
Jyh-Jong Liao ◽  
Yi-Wen Pan ◽  
Peter Tian-Yuan Shih
Keyword(s):  
Large Scale ◽  
Global Climate ◽  
Terrain Analysis ◽  
Hilbert Huang Transform ◽  
Analysis Process ◽  
Digital Elevation ◽  
Main Scarp ◽  
Southern Taiwan ◽  
The Government ◽  
Elevation Model

AbstractLandslides are a frequently occurring threat to human settlements. Along with global climate change, the occurrence of landslides is the forecast to be even more frequent than before. Among numerous factors, topography has been identified as a correlated subject and from which hillslope landslide-prone areas could be analyzed. Geometric signatures, including statistical descriptors, topographic grains, etc., provide an analytical way to quantify terrain. Various published literature, fast Fourier transform, fractals, wavelets, and other mathematical tools were applied for this parameterization. This study adopts the Hilbert–Huang transform (HHT) method to identify the geomorphological features of a landslide from topographic profiles. The sites of the study are four “large-scale potential landslide areas” registered in the government database located in Meinong, Shanlin, and Jiasian in southern Taiwan. The topographic mapping was conducted with an airborne light detection and ranging instrument. The resolution of the digital elevation model is 1 m. Each topographic profile was decomposed into a number of intrinsic mode function (IMF) components. Terrain characterization was then performed with the spectrum resulting from IMF decomposition. This research found that the features of landslides, including main scarp-head, minor scarp, gully, and flank, have strong correspondence to the features in the IMF spectrum, mainly from the first and the second IMF components. The geometric signatures derived with HHT could contribute to the delineation of the landslide area in addition to other signatures in the terrain analysis process.

scholarly journals Hill slope terrain and land-use assessment using GIS and Remote Sensing techniques: A case of Pikhuwa sub-watershed in the Mid-hill, Nepal

2018 ◽  
Vol 6 ◽  
pp. 29-37
Author(s):  
Dil Kumar Rai ◽  
Furbe Lama
Keyword(s):  
Remote Sensing ◽  
Land Use ◽  
Global Climate ◽  
Land Use Pattern ◽  
Land Capability ◽  
Gis And Remote Sensing ◽  
Hill Slope ◽  
Digital Elevation ◽  
Remote Sensing Techniques ◽  
Elevation Model

Agriculture practice on hill-slope terrain depicts the sensitivity indicators of the vulnerability in terms of global climate change. The major aims of the present research are to assess the land-use pattern conditioned by existing hill-slope terrain based on different land capability class recommend by land resources mapping project, 1986 in the Pikhuwa sub-watershed of Mid-hills, Bhojpur, Nepal. An overall research data derived, processed and analyzed using Geographic Information System and Remote sensing tools and techniques. The land capability class, current land-use and digital elevation model with 30 meter spatial resolution have primarily considered as a major variable for spatial analysis. The analysis estimated about 33.68% individual area of overall agriculture patches have remained on above 30 degrees slope of the terrain topography, which denotes the condition of land-use is not suited technically based on land capability class and recommendation made by LRMP, 1986. In the sub-watershed, the current land-use condition on hill-slope is being much vulnerable due to the steep slope, poor slope terracing and unmanaged surface runoff during monsoon.

Optimal Processing of Information from Inertial and Satellite Navigation Systems by Analysis after Flight

2001 ◽  
Vol 56 (3) ◽  
pp. 13
Author(s):  
E. G. Kharin ◽  
V. G. Maslennikov ◽  
N. B. Vavilova ◽  
I. A. Kopylov ◽  
A. Ch. Staroverov
Keyword(s):  
Satellite Navigation ◽  
Navigation Systems ◽  
Optimal Processing ◽  
Satellite Navigation Systems

STUDY OF THE LANDSLIDE MORPHOLOGY BASED ON GNSS DATA AND AIRBORNE SOUNDING (ON THE EXAMPLE OF A SECTION OF THE PROTVA RIVER VALLEY)

2018 ◽  
Vol 12 (5-6) ◽  
pp. 50-57 ◽  
Author(s):  
I. S. Voskresensky ◽  
A. A. Suchilin ◽  
L. A. Ushakova ◽  
V. M. Shaforostov ◽  
A. L. Entin ◽  
...  
Keyword(s):  
Digital Elevation Model ◽  
Geodetic Network ◽  
Aerial Survey ◽  
River Valley ◽  
Ease Of Use ◽  
Digital Elevation ◽  
Loose Deposits ◽  
Positioning Method ◽  
Landslide Body ◽  
Elevation Model

To use unmanned aerial vehicles (UAVs) for obtaining digital elevation models (DEM) and digital terrain models (DTM) is currently actively practiced in scientific and practical purposes. This technology has many advantages: efficiency, ease of use, and the possibility of application on relatively small area. This allows us to perform qualitative and quantitative studies of the progress of dangerous relief-forming processes and to assess their consequences quickly. In this paper, we describe the process of obtaining a digital elevation model (DEM) of the relief of the slope located on the bank of the Protva River (Satino training site of the Faculty of Geography, Lomonosov Moscow State University). To obtain the digital elevation model, we created a temporary geodetic network. The coordinates of the points were measured by the satellite positioning method using a highprecision mobile complex. The aerial survey was carried out using an unmanned aerial vehicle from a low altitude (about 40–45 m). The processing of survey materials was performed via automatic photogrammetry (Structure-from-Motion method), and the digital elevation model of the landslide surface on the Protva River valley section was created. Remote sensing was supplemented by studying archival materials of aerial photography, as well as field survey conducted immediately after the landslide. The total amount of research results made it possible to establish the causes and character of the landslide process on the study site. According to the geomorphological conditions of formation, the landslide refers to a variety of landslideslides, which are formed when water is saturated with loose deposits. The landslide body was formed with the "collapse" of the blocks of turf and deluvial loams and their "destruction" as they shifted and accumulated at the foot of the slope.

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