scholarly journals Search and recovery of aircraft parts in ice-sheet crevasse fields using airborne and in situ geophysical sensors

2020 ◽  
Vol 66 (257) ◽  
pp. 496-508
Author(s):  
Kenneth D. Mankoff ◽  
Dirk van As ◽  
Austin Lines ◽  
Thue Bording ◽  
Joshua Elliott ◽  
...  
Keyword(s):  
Ground Penetrating Radar ◽  
Autonomous Vehicle ◽  
Synthetic Aperture ◽  
Search Area ◽  
Surrounding Structure ◽  
Drifting Snow ◽  
Field Campaigns ◽  
Fall Arrest ◽  
Ground Penetrating

On 30 September 2017, an Air France Airbus A380-800 suffered a failure of its fourth engine while over Greenland. This failure resulted in the loss of the engine fan hub, fan blades and surrounding structure. An initial search recovered 30 pieces of light debris, but the primary part of interest, a ~220 kg titanium fan hub, was not recovered because it had a different fall trajectory than the light debris, impacted into the ice-sheet's snow surface, and was quickly covered by drifting snow. Here we describe the methods used for the detection of the fan hub and details of the field campaigns. The search area included two crevasse fields of at least 50 snow-covered crevasses 1 to ~30 m wide with similar snow bridge thicknesses. After 21 months and six campaigns, using airborne synthetic aperture radar, ground-penetrating radar, transient electromagnetics and an autonomous vehicle to survey the crevasse fields, the fan hub was found within ~1 m of a crevasse at a depth of ~3.3 to 4 m and was excavated with shovels, chain saws, an electric winch, sleds and a gasoline heater, by workers using fall-arrest systems.

scholarly journals Identifying Spatial and Temporal Variations in Concrete Bridges with Ground Penetrating Radar Attributes

2021 ◽  
Vol 13 (9) ◽  
pp. 1846
Author(s):  
Vivek Kumar ◽  
Isabel M. Morris ◽  
Santiago A. Lopez ◽  
Branko Glisic
Keyword(s):  
Compressive Strength ◽  
Ground Penetrating Radar ◽  
Material Properties ◽  
Temporal Variations ◽  
Concrete Bridges ◽  
Spatial And Temporal Variation ◽  
Reflected Waves ◽  
Ground Penetrating ◽  
Over Time

Estimating variations in material properties over space and time is essential for the purposes of structural health monitoring (SHM), mandated inspection, and insurance of civil infrastructure. Properties such as compressive strength evolve over time and are reflective of the overall condition of the aging infrastructure. Concrete structures pose an additional challenge due to the inherent spatial variability of material properties over large length scales. In recent years, nondestructive approaches such as rebound hammer and ultrasonic velocity have been used to determine the in situ material properties of concrete with a focus on the compressive strength. However, these methods require personnel expertise, careful data collection, and high investment. This paper presents a novel approach using ground penetrating radar (GPR) to estimate the variability of in situ material properties over time and space for assessment of concrete bridges. The results show that attributes (or features) of the GPR data such as raw average amplitudes can be used to identify differences in compressive strength across the deck of a concrete bridge. Attributes such as instantaneous amplitudes and intensity of reflected waves are useful in predicting the material properties such as compressive strength, porosity, and density. For compressive strength, one alternative approach of the Maturity Index (MI) was used to estimate the present values and compare with GPR estimated values. The results show that GPR attributes could be successfully used for identifying spatial and temporal variation of concrete properties. Finally, discussions are presented regarding their suitability and limitations for field applications.

IN-SITU CASSAVA ROOT SIZE MEASUREMENT USING GROUND PENETRATING RADAR (GPR)

2018 ◽  
Author(s):  
Timothy H. Larson ◽  
Riley J. Balikian ◽  
Ursula Ruiz-Vera ◽  
Donald Ort
Keyword(s):  
Ground Penetrating Radar ◽  
Size Measurement ◽  
Cassava Root ◽  
Ground Penetrating ◽  
Root Size

scholarly journals Accounting for Surface Roughness Scattering in the Characterization of Forest Litter with Ground-Penetrating Radar

2019 ◽  
Vol 11 (7) ◽  
pp. 828
Author(s):  
Frédéric André ◽  
François Jonard ◽  
Mathieu Jonard ◽  
Harry Vereecken ◽  
Sébastien Lambot
Keyword(s):  
Surface Roughness ◽  
Ground Penetrating Radar ◽  
Land Surface ◽  
Forest Litter ◽  
Relative Dielectric Permittivity ◽  
In Situ Experiment ◽  
In Situ Experiments ◽  
Ground Penetrating

Accurate characterization of forest litter is of high interest for land surface modeling and for interpreting remote sensing observations over forested areas. Due to the large spatial heterogeneity of forest litter, scattering from litter layers has to be considered when sensed using microwave techniques. Here, we apply a full-waveform radar model combined with a surface roughness model to ultrawideband ground-penetrating radar (GPR) data acquired above forest litter during controlled and in situ experiments. For both experiments, the proposed modeling approach successfully described the radar data, with improvements compared to a previous study in which roughness was not directly accounted for. Inversion of the GPR data also provided reliable estimates of the relative dielectric permittivity of the recently fallen litter (OL layer) and of the fragmented litter in partial decomposition (OF layer) with, respectively, averaged values of 1.35 and 3.8 for the controlled experiment and of 3.9 and 7.5 for the in situ experiment. These results show the promising potentialities of GPR for efficient and non-invasive characterization of forest organic layers.

scholarly journals Spatially Extensive Ground‐Penetrating Radar Snow Depth Observations During NASA's 2017 SnowEx Campaign: Comparison With In Situ, Airborne, and Satellite Observations

2019 ◽  
Vol 55 (11) ◽  
pp. 10026-10036 ◽  
Author(s):  
Daniel McGrath ◽  
Ryan Webb ◽  
David Shean ◽  
Randall Bonnell ◽  
Hans‐Peter Marshall ◽  
...  
Keyword(s):  
Ground Penetrating Radar ◽  
Snow Depth ◽  
Satellite Observations ◽  
Ground Penetrating

GPR attenuation and its numerical simulation in 2.5 dimensions

Geophysics ◽  
1997 ◽  
Vol 62 (2) ◽  
pp. 403-414 ◽  
Author(s):  
Tong Xu ◽  
George A. McMechan
Keyword(s):  
Time Domain ◽  
Ground Penetrating Radar ◽  
Finite Difference Time Domain ◽  
Superposition Method ◽  
Frequency Data ◽  
Buried Pipe ◽  
Ground Penetrating ◽  
Cole Model ◽  
Difference Time

Modeling of ground‐penetrating radar (GPR) data in 2.5 dimensions is implemented by superposition of 2-D finite‐difference, time‐domain solutions of Maxwell's equations for different horizontal wavenumbers. Dielectric, magnetic, and conductive losses are included in a single formulation. Attenuations associated with dielectric and magnetic relaxations are introduced by superposition of Debye functions at a set of relaxation frequencies and using memory variables to replace convolutions between the field variables and the decay functions. Better fits to data may always be obtained using the superposition method than by the Cole‐Cole model. Good fits to both loss‐tangent versus frequency data from lab measurements, and to 500 and 900 MHz field GPR profiles of a buried pipe and the surrounding layers, demonstrate the flexibility and viability of the modeling algorithm. Discrepancies between lab and in‐situ measurements may be attributed to scale differences and local variations that make lab samples less representative of the site than the GPR profile.

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