Detection Of Amplitude Changes Research Articles

Mapping and Pre- and Post-Failure Analyses of the April 2019 Kantutani Landslide in La Paz, Bolivia, Using Synthetic Aperture Radar Data

Urban landslides have brought challenges to developing countries undergoing urbanization. Rapid approaches to assess ground deformation are required when facing the challenge of insufficient geological survey methods. Additionally, it is indeed a challenge to map landslide-affected areas, especially precipitation-induced landslides, through optical remote sensing methods. This study applied SAR change detection methods to map the slope failure event of the San Jorge Kantutani landfill site in La Paz, Bolivia, which occurred in April 2019, and Multi-Temporal Synthetic Aperture Radar Interferometry (MTInSAR) methods to assess pre- and post-failure ground stability related to this event. We found that the amplitude information of high-resolution COSMO-SkyMed SAR imagery and its texture information can be very useful in landslide mapping, especially in situations in which optical images are not available because of complex meteorological conditions and the similar spectral characteristics between the original land cover and landslide deposits. The MTInSAR analyses found that there was already significant deformation of more than 50 mm/year along the slope direction over this site before the landslide, and such deformation could be clearly discriminated from the surrounding environment. After the landslide event and the remobilization of the landslide deposit, the slope still shows a deformation velocity of more than 30 mm/year. The SAR amplitude change detection and MTInSAR fully exploited the SAR data in landslide studies and were useful in back analyzing the occurred landslides; this could be a good method for monitoring the ground stability of La Paz or even on a national scale over the long term for reducing the catastrophic effects of geological hazards in this landslide-prone city.

Synergic use of Sentinel-1 and Sentinel-2 data for automatic detection of earthquake-triggered landscape changes: A case study of the 2016 Kaikoura earthquake (Mw 7.8), New Zealand

Earthquakes can trigger numerous landslides and cause other significant changes in the landscape over large areas. This study presents a new processing scheme combining radar (Copernicus Sentinel-1) and optical satellite data (Copernicus Sentinel-2) to quickly and easily map landscape changes such as landslides, coastal uplift and changes in water bodies caused by a severe event such as an earthquake. The processing scheme has been tested for the 2016 Kaikoura earthquake (Mw 7.8), New Zealand, which impacted vast and mostly inaccessible areas, causing hundreds of landslides. The workflow combines the following change-detection methods: i) Sentinel-1 amplitude change detection ii) Sentinel-2-based detection of non-vegetated areas that occurred after the event using the atmospherically resistant vegetation index (ARVI). To get a more complex view of the surface changes caused by the Kaikoura earthquake, the available online services and tools were further tested (open source via the European Space Agency) allowing automatic detection of vertical displacements and deformations. It was concluded, that the above-mentioned approaches facilitated the assessment of earthquake-triggered changes in a comprehensive manner. The methodology is an example of how to detect earthquake landscape changes in an automatic and rapid manner. The new processing scheme for the synergic use of Sentinel-1 and Sentinel-2 data has high potential to be used for operational and scientific purposes, since it relies on globally available, free data and provides high spatial and temporal resolution. The results can be obtained and made available only a few days after an event, therefore providing significant insights into earthquake impact assessment and may also be helpful for prioritizing field work.

Detection of downhole incidents for complex geological drilling processes using amplitude change detection and dynamic time warping

Geological drilling process is operating under complex geological conditions, which may lead to a high risk of downhole incidents and thus compromise the drilling efficiency. To achieve prompt detection of downhole incidents and prevent them from developing to serious drilling accidents, this paper proposes a new data-driven detection method for downhole incidents based on the amplitude change detection and dynamic time warping. Two major phases are involved: the change monitoring phase detects whether there is any significant change in the drilling signals and extracts variational trend features by linear fitting and amplitude change detection; the incident detection phase determines if the cause of a change is a normal switching or a downhole incident by similarity analysis based on the dynamic time warping and the density-based spatial clustering. Industrial case studies show that the proposed method achieves good performance in downhole incidents detection for geological drilling processes.

Satellite-based assessment of grassland yields

Abstract. Cutting date and frequency are important parameters determining grassland yields in addition to the effects of weather, soil conditions, plant composition and fertilisation. Because accurate and area-wide data of grassland yields are currently not available, cutting frequency can be used to estimate yields. In this project, a method to detect cutting dates via surface changes in radar images is developed. The combination of this method with a grassland yield model will result in more reliable and regional-wide numbers of grassland yields. For the test-phase of the monitoring project, a study area situated southeast of Munich, Germany, was chosen due to its high density of managed grassland. For determining grassland cutting robust amplitude change detection techniques are used evaluating radar amplitude or backscatter statistics before and after the cutting event. CosmoSkyMed and Sentinel-1A data were analysed. All detected cuts were verified according to in-situ measurements recorded in a GIS database. Although the SAR systems had various acquisition geometries, the amount of detected grassland cut was quite similar. Of 154 tested grassland plots, covering in total 436 ha, 116 and 111 cuts were detected using CosmoSkyMed and Sentinel-1A radar data, respectively. Further improvement of radar data processes as well as additional analyses with higher sample number and wider land surface coverage will follow for optimisation of the method and for validation and generalisation of the results of this feasibility study. The automation of this method will than allow for an area-wide and cost efficient cutting date detection service improving grassland yield models.

Amplitude Change Detection with ENVISAT ASAR to Image the Cultural Landscape of the Nasca Region, Peru

ABSTRACTSynthetic aperture radar (SAR) amplitude information from ENVISAT C‐band advanced SAR (ASAR) data was used to analyse the cultural landscape of the Nasca region, southern Peru. A multispatial environmental analysis was performed over the whole drainage basin of the Rio Grande, by extracting the radar backscattering coefficient (σ0) of both natural and anthropogenic features between 2003 and 2005. Co‐registration of the ASAR scenes to a single master resulted in precisions of less than 0.1 pixels along both the range and azimuth directions. Four different products were generated based on the co‐registered ASAR stack: (i) temporally averaged radar signatures of the targets between 2003 and 2005; (ii) time series of spatially averaged radar signatures within selected areas of interest; (iii) amplitude change detection products based on (iii) image ratios and (iv) RGB colour composites between different scenes. Comparisons of annual and seasonal records through amplitude change detection maps highlighted σ0 changes over the floodplains of the Rio Ingenio and Rio Nazca, which correlate well with evidence from Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) data acquired in 2003, 2004 and 2007. Inferences about land use and soil conditions were retrieved from the σ0 change patterns, thereby proving the capability of this approach to support landscape evolution studies, even with SAR imagery of medium resolution (~30 m). Our results also demonstrated actual potential for monitoring mass movements and land surface processes, to assess the susceptibility of archaeological heritage and cultural landscape to natural hazards. Copyright © 2013 John Wiley & Sons, Ltd.

Prospection and Monitoring of the Archaeological Heritage of Nasca, Peru, with ENVISAT ASAR

ABSTRACTThe processing method based on synthetic aperture radar (SAR) amplitude information presented by Cigna et al. (2013, this issue) was used to extract the backscattering coefficient (σ0) from ENVISAT advanced SAR (ASAR) scenes to investigate the archaeological heritage of the Nasca region, southern Peru. Average backscattering and σ0 time series in 2003–2007 were obtained for some of the most famous groups of the Nazca Lines, as well as for the adobe structures of the Ceremonial Centre of Cahuachi, and allowed the recognition of anthropogenic features on arid and bare soil. Despite the expected constraints due to the medium spatial resolution of the ASAR scenes (~30 m), some features related to the Nasca ancient aqueduct systems (puquios) were detected, and water level changes were inferred from amplitude change detection maps and σ0 time series. The SAR‐based prospection results were also compared with a vegetation index derived from Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) data for 2003, 2004 and 2007. The changes observed over Cahuachi and the neighbouring archaeological mounds are then discussed in light of the recent conservation history of the site and the contemporary archaeological excavations. The research opens interesting perspectives for routine use of SAR data for purposes of archaeological prospection and condition monitoring in (semi‐)arid and desert regions. Copyright © 2013 John Wiley & Sons, Ltd.

Assessment of the amplitude of oscillations associated with high-frequency components of physiological tremor: impact of loading and signal differentiation

The goal of this study was accurate quantification of the amplitude of high-frequency components of physiological tremor (PT) in units of displacement, velocity, and acceleration. In addition, changes of amplitude with finger loading were compared within specific frequency bands. Index finger tremor was measured for 20 healthy subjects using a high-resolution laser, simultaneously with an accelerometer, under two conditions, unloaded and loaded (70 g). By use of an accurate filtering technique, oscillations within six predetermined frequency bands were isolated. Results showed that overall mean tremor amplitude under the unloaded condition was 0.0973 mm in displacement units, 4.525 mm s(-1) in velocity units, and 301.526 mm s(-2) in acceleration units. Although the mean amplitude of oscillations located within the 16.5-30 Hz band was 0.009 mm and represented only 10% of total tremor amplitude, amplitude of acceleration within the 16.5-30 Hz band was 191 mm s(-2) and represented 60% of total acceleration amplitude. Mean amplitude increased significantly with loading (displacement, t=-2.67, P=0.015; velocity, t=-4.33, P=0.000; acceleration, t=-3.48, P=0.002) but the magnitude of that change was different in each frequency band and its relative importance depended on the level of signal differentiation. Velocity was the only measure that retained sensitivity to changes in amplitude with loading in the low and high-frequency components of PT. In conclusion, this study provides, for the first time, accurate quantification of the amplitude of oscillation of high-frequency components of PT. In addition, it provides clear evidence that the velocity of tremor oscillation is more suitable for detection of the impact of finger loading because it enables detection of amplitude changes in both the low and high-frequency components of PT.

Monitoring dynamic processes with alphanumeric and graphic displays

Three experiments assessed the relative efficiency of graphic and tabular displays for detecting changes in periodic sine functions, simulating a dynamic process. In all three experiments, line graphs had an advantage over tables for response times, for correct detections and identifications, and for false alarms. However, this advantage depended on the type of change that indicated a malfunction. The largest difference between the displays was evident for the detection of changes in a function's frequency and smaller differences were found for the detection of changes in amplitude and intercept. Results also indicated that participants adapted their detection methods to the types of possible changes. The findings demonstrate the value of graphic displays for process control and substantiate the claim that graphic displays have an advantage when the displayed information has inherent structure and when the task requires the use of this structure. In addition, task performance was the subject of adaptive changes, which depend on the context in which the task is performed.

Comparison of SAR amplitude vs. coherence flood detection methods - a GIS application

Flood area detection from multipass Synthetic Aperture Radar (SAR) data can be performed via amplitude change detection techniques. These methods allow flooded zones to be discriminated only when they are flooded at the time of the second passage, and not at the time of the first one. Coherence derived from multipass SAR interferometry can be used instead, as an indicator of changes in the electromagnetic scattering behaviour of the surface, thus potentially revealing all the areas affected by the flood event at any time between the two passes. The paper presents a prototype application of such techniques, that is, a flood map obtained from ERS-1/2 data taken over Beziers (Southern France), through proper thresholding of a combination of amplitude and coherence information. Produced in the framework of an ESA project, the map consists of a DXF vector file which can be imported directly into most commercial GIS software.

Physiological correlates of the ‘‘mean-term’’ auditory adaptation

In psychophysics, adaptation is defined usually as a decline of loudness of steady stimulus as a function of time. It occurs over periods ranging from seconds to minutes. Recent psychophysical data show that during a ‘‘mean-term’’ adaptation period (the first 30 seconds of the sound) the detection of amplitude changes considerably improves. Physiological correlates of ‘‘mean-term’’ adaptation in single units located in different regions (cochlear nucleus, superior olive, torus semicircularis) of the auditory system of the immobilized frog Rana temporaria are explored. Driven responses to long-duration pure tones and AM tones decreased over time periods ranging from milliseconds to minutes. The adaptation increased at the upper levels of the auditory system. The response to pure tone stimuli declined more rapidly than the response to AM tones. For AM stimuli the adaptation increased as the modulation depth decreased. The considerable enhancement of the phase locking to the sound envelope could be observed during the first 10–15 s of the AM tones with low modulation indexes. The effect of phase-locking enhancement during the mean-term adaptation matched some psychoacoustical findings. [Work supported by the RFBR.]

Detection of amplitude changes in the presence of adjacent stimulation by cochlear implant recipients

Recent results [Hawks et al., in revision for Ear Hear.] suggest that disambiguation of neighboring lax vowels by cochlear implant (CI) recipients using the spectral peak (SPEAK) speech coding strategy may be hindered by the lack of perceptually significant differences in the coding of F1 and F2 as represented in the electrode activation patterns. Since multiple adjacent electrodes are activated when coding these spectral prominences, it is important to know how much activation is necessary to elicit the percept of a spectral peak in the presence of adjacent stimulation. To investigate this issue, CI recipients and normal hearing adults were compared on a detection task. Continua of three-tone complexes were constructed with tone frequencies equal to the centers of the frequency bands encoded by three adjacent electrodes in the F1 region and again for the F2 region. Stimuli were varied in intensity of the center tone, incremented both above and below a fixed level for the bounding tones. An adaptive procedure was used to estimate subjects’ thresholds for detection of a change in center tone amplitude from the pedestal level. Results will be discussed in terms of their significance to CI processor coding strategies of spectral information for vowels.

Biomuse: Musical performance generated by human bioelectric signals

A new type of musical instrument is described which utilizes bioelectric signals to drive a keyboard synthesizer via standard musical instrument digital interface (MIDI) code. Electrical activity from muscle (EMG), brain (EEG), heart (EKG), and eye (EOG) is detected by small disk electrodes on the skin, analyzed by a digital signal processor, and used to control sound generation from the synthesizer. Signal processing algorithms are designed to extract useful control parameters from the given physiological signals. For instance, detection of amplitude changes in the EMG and spectral changes in the EEG can be used to generate MIDI commands. Applications for the device are discussed, such as dance generated music, musician self-mixed performances, and music production by the handicapped.

Matched transfer characteristics of single units in a compound slit sense organ

The transfer characteristics of the lyriform slit sense organ HS8 on the leg tibia ofCupiennius salei Keys. (Fig. 1) were investigated by electrophysiological experiments. The organ is made up of 7 slits. It was stimulated by deflecting the metatarsus toward the fixed tibia. The responses of the constituent slits were recorded individually. 1. The step responses of the 2nd to the 4th slits can be described bypower functions (t−k), where (t) is the time and (k) is a constant between 0 and 1 (Figs. 6, 8). This means that the sensilla take a position between a frequency independent system (displacement receptor) and a first order differentiator (velocity receptor). The standard deviations of the receptor responses coincide intra-individually and inter-individually (Fig. 5). 2. Thelinearity of the system was demonstrated using the second slit as an example: a) The slit responds proportionally to step amplitudes from 0.1° to 0.4°; (k) varies only slightly from 0.32 to 0.38 (Fig. 6). b) For stimulus frequencies of 0.01 Hz to 8 Hz the transfer functions calculated from the step response and those estimated from sinewave stimulation match well (Fig. 7). c) For stimulus frequencies of 0.01 Hz to 100 Hz the number of spikes/stimulus sinewave is nearly the same, no matter whether calculated from the step responses or measured by sinewave stimuli (Fig. 12). 3. Comparing the results for the 3 slit sensilla investigated (of a total of 7) the following conclusions are drawn: a) Thehigh-pass characteristic (exponentk) of the sensilla increases from the 2nd to the 4th slit, while the relative gain decreases (Fig. 8). b) Thebandwidth of the sensilla decreases according to decreasing sensitivity from slit 2 to slit 4, since the maximal stimulating frequency which can be encoded unequivocally (three spikes/stimulating sinewave) is less than 20–30 Hz for all the slits investigated (Fig. 12). c) Thefrequency-dependent threshold curves confirm the calculated transfer functions. For a stimulus frequency of 1 Hz the thresholds of the 2nd to the 4th slit are ca. 0.025°, 0.25° and 1.25° (deflection of the metatarsus), at 100 Hz 0.01°, 0.05° and 0.125° (extrapolated). From 0.01 Hz to 100 Hz no tuning of different slits to different “resonant frequencies” was seen (Figs. 11, 12). d) The characteristic curves (input amplitude vs. output-spike frequency) of the 2nd to 4th slit show an overlap of the amplitude ranges to which the sensilla respond; their linear parts, however, are linked up. This results in an extension of both the effective linear amplitude range and the range of precise detection of amplitude changes. The upper and lower limits of the linear parts of the characteristic curves depend on the stimulus frequency (Figs. 9, 10, 14, Eq. 6). 7. The receptor system can be described as consisting of a linear part with high-pass character plus a nonlinear rectifying part with a threshold. The linear part precedes the nonlinear one (Figs. 15, 16).