Hyperspectral Imaging Tera Hertz System for Soil Analysis: Initial Results

dc.contributor.authorDworak, Volker
dc.contributor.authorMahns, Benjamin
dc.contributor.authorSelbeck, Jörn
dc.contributor.authorGebbers, Robin
dc.contributor.authorWeltzien, Cornelia
dc.date.accessioned2020-11-13T12:28:16Z
dc.date.available2020-11-13T12:28:16Z
dc.date.issued2020-10-03
dc.date.updated2020-11-11T14:46:29Z
dc.description.abstractAnalyzing soils using conventional methods is often time consuming and costly due to their complexity. These methods require soil sampling (e.g., by augering), pretreatment of samples (e.g., sieving, extraction), and wet chemical analysis in the laboratory. Researchers are seeking alternative sensor-based methods that can provide immediate results with little or no excavation and pretreatment of samples. Currently, visible and infrared spectroscopy, electrical resistivity, gamma ray spectroscopy, and X-ray spectroscopy have been investigated extensively for their potential utility in soil sensing. Little research has been conducted on the application of THz (Tera Hertz) spectroscopy in soil science. The Tera Hertz band covers the frequency range between 100 GHz and 10 THz of the electromagnetic spectrum. One important feature of THz radiation is its correspondence with the particle size of the fine fraction of soil minerals (clay < 2 µm to sand < 2 mm). The particle size distribution is a fundamental soil property that governs soil water and nutrient content, among other characteristics. The interaction of THz radiation with soil particles creates detectable Mie scattering, which is the elastic scattering of electromagnetic waves by particles whose diameter corresponds approximately to the wavelength of the radiation. However, single-spot Mie scattering spectra are difficult to analyze and the understanding of interaction between THz radiation and soil material requires basic research. To improve the interpretation of THz spectra, a hyperspectral imaging system was developed. The addition of the spatial dimension to THz spectra helps to detect relevant features. Additionally, multiple samples can be scanned in parallel and measured under identical conditions, and the high number of data points within an image can improve the statistical accuracy. Technical details of the newly designed hyperspectral imaging THz system working from 250 to 370 GHz are provided. Results from measurements of different soil samples and buried objects in soil demonstrated its performance. The system achieved an optical resolution of about 2 mm. The sensitivity of signal damping to the changes in particle size of 100 µm is about 10 dB. Therefore, particle size variations in the µm range should be detectable. In conclusion, automated hyperspectral imaging reduced experimental effort and time consumption, and provided reliable results because of the measurement of hundreds of sample positions in one run. At this stage, the proposed setup cannot replace the current standard laboratory methods, but the present study represents the initial step to develop a new automated method for soil analysis and imaging.en
dc.description.sponsorshipBMBF, 031B0513A, BonaRes (Modul A, Phase 2): I4S - Integriertes System zum ortsspezifischen Management der Bodenfruchtbarkeit, Teilprojekt A: Projektkoordination sowie Entwicklung von Sensorplattformen, UV-, Vis-NIR- und THz-Sensorenen
dc.identifier.eissn1424-8220
dc.identifier.urihttps://depositonce.tu-berlin.de/handle/11303/11938
dc.identifier.urihttp://dx.doi.org/10.14279/depositonce-10829
dc.language.isoenen
dc.rights.urihttps://creativecommons.org/licenses/by/4.0/en
dc.subject.ddc620 Ingenieurwissenschaften und zugeordnete Tätigkeitende
dc.subject.otherhyperspectral imagingen
dc.subject.otherMie scatteringen
dc.subject.othersoil imagingen
dc.subject.othersoil sensingen
dc.titleHyperspectral Imaging Tera Hertz System for Soil Analysis: Initial Resultsen
dc.typeArticleen
dc.type.versionpublishedVersionen
dcterms.bibliographicCitation.articlenumber5660en
dcterms.bibliographicCitation.doi10.3390/s20195660en
dcterms.bibliographicCitation.issue19en
dcterms.bibliographicCitation.journaltitleSensorsen
dcterms.bibliographicCitation.originalpublishernameMDPIen
dcterms.bibliographicCitation.originalpublisherplaceBaselen
dcterms.bibliographicCitation.volume20en
tub.accessrights.dnbfreeen
tub.affiliationFak. 5 Verkehrs- und Maschinensysteme>Inst. Maschinenkonstruktion und Systemtechnik>FG Agromechatronikde
tub.affiliation.facultyFak. 5 Verkehrs- und Maschinensystemede
tub.affiliation.groupFG Agromechatronikde
tub.affiliation.instituteInst. Maschinenkonstruktion und Systemtechnikde
tub.publisher.universityorinstitutionTechnische Universität Berlinen
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