{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,2,2]],"date-time":"2026-02-02T22:19:27Z","timestamp":1770070767376,"version":"3.49.0"},"reference-count":59,"publisher":"MDPI AG","issue":"9","license":[{"start":{"date-parts":[[2019,5,7]],"date-time":"2019-05-07T00:00:00Z","timestamp":1557187200000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100009882","name":"Regione Lombardia","doi-asserted-by":"publisher","award":["145427"],"award-info":[{"award-number":["145427"]}],"id":[{"id":"10.13039\/501100009882","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Remote Sensing"],"abstract":"<jats:p>Soil morphology plays a fundamental role in the vertical and lateral movements of solutes and water transport, providing knowledge regarding spatial distribution of its textural properties and subsurface dynamics. In this framework, the measured values of electrical conductivity are able to reveal the heterogeneity of soil that is present in a particular agricultural field and they are affected by more than one important physical characteristic: soil texture, organic matter, moisture content, and the depth of the clay pan. In the microwave region, these dynamics are known to exhibit a frequency dependent behaviour. This study explores the application of a Step Frequency Continuous Wave Ground Penetrating Radar (SFCW GPR) to shed light on the practical impact that these dependencies have on the imaging results, not only regarding the electrical characterisation of the subsurface morphology, but also in its correct interpretation. This information is of notable importance for determining water-use efficiency and planning precision-agriculture programs. The results clearly show visible and significant fluctuations of the amplitude levels, depending on the considered central frequency, demonstrating that the frequency dependence of electromagnetic properties of heterogeneous soil are significant and cannot be ignored if the aim is to properly define the subsurface attributes. The measurements also suggest that correlating the delineated variations might help in the identification of extended features and the classification of areas that possess similar properties in order to increase the confidence in monitoring soil resources.<\/jats:p>","DOI":"10.3390\/rs11091075","type":"journal-article","created":{"date-parts":[[2019,5,9]],"date-time":"2019-05-09T08:19:59Z","timestamp":1557389999000},"page":"1075","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":23,"title":["Step-Frequency Ground Penetrating Radar for Agricultural Soil Morphology Characterisation"],"prefix":"10.3390","volume":"11","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-6626-7109","authenticated-orcid":false,"given":"Federico","family":"Lombardi","sequence":"first","affiliation":[{"name":"Department of Civil and Environmental Engineering, Politecnico di Milano, Piazza Leonardo da Vinci 32, 20133 Milan, Italy"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-6660-2790","authenticated-orcid":false,"given":"Maurizio","family":"Lualdi","sequence":"additional","affiliation":[{"name":"Department of Civil and Environmental Engineering, Politecnico di Milano, Piazza Leonardo da Vinci 32, 20133 Milan, Italy"}]}],"member":"1968","published-online":{"date-parts":[[2019,5,7]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"97","DOI":"10.1016\/j.enggeo.2007.03.006","article-title":"Effects of spatial variability of soil properties on slope stability","volume":"92","author":"Cho","year":"2007","journal-title":"Eng. Geol."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"241","DOI":"10.1016\/j.still.2017.07.015","article-title":"Spatial variability of soil properties and cereal yield in a cultivated field on sandy soil","volume":"174","author":"Usowicz","year":"2017","journal-title":"Soil Tillage Res."},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"285","DOI":"10.1111\/sum.12110","article-title":"Spatial and vertical analysis of soil properties in a Mediterranean vineyard soil","volume":"30","author":"Unamunzaga","year":"2014","journal-title":"Soil Use Manag."},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"256","DOI":"10.1016\/j.geoderma.2015.05.017","article-title":"Soil mapping, classification, and pedologic modeling: History and future directions","volume":"264","author":"Brevik","year":"2016","journal-title":"Geoderma"},{"key":"ref_5","unstructured":"Rossel, R.V., Adamchuk, V.I., Sudduth, K.A., McKenzie, N.J., and Lobsey, C. (2010). Proximal soil sensing: An effective approach for soil measurements in space and time. Advances in Agronomy, Springer. [1st ed.]."},{"key":"ref_6","doi-asserted-by":"crossref","unstructured":"Allred, B., Daniels, J.J., and Ehsani, M.R. (2008). Handbook of Agricultural Geophysics, CRC Press. [1st ed.].","DOI":"10.1201\/9781420019353"},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"31","DOI":"10.1190\/1.1444910","article-title":"Engineering and environmental geophysics at the millennium","volume":"66","author":"Steeples","year":"2001","journal-title":"Geophysics"},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"71","DOI":"10.1016\/j.compag.2004.03.002","article-title":"On-the-go soil sensors for precision agriculture","volume":"44","author":"Adamchuk","year":"2004","journal-title":"Comput. Electron. Agric."},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"29","DOI":"10.1007\/s11119-014-9381-6","article-title":"Three-dimensional digital soil mapping of agricultural fields by integration of multiple proximal sensor data obtained from different sensing methods","volume":"16","author":"Piikki","year":"2015","journal-title":"Precis. Agric."},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"4026","DOI":"10.3390\/rs70404026","article-title":"Evaluating multispectral images and vegetation indices for precision farming applications from UAV images","volume":"7","author":"Candiago","year":"2015","journal-title":"Remote Sens."},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"135","DOI":"10.1016\/j.jappgeo.2015.03.009","article-title":"Improved estimation of soil clay content by the fusion of remote hyperspectral and proximal geophysical sensing","volume":"116","author":"Ciampalini","year":"2015","journal-title":"J. Appl. Geophys."},{"key":"ref_12","doi-asserted-by":"crossref","unstructured":"Castrignan\u00f2, A., Buttafuoco, G., Quarto, R., Vitti, C., Langella, G., Terribile, F., and Venezia, A. (2017). A combined approach of sensor data fusion and multivariate geostatistics for delineation of homogeneous zones in an agricultural field. Sensors, 17.","DOI":"10.3390\/s17122794"},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"254","DOI":"10.1016\/j.compag.2016.04.016","article-title":"Use of corn height measured with an acoustic sensor improves yield estimation with ground based active optical sensors","volume":"124","author":"Sharma","year":"2016","journal-title":"Comput. Electron. Agric."},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"117","DOI":"10.1016\/j.geoderma.2012.08.028","article-title":"An approach for delineating homogeneous zones by using multi-sensor data","volume":"199","author":"Rinaldi","year":"2013","journal-title":"Geoderma"},{"key":"ref_15","doi-asserted-by":"crossref","unstructured":"Agapiou, A., Lysandrou, V., and Hadjimitsis, D. (2017). Optical remote sensing potentials for looting detection. Geosciences, 7.","DOI":"10.3390\/geosciences7040098"},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"1063","DOI":"10.2136\/vzj2010.0004","article-title":"A generalized frequency domain reflectometry modeling technique for soil electrical properties determination","volume":"9","author":"Minet","year":"2010","journal-title":"Vadose Zone J."},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"182","DOI":"10.1016\/j.measurement.2013.11.051","article-title":"Effect of time-domain reflectometry probe location on soil moisture measurement during wetting and drying processes","volume":"49","author":"Pastuszka","year":"2014","journal-title":"Measurement"},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"531","DOI":"10.1111\/j.1365-2478.1989.tb02221.x","article-title":"Ground Penetrating Radar for high resolution mapping of soil and rock stratigraphy","volume":"37","author":"Davis","year":"1989","journal-title":"Geophys. Prosp."},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"73","DOI":"10.3997\/1873-0604.2014036","article-title":"Utilities detection through the sum of orthogonal polarization in 3D georadar surveys","volume":"13","author":"Lualdi","year":"2015","journal-title":"Near Surf. Geophys."},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"58","DOI":"10.1016\/j.ndteint.2017.04.002","article-title":"A review of Ground Penetrating Radar application in civil engineering: A 30-year journey from Locating and Testing to Imaging and Diagnosis","volume":"96","author":"Lai","year":"2018","journal-title":"NDT E Int."},{"key":"ref_21","doi-asserted-by":"crossref","unstructured":"Daniels, D.J. (2004). Ground Penetrating Radar, The Institution of Electrical Engineers. [2nd ed.].","DOI":"10.1049\/PBRA015E"},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"55","DOI":"10.1016\/j.geoderma.2013.02.010","article-title":"Off-and on-ground GPR techniques for field-scale soil moisture mapping","volume":"200","author":"Ardekani","year":"2013","journal-title":"Geoderma"},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"560","DOI":"10.1016\/j.geoderma.2013.08.035","article-title":"Soil layering and preferential flow impacts on seasonal changes of GPR signals in two contrasting soils","volume":"213","author":"Zhang","year":"2014","journal-title":"Geoderma"},{"key":"ref_24","doi-asserted-by":"crossref","first-page":"623","DOI":"10.3997\/1873-0604.2014017","article-title":"Estimation of the near surface soil water content during evaporation using air-launched ground-penetrating radar","volume":"12","author":"Moghadas","year":"2014","journal-title":"Near Surf. Geophys."},{"key":"ref_25","doi-asserted-by":"crossref","first-page":"3947","DOI":"10.1109\/TGRS.2013.2278297","article-title":"Improved characterization of fine-texture soils using on-ground GPR full-waveform inversion","volume":"52","author":"Busch","year":"2014","journal-title":"IEEE Trans. Geosci. Remote Sens."},{"key":"ref_26","doi-asserted-by":"crossref","first-page":"128","DOI":"10.1016\/j.jappgeo.2016.01.019","article-title":"Experimental study of soil compaction effects on GPR signals","volume":"126","author":"Wang","year":"2016","journal-title":"J. Appl. Geophys."},{"key":"ref_27","doi-asserted-by":"crossref","first-page":"3131","DOI":"10.1002\/2013WR014583","article-title":"Joint estimation of soil moisture profile and hydraulic parameters by ground-penetrating radar data assimilation with maximum likelihood ensemble filter","volume":"50","author":"Tran","year":"2014","journal-title":"Water Resour. Res."},{"key":"ref_28","first-page":"53","article-title":"Integrating geophysical and geostatistical techniques to map the spatial variation of clay","volume":"171","author":"Castrignano","year":"2012","journal-title":"Geoderma"},{"key":"ref_29","doi-asserted-by":"crossref","first-page":"574","DOI":"10.1029\/WR016i003p00574","article-title":"Electromagnetic determination of soil water content: Measurements in coaxial transmission lines","volume":"16","author":"Topp","year":"1980","journal-title":"Water Resour. Res."},{"key":"ref_30","doi-asserted-by":"crossref","first-page":"269","DOI":"10.3997\/1873-0604.2015006","article-title":"Mapping the spatial variation of soil moisture at the large scale using GPR for pavement applications","volume":"13","author":"Benedetto","year":"2015","journal-title":"Near Surf. Geophys."},{"key":"ref_31","doi-asserted-by":"crossref","first-page":"48","DOI":"10.1016\/S0022-1694(01)00336-5","article-title":"Soil water content measurements at different scales: Accuracy of time domain reflectometry and ground penetrating radar","volume":"245","author":"Huisman","year":"2001","journal-title":"J. Hydrol."},{"key":"ref_32","doi-asserted-by":"crossref","unstructured":"Bradford, J.H., Harper, J.T., and Brown, J. (2009). Complex dielectric permittivity measurements from ground-penetrating radar data to estimate snow liquid water content in the pendular regime. Water Resour. Res., 45.","DOI":"10.1029\/2008WR007341"},{"key":"ref_33","doi-asserted-by":"crossref","first-page":"32","DOI":"10.1016\/S0022-1694(01)00588-1","article-title":"On the use of combined geophysical methods to assess water content and water conductivity of near-surface formations","volume":"259","author":"Garambois","year":"2002","journal-title":"J. Hydrol."},{"key":"ref_34","doi-asserted-by":"crossref","first-page":"77","DOI":"10.1016\/0926-9851(95)90031-4","article-title":"Analysis of GPR data: Wave propagation velocity determination","volume":"33","author":"Tillard","year":"1995","journal-title":"J. Appl. Geophys."},{"key":"ref_35","doi-asserted-by":"crossref","first-page":"178","DOI":"10.1109\/JSTARS.2015.2466174","article-title":"Analysis of GPR early-time signal features for the evaluation of soil permittivity through numerical and experimental surveys","volume":"9","author":"Comite","year":"2016","journal-title":"IEEE J. Sel. Top. Appl. Earth Obs. Remote Sens."},{"key":"ref_36","doi-asserted-by":"crossref","first-page":"11","DOI":"10.2136\/vzj2016.03.0026","article-title":"Early-time GPR: A method to monitor spatial variations in soil water content during irrigation in clay soils","volume":"15","author":"Algeo","year":"2016","journal-title":"Vadose Zone J."},{"key":"ref_37","doi-asserted-by":"crossref","first-page":"11","DOI":"10.2136\/vzj2018.01.0001","article-title":"A Comparison of Ground-Penetrating Radar Early-Time Signal Approaches for Mapping Changes in Shallow Soil Water Content","volume":"17","author":"Algeo","year":"2018","journal-title":"Vadose Zone J."},{"key":"ref_38","doi-asserted-by":"crossref","first-page":"175","DOI":"10.1016\/S0926-9851(99)00057-9","article-title":"Maximizing the information return from ground penetrating radar","volume":"43","author":"Olhoeft","year":"2000","journal-title":"J. Appl. Geophys."},{"key":"ref_39","doi-asserted-by":"crossref","first-page":"73","DOI":"10.1016\/S0926-9851(98)00017-2","article-title":"Electrical properties of water in clay and silty soils","volume":"40","author":"Saarenketo","year":"1998","journal-title":"J. Appl. Geophys."},{"key":"ref_40","doi-asserted-by":"crossref","first-page":"125","DOI":"10.4133\/JEEG1.B.125","article-title":"Transmission dispersion and GPR","volume":"1","author":"Annan","year":"1996","journal-title":"J. Environ. Eng. Geophys."},{"key":"ref_41","doi-asserted-by":"crossref","first-page":"81","DOI":"10.1016\/j.jappgeo.2013.05.003","article-title":"Frequency dependent electric properties of homogeneous multi-phase lossy media in the ground-penetrating radar frequency range","volume":"97","author":"Patriarca","year":"2013","journal-title":"J. Appl. Geophys."},{"key":"ref_42","doi-asserted-by":"crossref","first-page":"H1","DOI":"10.1190\/geo2012-0266.1","article-title":"Effects of magnetite on high-frequency ground-penetrating radar","volume":"78","author":"Hendrickx","year":"2013","journal-title":"Geophysics"},{"key":"ref_43","doi-asserted-by":"crossref","first-page":"11","DOI":"10.1046\/j.1365-2478.2004.00397.x","article-title":"Modelling of GPR waves for lossy media obeying a complex power law of frequency for dielectric permittivity","volume":"52","author":"Bano","year":"2004","journal-title":"Geophys. Prospect."},{"key":"ref_44","doi-asserted-by":"crossref","first-page":"1657","DOI":"10.1190\/1.1437549","article-title":"Modeling frequency-dependent GPR","volume":"16","author":"Powers","year":"1997","journal-title":"Lead. Edge"},{"key":"ref_45","doi-asserted-by":"crossref","first-page":"89","DOI":"10.1016\/j.jappgeo.2013.03.012","article-title":"GPR spectral analysis for clay content evaluation by the frequency shift method","volume":"97","author":"Benedetto","year":"2013","journal-title":"J. Appl. Geophys."},{"key":"ref_46","doi-asserted-by":"crossref","first-page":"J7","DOI":"10.1190\/1.2710183","article-title":"Frequency-dependent attenuation analysis of ground-penetrating radar data","volume":"72","author":"Bradford","year":"2007","journal-title":"Geophysics"},{"key":"ref_47","doi-asserted-by":"crossref","first-page":"1.1","DOI":"10.1029\/2001WR000923","article-title":"Radar frequency dielectric dispersion in sandstone: Implications for determination of moisture and clay content","volume":"39","author":"West","year":"2003","journal-title":"Water Resour. Res."},{"key":"ref_48","doi-asserted-by":"crossref","first-page":"15","DOI":"10.1002\/arp.396","article-title":"Comparison of a stepped-frequency continuous wave and a pulsed GPR system","volume":"18","author":"Leckebusch","year":"2011","journal-title":"Archaeol. Prospect."},{"key":"ref_49","doi-asserted-by":"crossref","first-page":"42","DOI":"10.1016\/j.jappgeo.2014.11.003","article-title":"Stepped-frequency radar signal processing","volume":"112","author":"Seyfried","year":"2015","journal-title":"J. Appl. Geophys."},{"key":"ref_50","doi-asserted-by":"crossref","unstructured":"Sala, J., Penne, H., and Eide, E. (2012, January 4\u20138). Time-frequency dependent filtering of step-frequency ground penetrating radar data. Proceedings of the 2012 14th International Conference on Ground Penetrating Radar (GPR), Shanghai, China.","DOI":"10.1109\/ICGPR.2012.6254904"},{"key":"ref_51","doi-asserted-by":"crossref","unstructured":"Eide, E., V\u00e5land, P.A., and Sala, J. (July, January 30). Ground-coupled antenna array for step-frequency GPR. Proceedings of the 2014 15th International Conference on Ground Penetrating Radar, Brussels, Belgium.","DOI":"10.1109\/ICGPR.2014.6970527"},{"key":"ref_52","doi-asserted-by":"crossref","first-page":"153","DOI":"10.1023\/A:1020399314530","article-title":"Image processing-based mine detection techniques: A review","volume":"3","author":"Paik","year":"2002","journal-title":"Subsurf. Sens. Technol. Appl."},{"key":"ref_53","doi-asserted-by":"crossref","first-page":"1136","DOI":"10.1093\/comjnl\/bxq066","article-title":"Image retrieval system based on adaptive color histogram and texture features","volume":"54","author":"Lin","year":"2010","journal-title":"Comput. J."},{"key":"ref_54","doi-asserted-by":"crossref","first-page":"892","DOI":"10.1049\/iet-rsn.2016.0491","article-title":"Dependence of landmine radar signature on aspect angle","volume":"11","author":"Lombardi","year":"2017","journal-title":"IET Radar Sonar Navig."},{"key":"ref_55","doi-asserted-by":"crossref","first-page":"107","DOI":"10.1016\/j.jappgeo.2013.04.010","article-title":"Ground penetrating radar (GPR) attribute analysis for archaeological prospection","volume":"97","author":"Zhao","year":"2013","journal-title":"J. Appl. Geophys."},{"key":"ref_56","doi-asserted-by":"crossref","first-page":"1072","DOI":"10.2136\/vzj2004.1072","article-title":"Electromagnetic inversion of GPR signals and subsequent hydrodynamic inversion to estimate effective vadose zone hydraulic properties","volume":"3","author":"Lambot","year":"2004","journal-title":"Vadose Zone J."},{"key":"ref_57","doi-asserted-by":"crossref","first-page":"73","DOI":"10.1007\/s11220-005-4228-x","article-title":"Frequency dependence of the soil electromagnetic properties derived from ground-penetrating radar signal inversion","volume":"6","author":"Lambot","year":"2005","journal-title":"Subsurf. Sens. Technol. Appl."},{"key":"ref_58","doi-asserted-by":"crossref","first-page":"69","DOI":"10.1016\/j.jappgeo.2013.04.006","article-title":"Clay content evaluation in soils through GPR signal processing","volume":"97","author":"Tosti","year":"2013","journal-title":"J. Appl. Geophys."},{"key":"ref_59","doi-asserted-by":"crossref","first-page":"26","DOI":"10.1016\/j.jappgeo.2010.03.001","article-title":"Water content evaluation in unsaturated soil using GPR signal analysis in the frequency domain","volume":"71","author":"Benedetto","year":"2010","journal-title":"J. Appl. Geophys."}],"container-title":["Remote Sensing"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/2072-4292\/11\/9\/1075\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,11]],"date-time":"2025-10-11T12:49:40Z","timestamp":1760186980000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/2072-4292\/11\/9\/1075"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2019,5,7]]},"references-count":59,"journal-issue":{"issue":"9","published-online":{"date-parts":[[2019,5]]}},"alternative-id":["rs11091075"],"URL":"https:\/\/doi.org\/10.3390\/rs11091075","relation":{},"ISSN":["2072-4292"],"issn-type":[{"value":"2072-4292","type":"electronic"}],"subject":[],"published":{"date-parts":[[2019,5,7]]}}}