Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Radar teledetection for estimating the superficial humidity of soil

03.02.2006
Photographic images captured by radar satellites enable the superficial humidity of agricultural basins to be estimated with great precision, although it is important to have knowledge of the rugosity of the surface.
This is the conclusion of Jesús Álvarez Mozos in his PhD thesis, Evaluation of the applicability of radar teledetection in estimating the superficial humidity of agricultural basins, defended recently at the Public University of Navarre.

Roughness of the terrain

Jesús Álvarez Mozos analysed photographs taken by two currently active radar satellites, RADARSAT-1 and ENVISAT/ASAR, that respectively belong to the Canadian Space Agency and the European Space Agency. In concrete, seven images were studied and which correspond to the Navarre Government experimental agricultural basin known as the Tejería, located near Villanueva de Yerri.

From this analysis, Álvarez Mozos has concluded that a good knowledge of surface rugosity is a key factor in order to make a correct estimate of humidity based on photographic images. Roughness is based on random variations of the terrain and depends on the crops grown and the tasks carried out on the soil. For example, a field on which a furrow plough has worked will be rougher than one that has been sown with seed. In other words, the high spatial variability of the field, on the one hand, and, the sensitivity of the coefficient of retrodispersion to its parameters, on the other, behoves a more detailed characterisation.

Given the importance of this parameter and with the aim of being able to measure it, a laser profilometer was designed. This proved to be a very valuable tool for the study of rugosity. Thus, based on measurements taken with this instrument, the behaviour of various existing parameters was analysed for rugosity, as well as the influence of tilling the soil on such parameters, its variability or scale of measurement which proved to be suitable in order to characterise the rugosity of agricultural surfaces in an optimum manner.

Reliablity of the scale of a geographical/agricultural basin

Once the rugosity data for a specific terrain was measured, estimates for humidity - on the scale of a geographical basin - were obtained from the high-reliability images. The reliability of the estimates improves with the level of aggregation or scale with which the humidity is estimated. In this research, geographical basin-scale estimates were obtained which had an error of 0.06 cm3cm-3, comparable to that obtained with humidity measurement methods in situ.

The results of the research pointed to the fact that another parameter that bears on the measurement of humidity through teledetection is vegetation. However, it is possible to correct the influence of this in quite a simple way. Thus, values or characteristic variables of wheat, for example, given that the zone analysed is a dry farming one (cereal crop and its biomass), may be corrected and representative values for the soil obtained.

Radar satellites

Knowledge of soil humidity can be of great utility in, for example, the detection of water stress conditions or to set out needs for crop irrigation, as well as to evaluate damage due to drought and to administer the concomitant remedial measures.

Over the last fifty years, with the aim of estimating soil humidity, a number of techniques have been developed which can be classed into two types: precise estimates and those based on teledetection. The latter enable the estimation of the humidity content of the surface based on the measurement of electromagnetic radiation emitted and/or reflected by it. In general, the measurement of this radiation is undertaken by means of electronic sensors installed on space platforms.

In concrete, the satellites studied for this thesis incorporate synthetic aperture radar sensors (SAR), which are being increasingly used for evaluating natural resources. Amongst its advantages, the fact that photographs can be taken whether there are clouds or not, is particularly important. Moreover, the main space agencies (Canadian, Japanese, etc.) plan to launch a number of satellites of this type in 2006 and 2007, all with enhanced characteristics with respect to those studied for this thesis.

Irati Kortabitarte | alfa
Further information:
http://www.basqueresearch.com/berria_irakurri.asp?Gelaxka=1_1&hizk=I&Berri_Kod=875

More articles from Agricultural and Forestry Science:

nachricht Plasma-zapping process could yield trans fat-free soybean oil product
02.12.2016 | Purdue University

nachricht New findings about the deformed wing virus, a major factor in honey bee colony mortality
11.11.2016 | Veterinärmedizinische Universität Wien

All articles from Agricultural and Forestry Science >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Significantly more productivity in USP lasers

In recent years, lasers with ultrashort pulses (USP) down to the femtosecond range have become established on an industrial scale. They could advance some applications with the much-lauded “cold ablation” – if that meant they would then achieve more throughput. A new generation of process engineering that will address this issue in particular will be discussed at the “4th UKP Workshop – Ultrafast Laser Technology” in April 2017.

Even back in the 1990s, scientists were comparing materials processing with nanosecond, picosecond and femtosesecond pulses. The result was surprising:...

Im Focus: Shape matters when light meets atom

Mapping the interaction of a single atom with a single photon may inform design of quantum devices

Have you ever wondered how you see the world? Vision is about photons of light, which are packets of energy, interacting with the atoms or molecules in what...

Im Focus: Novel silicon etching technique crafts 3-D gradient refractive index micro-optics

A multi-institutional research collaboration has created a novel approach for fabricating three-dimensional micro-optics through the shape-defined formation of porous silicon (PSi), with broad impacts in integrated optoelectronics, imaging, and photovoltaics.

Working with colleagues at Stanford and The Dow Chemical Company, researchers at the University of Illinois at Urbana-Champaign fabricated 3-D birefringent...

Im Focus: Quantum Particles Form Droplets

In experiments with magnetic atoms conducted at extremely low temperatures, scientists have demonstrated a unique phase of matter: The atoms form a new type of quantum liquid or quantum droplet state. These so called quantum droplets may preserve their form in absence of external confinement because of quantum effects. The joint team of experimental physicists from Innsbruck and theoretical physicists from Hannover report on their findings in the journal Physical Review X.

“Our Quantum droplets are in the gas phase but they still drop like a rock,” explains experimental physicist Francesca Ferlaino when talking about the...

Im Focus: MADMAX: Max Planck Institute for Physics takes up axion research

The Max Planck Institute for Physics (MPP) is opening up a new research field. A workshop from November 21 - 22, 2016 will mark the start of activities for an innovative axion experiment. Axions are still only purely hypothetical particles. Their detection could solve two fundamental problems in particle physics: What dark matter consists of and why it has not yet been possible to directly observe a CP violation for the strong interaction.

The “MADMAX” project is the MPP’s commitment to axion research. Axions are so far only a theoretical prediction and are difficult to detect: on the one hand,...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

ICTM Conference 2017: Production technology for turbomachine manufacturing of the future

16.11.2016 | Event News

Innovation Day Laser Technology – Laser Additive Manufacturing

01.11.2016 | Event News

#IC2S2: When Social Science meets Computer Science - GESIS will host the IC2S2 conference 2017

14.10.2016 | Event News

 
Latest News

Porous crystalline materials: TU Graz researcher shows method for controlled growth

07.12.2016 | Materials Sciences

Simple processing technique could cut cost of organic PV and wearable electronics

06.12.2016 | Materials Sciences

3-D printed kidney phantoms aid nuclear medicine dosing calibration

06.12.2016 | Medical Engineering

VideoLinks
B2B-VideoLinks
More VideoLinks >>>