Nadir looking airborne radar and possible applications to forestry

Bernard, R.; Frezal, M. E.; Madjar-Vidal, D.; Guyon, Dominique; Riom, J.

doi:10.1016/0034-4257(87)90014-9

Cited by 32 publications

(6 citation statements)

References 5 publications

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“…In the past, high range resolution airborne scatterometer providing vertical backscatter profiles have been used to study the interaction of the microwaves in the canopy, using the experimental approach [11] or the semi-theoretical approach with the simple water cloud model [12].…”

Section: Introductionmentioning

confidence: 99%

Measurements and modeling of vertical backscatter distribution in forest canopy

Martinez

Floury

Toan

et al. 2000

IEEE Trans. Geosci. Remote Sensing

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This paper presents the results of analysis and modeling of the airborne ranging Helsinki University of Technology Scatterometer (HUTSCAT) data obtained over an Austrian pine forest in southern France. The objective is to use high vertical resolution backscatter profiles to validate a model that is subsequently used to determine the scattering sources within a canopy and to understand the wave/tree interaction mechanisms.The backscatter coefficients derived from HUTSCAT measurements at X-band at near-normal incidence and polarizations HH, VV, and VH are analyzed. The tree crown backscatter separated from the ground backscattering shows a sensitivity of about 3 dB between 0 and 200 m 3 /ha.The estimation of tree height using HUTSCAT profiles gives very good results, with a mean precision of 1 m.The vertical backscatter profiles are compared with the output from the MIT/CESBIO radiative transfer (RT) model coupled with a tree growth architectural model, AMAP, which recreates tree architecture using botanical bases. An a posteriori modification to the RT model is introduced, taking into account the vertical and horizontal variability of the scattering area in order to correctly estimate the backscatter attenuation. The results show good agreement between both simulated and HUTSCAT-derived vertical backscatter distribution within the canopy.The penetration depth at near normal incidence is studied. Both simulated and experimental penetration depth are compared and appear to be of several meters, varying with the stand's age.Index Terms-Forest parameters retrieval, forest radar backscatter, radiative transfer modeling, ranging scatterometer.

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Section: Introductionmentioning

confidence: 99%

Measurements and modeling of vertical backscatter distribution in forest canopy

Martinez

Floury

Toan

et al. 2000

IEEE Trans. Geosci. Remote Sensing

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“…For instance, Bemard et al [14] have estimated an average lineal attenuation of 0.8 dB/m (radar frequency of 5.35 GHz), and, as at grazing angles the ray path lies close to the horizontal, it is likely that even for a 100 m-long forest and at higher frequency the wave is attenuated by several tens of dB.…”

Section: ) Influence Of the Forestsmentioning

confidence: 98%

Surface reflection at low-angle propagation

Rana

Webster

Magne³

1995

IEEE Trans. Antennas Propagat.

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A new derivation of the ground-reflection coefficient based on rough-surface scattering theory is proposed to predict surface mechanism effects on both overwater and overland microwave line-of-sight links. A detailed model of diffused scattering is constructed which agrees in part with available experimental data and monostatic radar measurements. The model allows one to take into account the effects of antenna directivity, refraction by superrefractive layers, and various types of vegetation cover.Using this model, it is shown that atmospheric and surface mechanisms cannot be dissociated in estimating the ground refection coefficient and that, on terrestrial links, it is necessary to introduce any forests as part of the terrain profile to estimate as accurately as possible the specular and the scattering reflection coefficients.

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“…C'est pourquoi, pour parer à ces limitations, l'utilisation de capteurs radar fournissant également des sondages verticaux du couvert, mais fonctionnant dans le domaine des microondes, a été proposée (Bernard et al 1987;. Le signal émis présente en effet l'avantage de pé-nétrer beaucoup plus profondément dans le couvert qu'un rayon optique et, de plus, il est insensible aux perturbations atmosphériques, permettant de travailler quelles que soient les conditions météorologiques et d'ensoleillemen,t puisque l'appareil emporte sa propre source de rayonnement (télédé-tection active).…”

Section: Introductionunclassified

Estimation de la hauteur des peuplements forestiers par diffusiomètre radar

Martinez¹,

Beaudoin²,

Durand³

et al. 2000

Can. J. For. Res.

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Cet article présente les résultats de l'analyse des données acquises par un diffusiomètre radar héliporté audessus de plantations de pin noir d'Autriche (Pinus nigra Arnold ssp. nigricans Host.) en Lozère, France. Cet appareil permet d'estimer la hauteur des arbres en fournissant des sondages verticaux du couvert. L'objectif de cet article est d'étudier la validité de ces mesures, puis d'analyser l'intérêt de ce type de capteurs pour une meilleure gestion du milieu forestier. L'analyse des mesures effectuées montre de très bon résultats concernant l'estimation des hauteurs moyenne et dominante, avec une erreur relative de 6%. Par des mesures du coefficient de rétrodiffusion radar, sont possibles également des estimations d'autres paramètres comme le volume de bois ou la surface terrière. Il est montré que le coefficient de rétrodiffusion radar est sensible à la biomasse dans la gamme de valeurs faibles à intermédiaires (0-200 m 3 /ha), d'autant plus lorsque le signal provenant du houppier est isolé du sol. L'estimation d'un paramètre comme le volume de bois sur pied à partir de régressions utilisant à la fois les mesures de hauteurs d'arbres et du coefficient de rétrodiffusion offre des résultats satisfaisants. Finalement, l'intérêt de ce type de système pour une gestion fine du milieu est discuté et un exemple d'application concernant l'estimation de la variabilité de l'indice de fertilité à l'intérieur d'une parcelle est présenté.Abstract: This paper presents the results of an analysis of radar airborne scatterometer data obtained over an Austrian black pine (Pinus nigra Arnold ssp. nigricans Host.) forest in Lozère, France. This system provides vertical sounding inside canopy from which can be derived tree height estimations. The objective of this paper is to analyse the validity of these measurements and, then, to study the interest of this kind of sensors for better forest management. The mean and top height estimations give very good results with a relative error of about 6%. The radar measures the backscatter coefficient of the vegetation from which can be estimated other parameters such as stem volume or basal area. The radar backscatter coefficient is found to be sensitive to the biomass in a low to intermediate range of values (0-200 m 3 /ha), particularly when the canopy backscattering is separated from the ground echo. The estimation of stem volume using a regression with both tree height estimations and backscatter measurements gives satisfying results. Finally, we discuss the interest of this kind of sensor data for an improved and detailed forest management giving an example of application on the evaluation of the variability of the local site index within a stand. Martinez et al. 1991

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Nadir looking airborne radar and possible applications to forestry

Cited by 32 publications

References 5 publications

Measurements and modeling of vertical backscatter distribution in forest canopy

Measurements and modeling of vertical backscatter distribution in forest canopy

Surface reflection at low-angle propagation

Estimation de la hauteur des peuplements forestiers par diffusiomètre radar

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