Remote sensing for resources development and environmental management: Remote sensing for resources development and environmental management

Damen, M. C. J.

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Multivolume work

Persistent identifier:: 856342815

Title:: Remote sensing for resources development and environmental management

Sub title:: proceedings of the 7th international Symposium, Enschede, 25 - 29 August 1986

Year of publication:: 1986

Place of publication:: Rotterdam; Boston

Publisher of the original:: A. A. Balkema

Identifier (digital):: 856342815

Language:: English

Additional Notes:: Volume 1-3 erschienen von 1986-1988

Editor:: Damen, M. C. J.

Document type:: Multivolume work

Volume

Persistent identifier:: 856343064

Title:: Remote sensing for resources development and environmental management

Sub title:: proceedings of the 7th international Symposium, Enschede, 25 - 29 August 1986

Scope:: XV, 547 Seiten

Year of publication:: 1986

Place of publication:: Rotterdam; Boston

Publisher of the original:: A. A. Balkema

Identifier (digital):: 856343064

Illustration:: Illustrationen, Diagramme

Signature of the source:: ZS 312(26,7,1)

Language:: English

Usage licence:: Attribution 4.0 International (CC BY 4.0)

Editor:: Damen, M. C. J.

Publisher of the digital copy:: Technische Informationsbibliothek Hannover

Place of publication of the digital copy:: Hannover

Year of publication of the original:: 2016

Document type:: Volume

Collection:: Earth sciences

Chapter

Title:: 2 Microwave data. Chairman: N. Lannelongue, Liaison: L. Krul

Document type:: Multivolume work

Structure type:: Chapter

Chapter

Title:: Measurements of the backscatter and attenuation properties of forest stands at X-, C- and L-band. D. H. Hoekman

Document type:: Multivolume work

Structure type:: Chapter

Symposium on Remote Sensing for Resources Development and Environmental Management / Enschede / August 1986 121 Measurements of the backscatter and attenuation properties of forest stands at X-, C- and L-band D.H.Hoekman Wageningen Agricultural University, Netherlands ABSTRACT: The new airborne multi-band scatterometer (DUTSCAT) promises to be a useful tool for research in the field of active microwave remote sensing. An evaluation of the use of this system for research in forestry is given. Besides accurate o° values the system can acquire information on the vertical dis tribution of backscattering. Through inversion of the multi-level model the parameter a 0 can be divided • in contributions from a number of layers (3 or 4). An experiment with big corner reflectors placed on the forest floor was conducted in an effort to gain more insight into the attenuating properties of the forest canopy. The measurements of attenuation properties together with the division of O 0 in contributions from several layers simplifies the model-making effort considerably. KEYWORDS: Active microwave remote sensing, forest canopy attenuation, sources of scattering, modelling. I . INTRODUCTION The research activities of the working group ROVE- Forestry concentrate on modelling radar backscatte ring of forests and the identification of poten tial applications of radar remote sensing in fores try. Until recently experimenting in the Netherlands by ROVE-Forestry was limited to the use of an X-band, HH-polarized SLAR. The introduction of an airborne multi-band scatte rometer (DUTSCAT) in 1986 promises to be a major break-through in research possibilities. Some results in L- and C-band recently obtained with experi mental (single band) versions of the new system will be discussed in this paper. Both sensors (SLAR and scatterometer) are primarily used for the acquisition of accurate values of O 0 or Y • Other physical parameters like the canopy attenuation or the vertical distribution of sources of backscattering in the forest canopy can be mea sured too. The physical parameter Y is the only parameter SLR systems normally supply and this para meter together with the appropriate ground truth data would in principle suffice to study the poten tial applications of interest. Therefore it seems peculiar, at first sight, that the use of the re search instruments, the X-band SLAR and DUTSCAT, has not been limited to measurements of Y . The reason to measure other physical properties of the forest, as far as possible, is that these data can simplify the model-making effort considerably. Applying radar remote sensing in general asks for methods to interpret the acquired radar imagery. For some applications the spatial information (patterns, textures) is relevant, for other applications the temporal information (changes). For most applica tions however relevant information is contained in the absolute value of y .To extract this informa tion backscatter models are essential. The modelling can be done in various ways. For specific applica tions one can start from the assumption that rela tions between y values and object (forest) parame ters can follow empirically constructed expressions well enough. Modelling radar data on a physical basis however is more complicated but is to be pre ferred since these models are likely to have a broa der validity and can be used to extrapolate thus gained insights to other situations or to explain observed phenomena still unknown or unexpected. In general models with a physical basis describe the radar return y as a sum of direct contributions of different types of scatterers in the object's volume and interactions (e.g. multiple scattering) between these scatterers. In these models the inci dent power and the received backscattered power of scatterers in lower layers is attenuated by scat terers in layers, above. A direct acquisition of data on attenuation properties or a method to indicate the sources of scattering directly would be, along with Y measurements, of great importance in model research. 2. SENSOR DESCRIPTION .The X-band SLAR is internally calibrated and has digital recording facilities for radar and flight data. Pre-processing software has been developed to accurately correct the raw radar data both geometrically and radiometrically. The resulting imagery indicates relative Y values, the final pixel size is 7.5 meter square. The specifications of the SLAR are listed in table 1. Table 1. Specifications of Dutch digital SLAR. Frequency Antenna Transmitted power Pulse length PRF Polarization (Two-way) antenna beamwidth Sample frequency Dynamic range Pixel size Geometric resolution in range in azimuth Independent samples 9.4 GHz 2.5 m slotted wave guide 25 kW 50 ns 200 Hz HH 10 mrad 50 MHz (3 m) , 12 bits 70 dB 7.5 m x 7.5 m 7.5 m 10 m/km ~ 15 per pixel The airborne scatterometer DUTSCAT (Attema & Snoeij 1985) is sideways looking and of the coherent pulse type. The parabolic dish antenna has a two-way beam width of 13 degrees at L-band and 3 degrees at C-band, is mechanically steerable during flight and can be pointed between 0 degrees and 80 degrees incidence angle. The range resolution of 15 meters

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