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:: Relating L-band scatterometer data with soil moisture content and roughness. P. J. F. Swart

Document type:: Multivolume work

Structure type:: Chapter

183 Symposium on Remote Sensing for Resources Development and Environmental Management / Enschede / August 1986 Relating L-band scatterometer data with soil moisture content and roughness P.J.F.Swart Delft University of Technology, Netherlands ABSTRACT: Preliminary results are reported of the analysis of L-band airborne radar backscatter data from lar ge homogeneous agricultural fields. Examples are given of the calculated normalized radar cross section versus incidence angle. The main theme of discussion will be this angular dependency and its relation with measured soil moisture content and roughness. RESUME: Dans cet article-ci les résultats préliminaires de l'analyse du signal rétrodiffusé d'un scattérométre aéronautique functionnant àl.2GHz sont discutées. La région illuminée par le radar se compose des champs d'agriculture homogènes de plus que septante hectares. Le thème principal est l'influence de la rugosité et l'humidité du sol sur la dépendence du coefficient de rétrodiffusion en fonction de l'angle d'incidence. 1 INTRODUCTION Within the framework of the Shuttle Imaging Radar-B (SIR-B) experiment in October 1984 radar backscatter data were gathered with the airborne scatterometer DUTSCAT (Delft University of Technology Scatterometer) working in L-band (1.2 GHz). The test area with large sized agricultural fields lies in the southern part of the Flevopolders in The Netherlands. The flights with the scatterometer over these fields were perfor med by the National Aerospace Laboratory (NLR). The simultaneous collection of ground data was carried out by the Soil Survey Institute in cooperation with the Wageningen Agricultural University, both repre sented in the ROVE Working Group Soils. The objectives of the experiment were: 1. Calibration of the L-band radar on board of the Space Shuttle. 2. Testing the inverse use of a scatter model for bare soil. Due to a number of technical problems the Shuttle radar failed to produce data for our test area. Never theless scatterometer and ground data as well as flight parameters and video recordings were obtained. This meant that the intended modelling could still take place. In the following the theoretical aspects concerning the radar measurements will be described. After this the processing of the acquired scatterometer data is outlined. Some preliminary results of the angular de pendency of calculated normalized radar cross sections will be shown. Finally their relation with measured soil moisture content and roughness is discussed. 2 MEASUREMENT DESCRIPTION The DUTSCAT scatterometer is installed in the Beech- craft Queen Air research aircraft of the NLR. It is a well calibrated pulse type radar which is used for accurate measurements of land and sea. A scatterometer measures the power of scattered electromagnetic waves quantitatively. Although any amplitude-calibrated ra dar can be a scatterometer the most satisfactory mea surements are made with radars designed as scattero- meters. A technical description of the DUTSCAT system can be found in literature (Attema e.a. 1984). One of the most important properties of a scattero meter is that in order to improve radiometric accuracy a trade-off has been made against geometric resolution. To allow an explanation of how this applies to DUTSCAT we proceed with a synopsis of the underlying theory. 2.1 Theoretical aspects In a pulse radar spatial discrimination between sig nals received from different parts of the by the an tenna illuminated area is achieved by measuring time differences associated with different distances as seen from the radar. The resulting so called slant- range resolution is related to the time the radar needs to create a pulse, the pulse duration T. This relation is given by: Ar = cT/2 (1) with c the velocity of light (Krul 1986). We see in fig. 1 that the resolution distance on the ground perpendicular to flight direction follows as: Ay = cT/2sin0 (2) where 0 is the angle of incidence. For small incidence angles this across-track ground resolution becomes very large and ultimately the situation is reached where the resolution is determined by the half-power two way (or effective) antenna beamwidth in elevation. For the along-track direction the resolution can be approximated by the arc length corresponding to the azimuthal effective beamwidth 0^: Ax = B^R = B^h/cosB (3) It follows that the resolution in x-direction degrad es with increasing distance and/or incidence angle. Figure 1. Pulse-type radar geometry.

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