Prent Status and Perspectives of Remote Sensing
of Vegetation
Juhan Ross
(T artu Ob r va tory,EE2444Tor a vere,T artu,Estonia)
During the recent decades a new discipline of biogeophysics remote nsing of vegetation has been born.T his w as stimulated by the need to describe in more detail the energy and m ass ex chang e betw een the g round surface and atmosphere in the mathemat-i cal models of the global and reg ional climate,by the need to have rapid inform ation about biological productiv ity and yield of the vegetation over the large areas and probably to most extent by m ilitary needs, connected w ith rocket piloting.The rapid develop-ment of remote nsing has bad on:
i)The existence of Earth s satellites,originally constructed for military and astronom ical needs.龟背竹
ii)The availability of the powerful enoug h com-puter technolog y for recording,data processing and analysis.
拥抱和接吻iii)The possibility to u the radiative transfer theory originally elaborated for astrophysics, atmospheric physics and neutron transport in nuclear reactors.
T he main problem of remote nsing of the veg e-tation might be formulated as follow s:measuring from satellites or airplanes electromagnetic radiation in optical,therm al and microw ave spectral regions reflected from vegetation and the solv ing the inversion problem to obtain information for classification, distribution,functioning and productiv ity of different kinds of vegetation over the w hole Earth surface. Reflected from veg etation electromag netic radiation is determined by the following factors:
骨龄偏大一定长不高吗i)Conditions of illumination above the veg eta-tion.
ii)The disturbing influence of the atmosphere in propagation of the reflected radiation.
iii)T he properties of the vegetation and soil in scattering of the radiation.
仙人掌的用处
iv)The architecture of the w hole canopy as w ell as individual plants.
There ex ist different fundamental and practical difficulties which limit the solving of the m ain prob-lem.
1)Within a certain type of vegetation the varia-tion of the reflected radiation is great within pix els variations m ay ex ceed variations between pix els.T he main reason of the variations is the miregular structure and inhomogeneity of vegetation itlf. The v ariations are sm aller for cultural vegetation and greater for natural one, e.g.for forests and shrubs.订快餐
2)Nonflat relief of the g round surface changing the conditions of illum ination.
3)The existence of the cloud cover in the Earth atmosphere drastically limiting the possible time for remote nsing in optical and thermal spectral reg ions.
4)Lack of detailed enough information about3D distribution of the optical properties of the atmosphere resulting in erroneous atmospheric correction.
5)Different technical errors,connected w ith nsor calibration and stability,w ith reg istration,da-ta processing,etc.
Due to the difficulties the inver problem having the measuring data of the reflected radiation about some certain type of vegetation to determine the optical and architectural parameters of this vegetation must be m athematically treated as incorrect inver
第1卷增刊1997年 5月
遥 感 学 报
JOURNAL OF REM OTE SENSING
V ol.1,Suppl.
M ay, 1997
葡萄是什么季节的problem.During further development of the remote nsing technology,theory and methodolog y the accuracy to solve the incorrect inver problem might be incread but the main lim iting factor remains obtained by remote nsing vegetation parameters quite poorly ex press the main biolog ical process photosynthesis,respiration,transpiration,alloca-tion,etc,of the g row ing vegetation.In the nearest future the perspective problems of vegetation remote nsing studies are probably the follow ing:
1.Further development of active methods by means of lidars and microwave radars.
2.Simultaneous measurements in optical,ther-mal and microw ave spectral regions.
最粗的树3.U of the angular distribution of reflected radiation and further development of the BDRF models in solving the inver problem.
什么是闪点
4.M ore detailed in optical region spectral analy-sis of the reflected radiation by means of CCD nsors.
5.Repeated during the vegetation period mea-surements of the same objects connected w ith phono-log ical models.
6.Development of the principles and methods for regional averaging of vegetation characteristics.
7.Using data of all spectral regions to develop new SPAM models for different types of vegetation.
8.Development of combined integ ral models for describing functioning,productivity and y ield of different types of vegetation using all data ts geo-graphical,ground rvice and remote nsing.
AUTHOR
Juhan Ross,born in1925in Estonia.Graduated from Tartu University,Physics Faculty in1951and obtained Ph.D.in1957 at Main Geophysical Obrvatory,Leningrad,D.Sc.in optical in 1978at Tartu Un
iversity.Professor of geophysics from1978, Academician of Russian Acad.Agric.Sci.from1988,1993 Doctor honoris causa at University Joensuu,Finland.Senior Re-arch Sci enti st at Tartu Obrvatory,his rearch fields are ra-diative transfer in plant canopy,remote nsing of vegetation, crop productivity models.Author of4monographs and about130 published papers.
植被遥感的现状与展望
Juhan Ross
(Tartu Obrvatory,EE2444Tor a vere,Tartu,Estonia)
2 JOURNAL OF REMOTE SENSING Vol.1
