TheImprovement ofTropical and Subtropical Rangelands

REGIONAL RESOUROE ASSESSMENT 95
The United States has maintained an "open skies" policy in the
acquisition and distribution ofdatafrom the Landsat satellites. Since
the initiation of the Landsat program, ground-receiving stations have
been established in a number of countries around the world (see list
below). Images from these stations are available at a modest cost
and cover most parts of the earth (see table 4-1).
Where large areas are studied and extensive ground sampling
poses a problem, large-scale aerial photography may be required to
supplement satellite data and conventional aerial photography. This
is particularly true when the efficient multistage sampling approach
is employed. Nonconventional systems have been developed (see
figures 4-3a and 4-3b) that provide excellent data at low cost for
large areas (International Livestock Centre for Mrica, 1981). Where
budget presents no problem, conventional aerial photography can be
purchased from a service.
The variety of remote sensing systems currently. available ensures
that basic information on land resources can be produced
quickly at reasonable cost for almost any country. Should training
or re-training be necessary to benefit from these systems, practical
training courses are available at most mrJor agricultural universities,
and at many remote-sensing centers. Aside from short-term courses
(leM than one month duration), university training is generally part
of a longer-term advanced-degree program. However, a variety of
variable-duration, comprehensive training programs in all aspects
of remote sensing are available under Unesco auspices through the
International Institute for Aerial Survey and Earth Sciences (ITe),
350 Boulevard 1945, P.O. Box 6, AA Enschede, The Netherlands.
REfERENCES
In'-rnational Livestock Centre for Africa (ILeA). 1981. Lo.levcl Aerial SurwV
TceJaniquu. ILeA Monograph 4. International Livestock Centre for Africa,
Addis Ababa, Ethiopia.
McLeod, R. G. and H. B. Johnson. 1981. Resource inventory techniques uud
in the Calfornia desert conservation area. In Arid LtJruU Re,oun:c InwntOrilll:
Dewloping Oon-Efficient MctItoclI. General Technical Report WD-28:260-271.
U.S. Department of Agriculture, Foreat Service, Washington, D.C., USA.
Michell, C. W. and J. A. Howard. 1979. Lon4 S,Iltem atJNification. A Oue
HWto"l: Jordan. Food and Agriculture Organisation of the United Nations,
Rome, Italy.
TOW1l8hend, J. R. G., ed. 1981. Temain Anal,., aratl Remote Servirag. George
Allen and Unwin, London, England.