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superior for delineation of geomorphological features and
surface water bodies of the ground scene, the imagery from
optical multispectral RS systems, when available, is superior
for discrimination of vegetation classes. For some areas in
humid tropics, outside the range of ground receiving stations,
it may take years before a good quality image is acquired by an
optical RS system. Regarding the environmental monitoring
applications, the SAR systems are prefered when monitoring
at frequent or fixed intervals is required, because of their all-
weather, day-and-night image recording capacity. They are
particularly suitable for monitoring the extent and assessing
the impact of natural and man-made disasters. Both systems
are complementary and the availability of RS data from both,
the optical as well as SAR systems is an essential requirement
for operational land cover mapping and environmental
monitoring applications.
One of the most important criteria for judgement of the
usefulness of land cover maps and environmental monitoring
products is the extent to which their information content
reflects the current situation. While the topographic databases
and maps have a relatively stable information content and
serve for as long as 10 - 20 years without the need for major
revision, the land cover maps have to be updated more
frequently. Their actual update intervals depend on the rate of
land cover change and this may differ from one map sheet to
another. For example, in areas subject to high rate of
development activities, deforestation, land degradation, etc.,
updating of land cover information at annual intervals may be
necessary. Forecasting and assessment of impacts of natural
disasters, such as floods, forest and grassland fires, requires
monitoring at frequent intervals. The EO satellites with SAR
and optical RS systems, linked with GPS and GIS,
international geospatial information networks, and electronic
data transfers, provide the technical and economical means for
practically continuous monitoring of changes in land cover all
over the world.
International standards for RS data and the derived products
(Section 2.9) used by the regional and global land cover
mapping and environmental monitoring programs will have an
increasingly important role in contributing to their closer
coordination and effective implementation. Such international
programs will typically require RS data from several EO
satellites, recorded and processed in different countries.
Furthermore, RS data will have to be integrated with other
geospatial data, such as topographic, as well as with ground
verification data supplied by participating countries. In order
to fulfill this role, the relevant standards for different types of
geospatial data and products, as well as for electronic data
transfers, will have to be harmonized and closely followed
during all the design and implementation phases of regional
and global mapping and monitoring programs. There is a
worldwide convergence of opinions on these issues and
Significant progress has already been made. It has been
helped by relatively coarse scales used by the regional and
global mapping and monitoring programs:
1:100 000 to 1 : 250 000 for regional applications;
1: 1 million to 1 : 5 million for global applications.
Geospatial information at these scales is usually available
Without restriction for use by the regional and global
programs.
419
4.2 Standardization of Land Information Databases
There are many common features between the ongoing and
planned regional and global land cover mapping and
monitoring programs. (Section 5). All these programs and,
more importantly, the end users of their products and services,
would benefit from their closer coordination and, when
appropriate, cooperation. While such coordination is an
obvious requirement for the programs belonging to each of
these two types of applications, the land cover mapping and
environmental monitoring respectively, it should be extended
across the application barrier and include both types of
programs. It would increase the efficiency of their
implementation and improve their results. The land cover
mapping programs would have a possibility of bringing up-
to-date their databases with results from environmental
monitoring programs, while these would benefit from access to
more accurate, reference, land cover mapping database.
Recent advances in geomatics technologies of satellite remote
sensing, global positioning systems and geographic
information systems are bringing the remote sensing
methodologies for land cover mapping and environmental
monitoring closer together. Sharing the same geospatial data,
when appropriate, will reduce the cost of their acquisition and
processing. It is therefore recommended that all the regional
and global land cover mapping and environmental monitoring
programs establish effective linkages between their respective
land information databases (LIDs). This requires development
of a comprehensive LID, compatible with both, the land cover
mapping and environmental monitoring applications. Another
requirement is to link the LIDs with dedicated information
networks, as well as with the public access Internet. It would
open their access not only to other regional and global
programs, but also to geospatial databases of several major
RS data producing countries and international organizations.
Furthermore, it would facilitate wider dissemination of timely
information on geospatial data and derived products generated
by the regional and global land cover mapping and
environmental monitoring programs and would lead to their
increased impacts and cost-benefits. It would also be easier to
reference the monitoring of changes in vegetation cover, bare
land, surface water bodies and land use to a corresponding
land cover map. Consequently, it would be possible to broaden
the number of mapping and monitoring products generated
from such comprehensive LIDs. These products would be
available in the form of land cover line maps; image maps;
change maps; and statistics. Another group of products,
needed for the assessment and forecasting activities, would
result from mathematical modeling. Examples of the former
include the assessment of deforestation or land degradation
rates, land suitability for cultivation of specific crops,
irrigation or aquaculture; etc. Examples of the latter include
the forecasting of agricultural crop production; agricultural
drought; floods; etc A system flowchart for the above concept
is in Fig. 1. It is based on the central, integrating role of GIS
feeding and, when new data are available, refreshing the
comprehensive LID.
Hence, each comprehensive LID would be kept up-to-date
through monitoring activities, and thus reflect continuous
environmental changes caused by increasing population
pressures, climate vagaries and natural disasters. Close links
between the regional and global land cover mapping and
International Archives of Photogrammetry and Remote Sensing. Vol. XXXI, Part B4. Vienna 1996
