# EARTH OBSERVATION

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| The very nature of satellite-based Earth observation makes it a source of a special kind of information concerning our planet and hence our environment. Again by its very nature, this information covers a range of areas including topographic and thematic mapping, agriculture, forestry, geology, urban and rural management, the impact of major development projects, and more. All fields in which SPOT data find potential applications.

The major trends of the market for satellite-based Earth observation data are summarized below.

Mapping applications, in the broadest sense, are increasingly important. The combination of excellent spatial resolution and high geometric quality make SPOT imagery useful for mapping at standard scales from 1:100 000 to 1:25 000, particularly when maps are required for national economic development. According to UN statistics, only 44 % of the Earth's major land masses have been mapped at these scales, and many of these are obsolete, unreliable or inaccurate.

A SPOTView imagemap is a mosaic of SPOT imagery geometrically corrected to a given projection and matching local mapsheets. These standard products register perfectly with existing maps, are easy to read, and present the user with current information, in the form of imagery of actual ground cover. A large number of projects using GeoSPOT are currently in progress. In Bangladesh, for instance, GeoSPOT coverage at 1:50 000 is used as a geographical base flood monitoring.

The relevance of SPOT data to mapping work at intermediate scales is demonstrated by the many intense efforts to make satellite data easier to use with geographic information systems (GISs). A GIS combines data from a variety of sources, matching them to a common reference base, so that different types of information can be cross-correlated, sometimes in highly sophisticated ways. After appropriate processing, SPOT data are ideal since they can be loaded directly in digital form into a GIS, supplying information that is both exhaustive and up-to-date. GISs are used as decision-making aids by a growing range of organizations with responsibilities in land and resource management. With a growth rate of over 30% per year, the GIS market is expanding very rapidly indeed. The natural synergy between SPOT data and the world of GIS opens some extremely promising prospects.

The Commission of the European Communities uses satellite data as a basic tool for inventorying biophysical land cover at 1:100 000 over all EC member states. The aim of the Corine programme is to set up an environmental database covering the entire EC.

SPOT's stereo capability combined with its excellent revisit flexibility make it ideal for studying earthflows, including land, rock and mudslides and for example, compiling earthflow hazard maps taking into account terrain, geological, tectonic, morphologic and other parameters.

SPOT's unique stereo capability also means that SPOT stereopairs can be used to produce digital elevation models with excellent elevation and planimetric accuracy. Such DEMs are well suited to a range of applications in monitoring, military surveillance, and telecommunications. Examples include:

- 3-D display of terrain relief,
- plotting and display and low-level approach routes,
- animated imagery for the simulation and study of very-low-level flight paths,
- radiowave propagation models,
- line-of-sight (LOS) visibility maps.

In agriculture, SPOT data are now increasingly viewed as an integral component of major development projects. For its common agricultural policy, the European Community needs to identify and estimate the areas sown to major crops, and particularly those receiving subsidies based on the area cultivated. Good market management demands forecasts that are reliable, consistent in quality, and quickly available. High-resolution satellite imagery has demonstrated its usefulness for estimating crop areas and is now an integral part to the EC's operational agricultural statistics system set up as part of the Mars project (Action IV).

Several countries engaged in major land reform projects are compiling rural cadastral maps based on SPOT data, particularly for mapping agricultural land parcels.

Geographic information is also of interest to statisticians who are increasingly aware to the contribution satellite data can make to official statistics. Eurostat is considering improvements to the European Statistical Information System in which satellite-based earth observation data would provide the geographic reference. This type of application is enjoying strong growth. Specialists are already using SPOT imagery covering vast tracts of land to prepare large-scale surveys and censuses.

These brief descriptions of selected applications gives an indication of the many uses to which SPOT data can be put.