Remote Sensing Data Servers: An Enabling Technology for the development of Applications
Yves Henaaf, Jean-Francois Gallet, Gilles Richard, Michel Mariton
Matra Systemes & Information
6 Rue Dewoitine, 78142 Velizy-Villacoublay, France
1- Introduction
The early use of space-based earth observation was dominated by strategic concerns with limited operational applications, except for the notably successful use of spy satellite as a means to protect national interest. This period however allowed a maturation of the underlying technologies and a reduction of their cost.
The transition towards the development of applications with a larger user baadse is now feasible, and further facilitated by concurrent evolution on the general Information Technology scene (Windows NT, Java…).
This paper presents a key technological component, the Remote Sensing Data Server, from both technical and application points of view.
2-Application Needs
Satellite Remote Sensing data has proved that it can be extremely useful gathering many types of information, but is still strongly under utilized. Some experts have estimated that 85-90 Gigabytes of data produced has never been used for operational purposes.
Apart from limitations related to the earth observation space segment e.g. high investment and fixed cost, limited number of satellites and consequently low revisit cycles, there are technical obstacles to the wider use of Remote Sensing data associated with the ground segment (i.e. the chain of systems for data acquisition, transport, archiving, processing and delivery):
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Existing Earth Observation ground segments make only limited usse of on-line user access to data processing systems and advanced communication networks for interactive product retrieval.
- Earth Observation Products, e.g. satellite images, are mostly based on standardized geographical coverage's and may require substantial processing by the user. Many end users instead need smaller areas of derived information.
- Non-space data and in particular Geographical Information Systems data, important for many applications, are only starting to be integrated with satellite image data.
Improvement of the data supply chain and increase in the flexibility of data processing represents a major technological challenge for Ground Segment Information Systems.
3-Users'demand: Two Examples
3.1 - Impact Studies
Clean, non-polluting electricity habitat s better environmental credentials than many types of power, but its distribution is a live issue in more ways than one. In most Western countries, National distribution networks were established before the rise of the environmental lobby, but news high-voltage lines still have to be laid, ands old ones require renewal or relocation. Efforts are made to bury lower voltage electric lines, the caloric diffusion of high voltage lines is substantial, so these remain aerial for reasons of health and safety as much as cost.
Above all, electric power transportation must be secure, but planners must also be mindful of the visual impact of electricity lines. A typical problem is finding a way to increase energy transportation on an exiting line. Which is better - one large pylon or two small ones? How can we present a model which is comprehensive without being confusing? And most importantly, how can we justify the decisions we make?
In close cooperation with Electricity development France, the French National power utility, we analyzed the basic requirements for a system, called EVELINE, that integrates computer graphics technology with digital mapping, and can be used to model, simulate and view the impact of electricity lines of the environment.
Most projects will begin with an impact study, where a power supply company and local authority will assess the environmental implications of pylons and power lines. Determined by maps, orthophotos and other data, this will identify physical characteristics and other local constraints within which the project must operate. Each is given a weighting, and on this basis a decision made about the strip of terrain over which the supply line can be set up.
It is clear that Remote Sensing can contribute to the above problem, provided it is brought into the Impact Study domain by some enabling tools. Besides the electric power line example discussed above, similar requirements emerge for large freeway or dam projects, in fact any major construction project.
