Christian Mahe

Pro-SIGEA(1): A GIS to visualise Interactions between the Power Transmission Network and the Environment in the Aquitaine Region

At the end of 1993, some years after the EDF's decision to take account of the environmental concern, Energie Aquitaine (an EDF Generation and Transmission division) decided to build Pro-SIGEA, a dedicated GIS to deal with its region's environmental data. It would be able to show interferences from the power transmission network on maps and to form these interferences into a hierarchy. In addition, the system might improve communication between different organisations dealing with long term planning problems.

To achieve the goals, ArcView with Access was chosen as the main query tool. Now technical EDF staff use Pro-SIGEA for various purposes within their areas.

Today, we should point out that :

- such a system is strongly dependent on the data input into the computer,

- though it is not difficult to form a hierarchy of classifications based on juridical aspects, it is not the same for the landscaped and ecological criteria. (Partly as a consequence of the earlier remark on input data.)

So, the main conclusion is that the task of modelling interferences between the environment and human activities is difficult precisely because they interact together in space and time;

Let us think that, for the power transmission network, Pro-SIGEA can be considered as a first step towards that goal.


During the sixties, France needed electricity everywhere. There was no discussion as to the best way to transmit electricity from one point to another. Decisions were being based on economical considerations; the straight line was quite often the best one.

At the end of the 1970s, when the Very High Voltage (in French Tres Haute Tension) network was being reinforced, the context changed : the global needs had been satisfied and ecological consciousness (following the events of May '68 and other demonstrations like Woodstock) was rising. It was at that time that EDF began to take account of this concern for the environment : in 1982 it signed an agreement with state authorities to show its good will.

In 1990 its strategic plan included environmental measures. EDF also concluded an agreement with the authorities to take steps to integrate the transmission network components into their surroundings. Later, EDF asked its regional divisions to plan the enhancement of the regional network considering the environmental constraints.

Inside the company, it has therefore become a necessity to develop knowledge and skills, as well as tools to achieve this apparently simple goal of visualising the transmission network together with identified sensitive areas or sites on maps. At the end of 1993, 'Energie Aquitaine', a regional division of EDF Generation and Transmission, decided to conduct a global project to deal with its region's environmental data. At the beginning it seemed that this project should be based on a strong partnership with the local DIREN (DIrections Régionales de l'ENvironnement), the state agencies in charge of environmental questions.

The challenge was clear : to collect the relevant data and make them available for easy consultation as well as producing layouts and cartographic output. Eventually it would be possible to relate them to external data. This was for two levels of use : internally for EDF staff doing studies on the network; externally to allow consultation by authorised third-parties dealing with long term planning problems, for instance local state agencies.

Also, it was thought that the tool and the associated database might improve communication between different parties who were not necessary used to communicating.

We propose to overview the different process stages without going too deeply into details but just stressing their main characteristics.


After an initial analysis, considering the challenge and the quantity of data to be handled and having sought advice from the centralised section in charge of automated cartography, Energie Aquitaine chose to build a dedicated GIS and named it SIGEA(2). It would be able, not only to show interferences between the transmission network and the environment, but also to form the interferences into a hierarchy.

As usual, however, it was necessary to specify the system.

The environmental constraints :

Firstly, Energie Aquitaine listed the classifications representing environmental constraints. These classifications correspond to legal obligations or regulations that people in charge of building and managing an electrical network must comply with. There can also be interesting classifications considering specific sites. These classifications are grouped into the following 5 classes :

- Natural landscapes and built up zones:

Historical buildings and their surroundings,


Safeguarded (urban) Areas,

Architectural, Urban and Landscaped Protected Zones (abbreviated in French ZPAUP)

These classifications aim at protecting a place against an alteration or a change in its visual aspect.

- Forests :

Various kinds of forests : those used to stabilise soils, those under control of the National Parks Service.

- Protected Natural Sites :

Decree on biotope,

Preservation of the shore line,

Law concerning the shore line,

Law concerning the mountains,



For these cases, what is contained inside the sites is more important that their visual aspect.

- Quality of Natural Protected Sites :

ZNIEFF : this label defines Natural Zones with an identified Interest for Ecology, plants (Flowers) or Wildlife.

ZICO : this label defines Zones presenting Interest for the Conservation of Birds.

- Birds :

This class takes into account elements involving birds in the proximity of the electrical network. For example migration routes crossing wires, nesting periods etc...

Origin of the information :

The body responsible for the generation or collection of the various types of information attached to each classification have been identified with the help of the DIREN whose one mission is to compile environmental data. It should also be mentioned that many DIREN use ArcInfo(3) to manage geocoded data.

Existing databases of the transmission network and existing GIS :

Within EDF the Cartography Section, a centralised unit of EDF Generation and Transmission Division, was using ArcInfo to maintain geographical databases of the Electrical Transmission Network at 3 scales : 1:1,000,000, 1:250,000 and 1:25,000. These produce various maps at a national level but the data are also available for EDF's local Units to produce output on their territory extent. In addition the Cartography Section have been studying software, such as ArcView(4), as query tools for geocoded data.

Consequently, major choices were made early:

Map scales :

A specialised company was asked to help with modelling and implementation, ANTEA a BRGM subsidiary (Mining and Geological Research Bureau) was chosen. A research student at Bordeaux University was selected to work on the project. The Cartography Section should be consulted for controls and had to supply the transmission network geo-database.


In addition to the points mentioned in the previous paragraph , SIGEA functionality had to allow :

Layouts and output should be overlaid on existing raster maps at 1:100:000 scale.

To form a hierarchy between interferences three criteria would be used :

The tool had also to be easy to use through a user-friendly interface and should comply with standards of cartography.


Database modelling.

Firstly, logical modelling rules of themes were established. For example : 'at 1:25,000 scale, historical buildings are considered as points'. Or, 'a forest can cover several municipalities'. Then each modelled object was matched with an ArcInfo object. Is it necessary to underline at this point that the use of a topological model such as the one available with ArcInfo is helpful in implementing spatial relationships? When each classification (corresponding to an ArcInfo coverage or an ArcView theme) was in a geocoded numerical form (if necessary after digitising) ANTEA entered the attached information following entity/relation diagrams.

System design.

The central idea on which the system is based is : ' to search on a spatial unit if an intersection or proximity between the transmission network and environmental themes exist. Then, depending on the strength of the interaction, each spatial unit can be indexed.' The municipalities' boundaries ('communes' in French) have been chosen as the smallest common spatial unit. So, attribute tables can be related via a single municipality's identifier (INSEE code). Using this mechanism, it was therefore possible to relate different views in a project.

Obviously some specific ArcView functionalities were used :

The right system has not come easily. After some failures, several improvements corresponding to several versions have been necessary to make an operational and easy to use version. For instance :


Today the system is used by EDF staff for various purposes. For example, consider a maintenance action is required on the network. Pro-SIGEA can quickly produce a map of sensitive birds areas showing nesting periods so that EDF can choose the best time to schedule the operation and inform the local associations for the protection of birds.

Another use of Pro-SIGEA is when planning the building of a new line. The system allows interactions to be sorted and the level of interferences to be appreciated. It also allows the legal aspect of interferences to be determined before the building project's mandatory impact study is published. For example Pro-SIGEA was able to tell EDF's technicians that the projected line between 'Le Marquis' and 'Le Blayais' might actually touch the donjon of Mareuil's castel. Though SIGEA does not replace the usual studies, it is helpful to have early knowledge of environmental aspects of a project.

Among other results obtained with Pro-SIGEA we should mention a map giving the weight of various interferences between the transmission network and the environmental data, considering the legal criterion at the municipality zoning. This weight has been classified in five classes and is based on an indicator measuring the severity of interferences. In the case of the legal criterion 3 values have been defined to form the hierarchy:

Then a value has been given to each constraint (or theme) pertaining to the legal criterion, so the system is able to compute the sum of all the constraints for each municipality.


The database and ArcView based tool that form Pro-SIGEA, the EDF version of SIGEA, are useful. Energie Aquitaine uses it as an aid in the decision making process in its technical field.

The environmental database and its use through SIGEA is now the responsibility of Aquitaine DIREN. An agreement has been concluded between EDF and Aquitaine DIREN to protect it and its use by third-party members. SIGEA which allows the exchange of data between EDF and DIREN facilitates communication between these two entities.

However several remarks should be pointed out :

Last but not least, Magali Barrue, the student who has worked on this tool, has shown that it is difficult to give a definitive definition of the term 'Environment'. More difficult is the task of modelling interferences between the environment and human activities even if, for the power transmission network, Pro-SIGEA can be considered as a first approach.

Notes :

(1) Pro-SIGEA is a registered mark of EDF.

(2) SIGEA became the name of the DIREN version which is now in charge of the environmental database.

(3) ArcInfo is a registered mark of Esri.

(4) ArcView is a registered mark of Esri.

(5) Access is a registered mark of Microsoft Corp.

Acknowledgements :

Thanks to Energie Aquitaine to have given me permission to present a paper about Pro-SIGEA.

Many thanks to Magali Barrue whose research report has been very helpful.

Special thanks to (native) English speakers who kindly corrected this text.

References :

Magali Barrué : 'Design and use of a tool aimed to classify and form hierarchy of interferences between planning project and the environment' - Research Memory for 'DEA' obtention - Université de Bordeaux III - 1995.

Serge Lombard : 'Cartography of the environment, Constraints Specifications' - EDF/Energie Aquitaine - ref : D.5580/LBDS/LLEM 2/12/1993 -

Isabelle Laurent : 'Definition and Production of Aquitaine Region environmental maps, Planning' - EDF/OSSE/Cartography Section - Ref : D4002-88/95023/STA/Indice 1 - 30/06/1995.

Christian Mahe
Cartography Section Head
EDF Generation and Transmission Division,
Transmission Design and Construction Department.
Immeuble Ampere - La Defense 6 - 34-40, Rue Henri Regnault.
92 400 Courbevoie - France.

Telephone: (33-1) 41 02 27 93
Fax: (33-1) 41 02 27 57