Genius Geomatics

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Geomod blog, Land

MithraSIG: How to simplify the creation of terrain from grids


The French Geographic Institute (IGN) and more and more data providers are delivering the ground in the form of ASC grids with small pixel size (1 m or even 10 cm).

MithraSIG creates a ground as points and contour lines. The integration function converts grids (“ASC” format for example) into points. The major problem lies in the fact that the number of points produced is huge (several millions) and not very relevant in the zones of almost flat landscape where the ground has no effect on the acoustic propagation (outside the ground effect).


Example: we have four ASC grids of 1000 x 1000 pixels with a pixel size of 1 m, that corresponds to four million points on 4 km².

Operating principle

The new MithraSIG function reduces the number of points from these grids by considering a maximum tolerated difference chosen by the user between the initial and produced data.

An altitude comparison is done for each point between a complete data triangulation and an approximate triangulation while remaining within the tolerance. The result thus obtained represents the feature points of the ground: ridges, peaks, valleys, slope breaks, and mounds. These are the points that we seek to identify and to model in acoustics.

Ground selection



Figure 1 Ground creation with a tolerance of 20 cm


Consequence on the ground

Consequnce on the ground

A tolerance of 20 cm divide the number of points by 250. The average deviation (with the original data) is 10 cm.

With a tolerance of 1 m, there is an average loss of precision of 50 cm and a theoretical maximum loss of 1 m. We reduce the number of points by more than 2600.

Consequence on simulation

Consequence on simulation

Comparisons are made with all the same calculation parameters. The average difference is made in absolute value in order to avoid that errors compensate each other.

The differences of calculation with and without simplification of the ground are weak. However, locally, one can find important differences: some rays appear as diffracted in one case and not on the other. This is especially true in the NMPB08 method where the height of the source is low (5 cm).




Simplification of the terrain depends on the wanted precision of the simulations: this precision varies between a city cartography and an environmental impact study.

We calculate from ray tracing: details below the wavelength (less than 10 cm) do not improve the precision of the simulations. We advise to always simplify the data (with a tolerance of 10 or 20 cm) which significantly reduces the number of points and computation time without altering the results.



Geomod blog, Land

Open Data and GIS software

What is Open Data? In few words, Open Data is “data that can be freely accessed, modified and shared by anyone”. Data can come from various public or private sources: governments, local authorities, communities, companies, NGO, etc.

Many websites like give a more detailed definition.

The licences

Open Data Licences

A licence defines which rights are given when using the data. In a nutshell, what we have the right to do with it. There are several types of licences for the Open Data. And even if they all aim to facilitate access and redistribution, they can differ from each other by the rights given. We can mention the best known as

Creative Commons (CC) which is more intended for creative content, Open Data Commons Public Domain Dedication and Licence (PDDL) and Open Data Commons Open Database License (ODbL) dedicated to databases.

Governments providing data can create their own licences. For example, the United Kingdom has the Open Government Licence (OGL), Germany with DL-DE licences and even Europe with the EUPL licence. A list of these licences can be found on the website

France has created its own licence « licence ouverte » (LO) based on the project Etalab that many cities have adopted. With this licence, it is possible to reproduce, modify, redistribute and use for commercial purposes provided that the source of the data and the date of the last update are mentioned.

Each licence has its own “rules” in terms of use and redistribution. It is therefore important for the user to learn about the licence associated with the data he is using. These licences are mostly available and promoted on Open Data platforms.

Source and content

Open data is present in many areas: culture, education, transports, science, environment, economics, mapping and many others. Moreover, the Big Data increases the amount of data and their types. This make it possible to find many types of data: statistics, reports, images, geometries, etc. All the data can be useful because even if a type may not be relevant alone, combined to another type of data, the value of the result can be very important. That is the strength of Open Data.

For GIS (Geographic Information System) and mapping software fields, the data is provided mostly by public entities. The French government makes the data available through its platform from the project Etalab. Today, more and more regions, conurbation or cities are making data available through their own platform.

This data can contain the ground (LIDAR survey, DTM, contour lines), 2D or 3D buildings, roads and railways, vegetation or water areas, backdrops, and others. This data is a rich and valuable resource to build its digital models that can be used in modelling software.

Open data formats in mapping software

To ensure the best compatibility between all users, the data is mostly in formats allowing to import and export in many software. For that purpose, there are files or web services.

In the mapping field, the formats that we find most often for Open Data are:

  • CSV format that can be used as “table join” in a GIS software.
  • KML, GeoJSON, SHP formats that can be used for vector data.
  • GeoTIFF and ASC formats for raster or meshing data.

Other formats exist but are less common today like GML or CityGML for 3D data, XML or GPKG. However, this is changing and they may become standards in the future.

Nevertheless, this is not always interesting to download the data as files for various reasons: the file can be too large, the data is too frequently updated, the amount of data to be displayed is too high, etc. In these cases, a web service or an API is a better solution to have access to the data.

In web service, there are the Web Map Service (WMS) or Web Feature Service (WFS), both standards of the OGC. These services provide georeferenced images for WMS or georeferenced geographic data for WFS.

Where to find Open Data?

Today, we can easily find Open Data on the internet. In recent years, it is a wish to share data for information, knowledge and transparency purposes.

The French government has its own platforms or You can find cadastral data, statistics on energy or population, roads axis, landmarks, etc.

The cities of France also have their own service providing data directly about the city, the districts, the population, etc. This is the case for Paris, Lyon, Strasbourg for example.

Regions have also their platform such as Grand Paris, PIGMA for Nouvelle-Aquitaine, or the region Provence Alpes Côte d’Azur.

Another major website for France is OpenData France which is an association aiming at “regrouping and supporting local authorities engaged in a process of opening public data and promoting all the process taken by these local authorities, in the purpose of the promotion of Open Data”. It includes the list of members of this association and in particular the local authorities with the link to their Open Data platforms.

There are also essential services like Open Street Map, which relies on a community of people from all fields to expand the project. It is worth noting that most of the important contributors are the governments themselves.

And other cities in the world also have their program for Open Data such as Geneva, Brussels, New York, or Europe and United-States.

Obviously, it is difficult to navigate among all the possibilities to obtain data. Fortunately, there are websites that include all the portals available in the world. This is the case of OpenDataSoft where you can browse a map of the world and find a portal.


Geomod Water Modelling InfoWorks ICM
Geomod blog, Water model

Which type of database to use in InfoWorks ICM: Standalone or Workgroup?

Some InfoWorks ICM users often see error messages when they try to open their database (DB) or a network. These likely are signs of database corruption. The database restauration is difficult, time consuming and sometimes impossible. Then, this article will review the conditions to use the 2 available types of database in InfoWorks ICM in order to limit the database corruption and the loss of time. The two available database types are:

  • The Standalone database
  • The Workgroup database

The Standalone DB is represented by an .icmm file whereas the Workgroup DB is represented by a .sndb folder. It is important to note these two types of DB are totally independent from the type of licence (floating or standalone). These two types of DB are available whatever type of licence is used. For the users who might already use the wrong type of DB, taking huge risk of DB corruption, a part of this article details step by step how to convert a standalone DB into a Workgroup DB.

Standalone VS Workgroup

          Standalone database

A Standalone database (DB) is dedicated for a single user working independently. All the data from the DB is only accessible to this user. Only this user have all the rights and permissions on the DB. Another user will not be able to work with the data and would only be able to view the data. This part is the first key point.

Another key point is that the Standalone DB must be stored on a local drive of the user computer. It should not be stored on a server or a network drive. If a user tries to do so, there will be no error message. Nonetheless, the user will take huge risks to corrupt the DB, especially if a micro disconnection happens during the commit process.

If a user works independently but wants to store the data on a server or a network drive, the Workgroup must be chosen.

Note: using a Standalone DB is not a break to exchange data or results. The transportable DB will have to be used.

          Workgroup database

Unlike the Standalone DB, the Workgroup database manages multiple users. Several users can have access to the same DB. A conflicts manager allows to securely have several users working on the same network. Moreover, this type of DB allows to securely store data on a network drive or on a server.

Create a new Workgroup database

To create a Workgroup database, there are two steps:

  • Installing the Workgroup Data Server
  • Creating the Workgroup Database

Workgroup Data Server installation

          What is the Workgroup Data Server?

The Workgroup Data Server is a server component, which manages access to Workgroup databases from InfoWorks ICM and InfoNet Clients. The Data Server is designed to improve the performance and reliability of database operations in a Workgroup environment. The advantages of using a Workgroup Data Server are:

  • Less network traffic:
    • Only modified data is sent between Workgroup Client and the Workgroup Data Server.
    • Data is compressed.
  • Better performance:
    • The Workgroup Data Server is the only process accessing the data, so it can be located on a local disk on the machine running Workgroup Data Server.

The same Workgroup Data Server can be used for many different databases. The Workgroup Client (user interface) communicates with the Workgroup Data Server with TCP/IP. The default port is 40000. It can be modified with a configuration file.

          How to install the Workgroup Data Server

The Workgroup Data Server can be downloaded on the same web-platform to download InfoWorks ICM. You must use your own login and password to access the download. For each new version of the Workgroup Client, the same version of the Workgroup Data Sever should be installed. The Workgroup Data Server is available in 32 and 64 bits. We recommend to use the 64 bits version, as for the Workgroup Client.

Workgroup Data Server installation

Once the installation file is downloaded, it should be executed on the machine hosting the DB to install the Workgroup Data Server. Be careful, it is important to install the Workgroup Data Server on a local drive. By default, the installation is done on the main hard drive. This location can be modified but must stay a local drive.

          Workgroup Data Server configuration

It is possible to configure some parameters for the Workgroup Data Server. These options are set in a simple text file called snumbat.ini. The Workgroup Data Server installer does not install a default version of this file. You will have to create it yourself if you want to change the default settings. The file should be located in the directory where the Workgroup Data Server is installed, the directory containing the file snumbat.exe, which is normally “C:\Program Files\ Innovyze Workgroup Data Server”

Note: with standard Workgroup Database, it is not necessary to use a snumbat.ini file. It is used only if you want to change the default parameters.

The following table indicates the key words and values to use in the configuration file.

Keyword Use Value
Port Specifies the TCP port number to listen on. The default value is 40000. TCP port number to listen on.


DataPath Specifies the data directory SNumbatData for the WDS Data Store. For best performance this should be on a local drive. Path of the folder
LogToFile Choose where to find the log output.

The default settings is 0.

0: log output is sent to the ‘Windows Event log’

1: log output is sent to a file called snumbat.log in the root of the WDS Data Store directory.

LogLevel Specifies the log level treshold. Each level adds more details.

The default settings is 2. We do not recommend setting a higher value.

4: errors only

3: includes warnings

2: includes start-up/shutdown information

1: includes general information about usage (to log file only)

0: includes debug information (to log file only)

DisableReverseDNS The Workgroup Data Server uses reverse DNS to lookup the name of incoming connections. If reverse DNS is not setup for your network this lookup might add a second or two to each connection to the Workgroup Data Server. Settings this paramater to 1 will disable the lookup.

The default settings is 0.

0: Active Reverse DNS

1: Disable Reverse DNS

AllowDatabaseCreation Allow the creation of the database.

The default settings is to allow database creation by clients.

0: Creation disallowed

1: Creation allowed

Only the Workgroup Data Server needs to have access to the files in the DB (files within the .sndb folder). For a better performance, they have to be stored on a local drive of the machine running the Workgroup Data Server. In other words, the Workgroup databases must be stored on a local drive on the computer running the Workgroup Data Server (keyword DataPath).

Create a Workgroup database

The default location for the Workgroup databases is C:\ProgramData\Innovyze\SNumbatData. For each database, there is a .sndb folder identified by the name of the database. Be careful, the files within the folder representing the database must not be modified out of the user interface.

Once the Workgroup Data Server is installed, you can create a Workgroup DB from the user interface. These are the steps to follow:

  1. Open the user interface.
  2. Go to File > Open > Open/Create master database…
  3. Choose the type Workgroup.
  4. Enter the name or IP of the server, which will host the DB.
  5. Choose the communication port (40000 by default if not changed in the configuration file).
  6. Click on Connect. A message should indicate that the connection was successful.
  7. Create or browse the database by clicking on New or by choosing from the list menu.

Create database

How to convert a Standalone database into a Workgroup database?

With the following steps, you can convert your Standalone database into a Workgroup database:

  1. Install the Workgroup Data Server on the machine that will be hosting the database. The installed version should match the Workgroup Client version.
  2. In option, configure the Workgroup Data Server to use a different port or the location of the database (by default C drive).
  3. If the point 2 is used, you should restart the Innovyze Workgroup Data Server service.
  4. In the user interface, create a new Workgroup DB (see previous paragraph).
  5. Open the Standalone DB as another database (File > Open > open another master database)
  6. Copy the database objects from the Standalone DB to the Workgroup DB to finish the transfer. You can also transfer data from a transportable DB.

Key points

  • The database types (Standalone or Workgroup) are independent from the type of licence. It is the location of the database and the number of user which will determine the type of database to use.
  • The Standalone database is dedicated to a single user and must be stored on a local drive (not on a server and not on a network drive).
  • The Workgroup database should be chosen when there are several users or when the location of the database is on a server or a network drive.
  • To use a Workgroup database, you should install the Workgroup Data Server on the machine hosting the database.
  • The Workgroup Data Server should be install on a local drive.
  • The Workgroup Data Server is a server component, which allows the communication between the user interface and the database.
Geomod blog, Sailing

An Increasing demand for Port ENCs

The arrival of electronic navigation charts (ENC) in the maritime world has brought a real gain in terms of navigation safety. The use of ENCs enables programming a large number of navigation alerts and provides additional information to those presented on paper charts or their digital raster versions (RNC). The use of ENCs is now pretty widespread and there is a growing demand for the most accurate and up-to-date port ENCs. However, the enrichment or creation of ENCs requires a specific expertise and a technology dedicated to digital marine mapping. As such, we are seeing the development of new partnerships between port services and consulting companies capable of providing both an expertise and a technology dedicated to marine geomatics.


At the end of the 1980s, the arrival of the electronic navigation systems in the maritime world profoundly changes the way of sailing. Coupled to a GPS and based on digital marine charts, the electronic navigation systems enable real time monitoring of ship position on the marine chart as well as supervising a planned route.

The use of electronic navigation systems is quickly seen as a major step forward for the safety of navigation and its usage is formalized in 1995 by the International Maritime Organization (IMO). From this date, all electronic navigation systems respecting the IMO resolutions on the “Performance standards for electronic chart display and information systems (ECDIS)” becomes officially usable to navigate and it may no longer be required to use paper charts.

However, what do we mean by digital marine chart and on what type of digital marine chart should an ECDIS rely to exempt mariners from leaning on a portfolio of up-to-date paper charts? Broadly speaking, we can say that there are two very distinct types of digital charts: the raster charts and the vector charts. Only the vector charts based on the S-57 standard can prevent the mariners, operating a certified ECDIS, from maintaining a portfolio of paper charts.

The Raster Navigational Charts (RNC)

The raster navigational charts (RNC) are paper charts that have been scanned, georeferenced and encoded into a digital pixelated image (e.g. in arcs, bsb or geotiff format). Their resolution and their volume (weight in bytes) depends on the number of pixels inside the image. Higher is the image resolution, higher is its number of pixels and larger is its volume.

The advantage is that raster charts are quicker to produce, since they are no more than a color ‘photocopy’ of the paper charts, to which the cartographer has added some metadata including the chart number, the issue date or the code of the organization that produced it. Of course, this argument holds only if the raster chart is based on an already existing paper chart. Otherwise, it becomes necessary to produce the chart and there is no gain in time. Beyond this consideration, the raster navigational charts have no intelligence inherent in their structure. The use of raster charts has even several disadvantages…

A first drawback concerns the very large volume of data to manipulate and manage. A raster chart uncompressed in Geotiff format can easily reach hundreds of Megabytes (MB), which is considerable for a single chart. As a result, everyone can imagine the volume of a database composed of dozens of raster charts.

A second drawback relates to the charts update. Beyond the large volume of data to be updated, the raster charts structure makes difficult their incremental update and it is often easier to replace the modified charts by their newer versions. In this case, the mariner may no more visualize the differences between old and new charts.

A third drawback refers to the lack of additional information. A raster chart consisting of a single layer of pixels is not queryable. The raster charts do not include additional information or detailed descriptions of each of the objects making up the navigational chart. It also precludes to link these objects to external resources such as diagrams, sketches or pictures.

A fourth drawback stem from the unchangeable nature of the raster chart. Just like a paper chart, it is impossible to benefit from a dynamic display of the information presented, depending on the context of navigation. For example, screening objects depending on the scale of navigation is infeasible. Likewise, adapting the safety contour drawing, separating safe from unsafe waters, according to the draught of the ship is also infeasible.

The last drawback, and not the least, addresses the safety of navigation itself. The raster charts do not allow programming navigation alerts based on information coming from the chart. As such, it is impossible to raise anti-grounding alerts when the ship approaches an area whose depth is unsuitable to the vessel’s draught or when the ship is under way to a particular danger.

The Vector Navigational Charts (ENC)

The vector navigational charts are much more than simple digital reproductions of paper charts. They are structured dataset containing a lot of additional information compared to those presented on the raster ones. In other words, vector charts are not just a mere grid of pixels, but instead a real set of geometric primitives and geographical features allowing the on the fly generation of a digital image whose resolution depends on the quality of the screen on which the image is displayed and on the software that has generated it.

As for the navigation raster charts, vector navigation charts may exist in different formats. It may well include the S-57 format from which are produced the electronic navigational charts (ENC) or the additional military layers (AML). It may also include the “vector product format” (VPF) from which the digital nautical charts (DNC) of the “National Geospatial Intelligence Agency” (NGA) are produced.

The S-57 charts are the only navigational charts to be officially recognized by the International Hydrographic Organization (IHO). As a matter of fact, the S-57 format actually refers to the S-57 standard published and maintained by the IHO, and on which rely upon various cartographic products—the most common one being, from far, the electronic navigation chart (ENC). The acronym ENC denotes the cartographic product as well as a specification also published and maintained by the IHO. This specification lists all of the objects (land area, sea area, bathymetry, aids to navigation, etc.), the attributes of objects (depth value, minimum display scale, object name, description, etc.) and rules that the cartographer must use to produce a proper ENC. The basic unit of the geographical coverage displayed on a screen (the equivalent of a paper chart) is called a cell. This coverage can be composed of several cells or cell fragments. The use of ENCs has several advantages over the use of their raster counterparts…

A first advantage is the reduced size of the cells. The ENC specification does in fact require that the size of an ENC remains smaller than 5 MB. In practice, a cell often weighs much less than this. As such, a set of ENCs is much thinner than a set of RNC.

A second advantage is the ability to easily integrate updates. The differences between the base cell and those resulting from the updates are stored and thus easily accessible. The ECDIS also grants the possibility to create (or remove) its own manual updates. In this case, the content of the chart is not changed. Instead, it just adds a visual artifact.

A third advantage is the possibility of using a customizable portrayal. The S-57 standard applies only to the data structure and does not, in any way, include display rules. The ECDIS display of an ENC is driven by the IHO S-52 standard. However, it is quite possible to apply other types of portrayal. The use of the S-52 portrayal rules is mandatory only if the mariner wishes to operate its electronic chart system (ECS) in ECDIS mode. The S-52 relies on the topology of the S-57 standard to implement display priority rules (e.g. when a geometry is shared by several objects). For any other type of electronic chart system, such as those used for recreational navigation, each manufacturer is free to apply its own display rules. Technically, an ENC may very well be displayed with the same look and feel as the paper charts.

A fourth advantage, still related to the display, is the configurable nature of this display. The user can choose to display any given object according to their preferences. ECDIS happens in fact with 3 display modes, ‘Base’, ‘Standard’ and ‘Full’. The ‘Base’ mode corresponds to the minimum display. Objects grouped in the ‘Base’ profile can never be hidden. The ‘Standard’ mode is the default and recommended display configuration to navigate. It contains all of the objects considered as critical for the safety of navigation. The ‘Full’ mode displays all the available objects. Generally, manufacturers include a fourth ‘Custom’ mode that allows the user to create and apply specific configuration.

A fifth advantage relates to the queryable nature of all the objects making up the chart, giving access to a whole lot of additional information. These pieces of information may take the form of symbology descriptions, depth values indications, navigation instructions, guidance, and so on. It may also take the form of diagrams, drawings, photos and any other types of media available as external data source linked to the queried object—as long as it is packaged in tif, gif, jpeg, txt, or pdf format.

A sixth advantage relies on the configurable nature of the safety contour. Each ship has a specific draught that may evolve depending on its load. It is very useful for mariners to be able to configure this draught in the ECDIS and benefit in return from an adapted safety contour and a suitable differentiation between safe and unsafe waters (i.e. white and blue colors).

Finally, one last advantage, and probably the most important one, refers to the possibility of setting up navigation alerts. These navigation alerts may depend on the configured safety contour as well as the information contained in the ENC. As such, wrecks, obstructions and other dangers, restricted areas, or bathymetry data are as much information that can be used to raise navigation alerts.

An integrated management of the world production (WEND)

The world production management has also significantly changed since the appearance of the ENC. In the past, each producing agency could propose marine charts all over the planet, even if those were overlapping with other charts produced by other agencies. Besides, the responsibilities in case of mapping errors could be somewhat hazy.

Since 1997, the IHO resolution on the “Principles of the Worldwide Electronic Navigational Chart Database (WEND)”, defines the obligations of the producers of official ENCs:

“to ensure a world-wide consistent level of high-quality, updated official ENCs through integrated services that support chart carriage requirements of SOLAS Chapter V, and the requirements of the IMO Performance Standards for ECDIS.”

Accordingly, the producing agencies of official ENCs have found themselves forced to share the global production, so that the mariners may benefit from the most up-to-date ENCs on the largest part of the globe. This resolution helps avoiding ENCs duplication as there may only be one ENC per given area. If the geographical footprints of two cells of the same scale band overlaps, only one of both must contain data on the overlapping area. Cartographers use the meta-objet M_COVR and its CATCOV attribute equal to 1 to indicate an area containing data, and CATCOV equal to 2 to indicate an area of no data.

In addition, any official ENC is necessarily published under the authority of an IHO Member State. Indeed, since the liability of the authority publishing an official ENC may be engaged in case of mapping error, and considering the cost of the damages that may represent the grounding (or the shipwreck) of a ship, it is understandable that only a State may be allowed to take this kind of responsibility.

Therefore, there are two types of ENC: official ENCs produced under the authority of a State through its national hydrographic agency and unofficial ENCs produced by other organizations. It is worth noting that a private company may still be mandated by a national hydrographic service to help in the production of their official ENCs.

Towards an increase of ENC dedicated to port services

A need to enrich the official ENCs portfolio by more specific ENCs was issued by many port services, including French ones. This is, for instance, the case of the port pilots of Marseille-Fos and Nantes – Saint-Nazaire or the technical services of the Nantes – Saint Nazaire Port Authority, the Ports of Normandy Authority (PNA) and the Grand Port Maritime du Havre (GPMH).

However, modifying, enriching or making an ENC requires a very specific expertise in digital marine mapping in order to meet the quality requirements of the ENC specification. For instance, an ENC that does not respect the topological structure required by the S-57 standard may appear correct at first glance, but alter the proper functioning of the ECDIS and Pilot Port Unit (PPU). This type of expertise is generally only available within national hydrographic offices or within agencies specialized in marine geomatics.

In addition, modifying, enriching or making an ENC also requires to rely on a technology dedicated or at least adapted to this activity. It is worth noting that the traditional geographic information systems natively lack features dedicated to the publication of S-57 ENCs and do not implement the quality control procedures defined in the standard S-58.

Therefore, we see that port services are starting, more and more, to develop partnerships with consulting companies able to provide both an expertise and a technology specialized in marine geomatics. This is typically the case of Geomod who intends to support ports services by providing its expertise around the S-57 standard, its  ENC editing software (PortSide), its generator of bathymetric ENCs (Ulhysses), and some custom-built applications (e.g. ePilotBook).

The activity of ENC production support for harbor authorities has started by addressing a request of the Marseille-Fos port’s pilots who needed to integrate the centimeter level accuracy of the port’s topographical survey in the ENCs* used in their aid to pilotage web application based on ePilotBook.  We may well include the Nantes – Saint Nazaire Port Authority for whom 7 “Berthing” level ENCs* have been initiated in order to cover the ascent of the river Loire. We may also include the Le Havre port’s pilots who needed an ENC covering the end of the Grand Canal.

The activity of ENC production support for harbor authorities is now continuing at the request of the technical services of the Grand Port Maritime du Havre (GPMH), that Geomod helps in the production of 15 “Berthing” level ENCs* covering the entire port domain (the port of Antifer, the port of Le Havre, the Grand Canal and the Tancarville canal.

Port of Havre

Port of Le Havre – Géoportail


Port ENC of Le Havre – Geomod

* It should be noted that these ENCs  are “first release” only meant to provide assistance to the internal ports services.

Geomod blog, Land

VigiExpo, or couple smartphone measurements with simulations

The VigiExpo project funded by ANSES (French Agency for Food, Environmental and Occupational Health and Safety) within the framework of the research National plan Environment-Health Work.

A collaboration between Centre Scientifique et Technique du Bâtiment (CSTB)XLIM laboratory (CNRS UMR 72522) and Geomod.

The goal of the VigiExpo project is to develop a standalone monitoring system of population exposure to electromagnetic field generated by mobile telephony base stations antennas. Exposure levels have to be estimated at any point of a given geographical area.

Numerical modelling of the exposure levels allows an analysis of exposure on a large scale and at any place. This is complementary to measurements vigiExpo-schema-enwhich are always temporally and spatially localised.



One of the major difficulties in the production of exposure maps is the knowledge of the precise characteristics of the transmitters in base stations antennas: exact position, power, radiation patterns. Some partial information is available in the public domain, such as the website Cartoradio in France maintained by ANFR (French National Agengy for Frequencies). This information is both partial and imprecise and mandatory parameters for simulation are lacking.

In the VigiExpo project, we combine simulation with georeferenced receiver power levels data measurements on set of smartphones. The simultaneous and complementary use of data from smartphones and simulations allows by backward optimization and statistical processing to fit the missing characteristics of the transmitters. As a consequence dynamics maps of people’s exposure at the scale of a neighborhood can be built.


Simultaneous route with two different smartphones – GPS data comparison (left) and power level received from a UMTS transmitter (right). Visualization in Google Earth.


The monitoring tool is based on an Android application developed by the CSTB (VigiPhone), associated with the simulation software for the propagation of electromagnetic fields (MithraREM) and an optimization algorithm to go back to the precise characteristics of transmitters.The VigiPhone application collects georeferenced received power level. By networking these data and the appropriate optimization algorithm it is possible to complete the numerical modeling and thus to build dynamic maps of the exposure of people at the scale of a neighborhood.

vigiexpo- mithrarem

MithraREM software (on the left) – VigiPhone application (on the right)

A genetic algorithm has be developed to fit the parameters of the transmitters, so as to make the EMF levels modeled by simulation as coherent as possible with the georeferenced information collected by the smartphones.

We use link indicators (Pearson and Spearman correlation) and error indicatos to find the global (minimum / maximum) extremum in a large solution space explored by the algorithm (precision position, databases of radiation patterns, radiated power). The mutation and corssover methods used by the algorithm have been designed and validated to ensure good reproducibility and stability of the results (systematic convegence towards the real parameters and the physical solution).


Positions obtained by optimization (on the left), comparison measure / simulation (on the right)